Wide Wheel aging battery diagnosis and first intervention

We (mostly) all know that as things age they stop performing at peak levels, sometimes replacement is the best solution, but perhaps other times intervention can fix the issue. I'm not one to shy away from a surgical intervention if needed, but if another therapy can work then all the better.

Background

So, while the WW was going well these last few years I've been using it less (favouring my bicycle for shorter trips in and out of town) and its had a few small issues that I've needed to fix (like the seized rear motor, exacerbating the not using it as much).

I noticed however that the battery was "sagging down" more in voltage sooner than I thought it should do as I was riding (you know, that volt meter on the handlebars does have a useful purpose right?) and began thinking that it may be something more than just expectable aging.

I always check the "Watt Hours" (Wh)  shown on my charge monitoring tool (that always remains plugged in between the charger and the scooter), and the Watts needed to recharge are less than what I'd have expected were the battery depleted down to that level of "remaining charge" (as represented by the voltage when riding). For reference, this is the Watt meter I use:

It conveniently shows how many Amps are flowing, the battery Voltage and on the bottom row cycles the left number through 

• Amp hours (Ah)
• Watt hours (Wh)
• Peak Amps (Ap)
• Voltage maximum  (Vmax)
• Peak Watts (Wp)

the right number shows just the current situation of Watts flowing. Its a great tool and I would strongly recommend everyone with an eScooter or an eBike have one of these; you learn a lot from them.

I mean unless you're stupid, then you don't learn anything ....

First step

So I decided to pay attention to the last part of the charging cycles and come on in at the end; glancing at it as I went about my doings around the house.

I noticed that it was 0.18A (that's also 180mA) at one point, then suddenly became 0.00A ... that's wrong as before I've seen it taper nicely down to 0.01 Amps (because I like to watch these things, just like I like to watch the food I'm cooking so I don't burn it).

"Riigghhhttt" I thought, "the BMS is cutting off before balance has completed" ... first step was to turn off the charger (at the wall, in Australia power points have switches on them) and leave it plugged into the charger (so I can monitor the actual charging point voltage as well as the "take off end" that  shows on the handlebar, yes they are different voltages) and wait a while (about half an hour) and then turned it back on ...

bam ... started charging at 0.56A and I thought yep, diagnosis looks right: BMS is shutting down, the full cells settle (after charging) lowering the difference between pack cell groups. The role of the BMS (among other things like discharge protection) is to ensure that charging is stopped before any cell (bundle) is over charged (think fire risk) and to help fully charged cells bleed over to the less charged cells (although different BMS's do this with different levels of quality).

So clearly it was shutting off before the other cells were fully bled.

Not wanting to stand there all day I decided to automate this with a simple "clock work" power timer I had lying around ... 

I set it to provide power for 15 minutes and not provide power for 15 min. I can "turn it on" for the first bulk charge (to save time) using the switch on the side:

in the up position its providing full time power (ignoring the settings) and in the down (blue/green arrow) position its on the timer.

Lastly

I've put together this quick video showing all this and discussing the same points above but in a slightly different angle. 

I hope that together this makes things clearer

I'll follow this up in the coming weeks with what happened and if this simple solution means I don't need to do pack surgery and replace the BMS (with a spare which I'll probably already have on hand from last time).

See Ya

the "scootering dream" vs reality

I love using my scooter, be it for a trip to the shops or just an afternoon ride to the sunset; however one thing is certain in my mind: I have to pay attention.

Scooters (and the idea) are sold to people as some sort of dreamy fantasy

beautiful bright future city-scapes and people dressed neatly and smiling, no crowds on sunny days ... its idylic, even pretty chicks can do it looking fashionable and hot.

The reality however is usually obscure obstacles that didn't stand out to your untrained eye

but when you get down to wheel level and look will be sufficient to off you with your itty bitty wheels ...

when you hit them without looking and going fast (see this post). 

Often they can be hidden under leaves or small debris:

so the rule is: if you can't see it suspect it.

Hitting small (you thought) insignificant obstacles which in combination with the itty bitty wheels of scooters your daydream ride may turn in to this

even at speeds that (if you've only been in cars) seem not fast ... the reality is however even a basic scooter goes faster than you can run and if you trip while running full speed you'll also risk injuries like the above.

Scooters should be ridden by a rider that respects these facts, because scooters can be dangerous, especially when going fast.

Remember, the only thing that really matters in safety is YOU. Scoot so that you can scoot again tomorrow and enjoy the future days

not so that you spend the rest of your life coping with injuries.

Maintaining the effectiveness of your tyre sealant

The following is sort of a journey of discovery that has come from my using Slime in my MX60 as well as examining Slime and comparing it to other products. The focus of this post is about Slime.

A UK based MTB enthusiast friend of mine (hey Leadville) uses Stans in his MTB and in a recent discussion about the dealing particle size and density we had I became more interested in this product. Anyway, I was reading the label and found this guidance:

So the hint about arid climates and drying piqued my memory. Should be no surprise because Stan like slime Slime is water based (as are they all).

Now I recall how when I changed my tyre last time that the Slime was all clagged up on the inside of the tyre, and I recall too how easily it dissolved putting the tyre into a tub of water (in an attempt to clean it). Thinking about this made me soon realise that the wheel spinning (often doing 30kmh) is acting as a centrifuge, which is commonly used to separate out things suspended in water; and quickly too. See this video:

BTW, if you're not seeing the videos, then either use a computer (not a phone) or put your phones browser into "Desktop" mode because to be frank much of the internet doesn't work on phones. Even youTube is still a better experience on a desktop setting.

Which isn't ideal for how the product was intended to work and indeed may also be part of what Stans is getting by replenishing.

So as I'd previously done an experiment with adding "cheapo-slime-alike" into my tyre because I noted that it benefited from being bashed around and refreshed with some of the cheapo stuff

Towards the end of that I mentioned also that I bashed the tyre with a hammer ... So I thought I'd do a blog post consolidating all that and showing what I did on a youtube video.

In summary, what I do is:

1. let the tyre down (by removing the valve from the stem)
2. insert water with my syringe
3. bash around the circumference of the tyre with a hammer to loosen off any slime caked in there
4. give it a quick spin and a sudden stop
5. re-insert valve into stem and reinflate
6. take if for a ride

So ultimately this now seems to be the best way of making the most out of slime

PS: this is the result of a weeks drying in a glass with a lid and then re-hydrating with a few drops of water

Widewheel battery durability testing (revisited)

 I enjoy riding up and down the local mountain road. Its not only a very pleasant escape but its an excellent opportunity to test the battery and how its shaping up.

Now its worth while remembering that I bought this scoot in July 2019, which means its nearly 2 years old. In that time I have followed the following principles of battery handling

1. always fully charge it (some minor exceptions exist)
2. use the scoot soon (within a day) after charging
3. do not recharge if I know there is sufficient charge to make the trips I'm intending (frequently I do three or four 3km trips in a day)
4. it has been charged at 4Amps since I bought the fast charger in Jan 2020

So over the last (nearly) 2 years this equates to about 312 full charge cycles in its use.

The Test

Load testing of batteries is the best way to determine their health and their current capacity. Usually load testing is done on a bench with tools to map out the battery performance (represented by voltage) under a stated load. Since people are often confused by data that's about each cell (the 18650 cell) that comprises our packs I've annotated this graph with the voltage that a pack of 13 cells in series would show if tested this way

So yes, its normal for voltage to drop over the discharge of it. Importantly this is for a single cell, and discharged at 2Amps; as my pack has 6 cells in parallel for each cell to get 2A sucked from it the motors would need to be sucking 12A out of the pack (cos 2 x 6 = 12 right?). At 48V that would amount to something like 500W on the flats to do 25kmh. which is a pretty reasonable estimate of the power . Then given an 8% grade which my parameters indicate that to keep average 23kmh up an average 8% grade will need 743W. Suggesting that on the climbs I drew more like 2.7Amps per cell.

So its ball park and a good actual real world test

To refresh you with the course the distance and elevations are:

Basically I did that route again. 

Rather than record the whole trip again I decided to record just the most important parts: the slug up the hill from the bottom of the steep climb up to the top.

This clarifies the grade of the climb, the length and that the scooter just hauled up with almost no change in speed. Impressive on a 2 year old battery. 

The return voltage was 46.4V which is almost exactly what I'd got in the past and charge required 406Wh to refill which is almost exactly what I've got in the past.  This means that over 26km I consumed 406Wh which is 1.6kWh/100km (15.61Wh/Km) or almost exactly what it normally uses (no surprise there either).

Points to consider on this I went up to Johns (adding a couple of km of uphill) and on the way up to Queen Mary I had a tail wind (which would have assisted somewhat). On the way down (of course) I had a head wind, but for the steepest parts the speeds were still sufficiently high that back EMF would almost fully negate any additional power demands for that.

Previous results

This test was pretty much a repeat of many tests and probably the best reference is this one from May last year, back then I determined there was no appreciable loss. Another test run worth a look at was this one (where I dug into more figures)

Conclusions

So given that this scooter is two years old, and has been (as mentioned above) fully charged when cycled (but usually no less than 40% before recharge) and is still performing within all practical intents as new. This is not unexpected and something which I explain in this blog post here. I've got further discussion here and here.

So the next time your on Reddit and some pack of fully ignorant-kiddie-wankers go on about killing your battery by charging it fully (NB using it as designed) ... just ignore it ... there is no evidence other than the clear evidence that they're idiots.

help me choose a scooter

One of the most common questions is:

Help my choose a scooter

Really there's so much personal in that but if you strip away your own desires for how it looks and focus on what you need of it (performance) then you can set yourself up pretty well for dismissing lots, leaving more time to enjoying life on your scooter (rather than fussing about what to buy with no actual criteria to help you).

I wanted something which could fold and fit in my car, not break my back putting it there and climb the hills around where I lived. I ended up with this

So what you want it to look like aside, to me the best you can hope for is to use your own understandings of physics and make some educated guesses based on specs.  Weight of the scoot is pretty straighforward, but what's often difficult is "range and speed" (and often forgotten is hill climbing).

For instance its well understood what energy is needed to get a human body up a hill on a 2 wheeled machine, cyclists have been into this for decades and there are good online calculators: I've used this one. Those are actually my parameters and have proven very consistent in estimating my scooters (all of them). About a year back I put this blog post together to understand my scooter (then the 500W Mercane single motor) and then estimate if the 1000W dual motor (otherwise the same as the single) would give me better hill climbing (speeds on the flat were essentially firmware limited to comply with the law) and be worth my while buying.

For instance in my parameters above I picked 8% because that's not steep:

... Maximum slope for hand-propelled wheelchair ramps should 4.8 degree angle or 8.3% grade. Maximum slope for power chairs should be 7.1 degree angle; 12.5% grade.

my driveway is more than twice that and so is the top of my street. So I needed more and so plugged in higher numbers into that calculator above and it was pretty clear what I needed.

Plug in your own weight and see what you should need in terms of battery capacity even for just "regular riding" (meaning not climbing steep hills if you don't have them). You'll also see that as you go faster (even on a flat) more power is needed, its not a linear relationship (meaning that to go twice as fast you need a LOT more than twice the power). Power is best measured in Watts (unless you ride horses ... then I suppose Horse Power makes some sense).

Next you'll put that requirement (of power) into a simple calculation of how many Watt hours (its simple because if you use 400Watts to maintain a speed for an hour you'll need 400 Watt hours (Wh). The faster you want to go the more Wh you'll use (even per distance) because physics is a harsh mistress, you can dream any wanking you like, but she won't let you live it out.

My Mercane Widewheel cost AU$1400 weighs 24kg and has a 633Wh battery. However the reality is you can't get more than 70% out of a battery (without probably walking) and you probably shouldn't run it that flat often anway. So that means a usable Wh from my battery 450Wh ... which I don't usually push it that deeply (but go close).

That'll allow me to do this, and learn from that to make this estimate of 1.96kWh / 100km  As well as informing me about how to make further decisions. 

So from this you should now be able to make some informed decisions about what power you need and how much battery capacity you need for that task (and your range).

In contrast my Mercane MX60 has a 1200Wh battery (which for a reality check is not far from the size used in a Hybrid Car), the scooter cost me AU$3000 and gives a usable range of 30km (probably more if I was willing to risk having to push it and go slower). But at 34kg its bloody heavy to lift and I seldom take it anywhere in the car (and thank Gawd that my house is low set or it wouldn't even be an option), which I indeed do with the Widewheel. I mainly use it on the weekends now as I actually don't like the fact that its so much higher than the widewheel, even if it cruises bumpy roads better.

So everything is a trade off, if you want more power you'll have a bigger thing (kids today probably don't work on engines of cars anymore and so this is perhaps not obvious):

If you want to go faster you'll need:

• more power
• bigger battery (to deliver more power and longer if you want any range)
• better suspension
• better wheels
• stronger chassis
• good steering dynamics (better read this, scooter folks seem ignorant of this point)

and that will cost you more money and a penalty of greater weight (because physics is a harsh mistress).

Next we come to the old chestnut of tyres; I was 100% clear (after many years of bicycles and motorcycles) that I did not want pneumatic tyres on my scooter for work commuting. Flats are inevitable and and more pronounced with smaller wheels and much harder to fix with smaller wheels.

I subsequently bought a scooter as a "fun thing" which did have pneumatic tyres (the MX60 above) and in less time I've changed more tyres and had more struggle with that than the entire amount of time spent on the Widewheel.

think about that...

Thus we come back to the beginning where I suggested "focus on what you need of it" not the wanking of how it looks in pictures. Ask yourself:

• will I need to carry it (or push it)
• do I need the range (if yes perhaps look carefully at an eBike or (gosh) a motorbike)
• how much am I willing to spend (as much as a motorcycle)?

Lastly (hopefully you read the other ones), I recommend you read these two about scoots and reality, and then read this post for thoughts. It will perhaps help you to understand your needs and see the experiences of somone who has probably used a bigger variety of 2 wheeled transport for quite some time.

Teach a Man to Fish ... Time for a beer I say, and I know which scoot it'll be that I take ;-)

Happy Scooting

scoots and reality

I've got two things I call "my scoot" (well 4 if you count my Widewheel 500W, 1000W and the two pictured)

Interestingly they both cost the same amount to buy, but there are differences.
LHS = left hand side
RHS = right hand side

• LHS is a month old and has under 700km on it, RHS is 13 years old and has 128,706km on it (almost comical isn't it), I anticipate at least another 40,000km while I seriously doubt that the LHS will ever mange 10,000km
• RHS one lives outside rain hail or shine, LHS would be dead soon if expected to do that
• LHS doesn't work well in the rain, RHS been ridden plenty of times in pouring rain
• LHS has a top legal speed of 24kmh and a top speed of 55kmh, RHS has a top legal speed of 100kmh and a top speed of 160kmh
• LHS really only good for short around town trips while RHS does everything from long highway hauls to nip up to the shops
• LHS has questionable insurance cover for personal injuries RHS has full and proper insurance for that
• operating costs of LHS unknown expect depreciation to by the killer, doubt that it'd do 10,000. Meanwhile RHS has oil changes every 5000km (costs me about $40), oil filter changes every 10,000km (adds $15 to oil change cost), belt change every 40,000km 
• RHS I could ride 2,000km tomorrow if I chose to, LHS its not even a laughing matter to consider that without a steady stream of stops to recharge every 50km (assuming I only do 27kmh (taking 10 hours, so overnight) so LHS is not even remotely a long distance touring machine
• recharge LHS costs 1c per km RHS = 7c per km
• recharge time for LHS is over 12 hours (with standard charger), which might be able to come down to 6 with a high amp charger, RHS is about 5 minutes at the servo

A quick demo of the T-Max

Some years ago I wrote this post:  Do electric scooters dream of being petrol powered?

things are perhaps a bit better now ... but not by much.

If I have to go to the next town I know which one I'll take ... heck if I was still living in Brisbane and I wanted to go to the next suburb I know I'd take the T-Max. 

Motorcycles are simply safer in traffic with cars than scooters are, don't let your fantasies give you injuries.

steering trail

Steering geometry is a pretty well studied area, and hapilly few motorcycle or bicycle riders need to give much thought to it (although the advanced riders certainly do) because ... well because the best riders already have, and have worked closely with the engineers and makers to make sure that everything is done right. Its pretty well understood these days (like the last 50 years).

Sadly most of the the eScooter community is entirely ignorant of it and the internet fora are of course rife with fools and idiots who know a few buzz words (or don't) and dismiss this idea as etheric.

This results in the perpetuation of unsafe scooters on the market.

In short, trail is the distance the contact patch is behind the steering axis (just as in a castor wheel on a shopping trolley or office chair) on a Scooter it looks like this:

The angle down is called by some the "rake", this angle helps but trail is the main factor in stability (like a castor wheel).

Now this is a common amount of rake and trail on a modern MTB

yet on many modern and fast scooters the amount of trail is dangerously small, such as this Zero which is almost nil:

In contrast both of my scooters above (the Widewheel and MX60) have quite well designed amounts of trail

... meaning that I can briefly let go of the handle bar to (for instance) hand signal a turn, for instance even at high speeds the steering is quite stable:

While many scooters (such as the zero above) are so inherently unstable people consider "steering dampers" for them.

My Giant MTB for instance has the following spec published on the Giant Website:

although what is called rake here is probably offset, and another meaning of rake is the angle that the forks are raked at (which influences flutter of the wheel or better known as wobbles).

Meanwhile eScooter riders wet themselves instead on top speeds and the "advanced" riders know fancy terms like "steering damper" (which essentially means bolt on fix for shit geometry). So as I said at the start, well understood and a published spec in the bicycle world and in the motorcycle world too ... just not in the advertising mush or reviews (don't start me on how miserable and technically ignorant most reviewers usually are).

For the interested I'll leave you with some good articles to read up on this:

The obvious one is this https://en.wikipedia.org/wiki/Caster which soon leads to an issue of flutter:

One major disadvantage of casters is flutter. A common example of caster flutter is on a supermarket shopping cart, when one caster rapidly swings side-to-side. This oscillation, which is also known as shimmy, occurs naturally at certain speeds, and is similar to speed wobble that occurs in other wheeled vehicles. The speed at which caster flutter occurs is based on the weight borne by the caster and the distance between the wheel axle and steering axis. This distance is known as trailing distance, and increasing this distance can eliminate flutter at moderate speeds. Generally, flutter occurs at high speeds.

which naturally leads into: https://en.wikipedia.org/wiki/Caster_angle#Two-wheeled_vehicles

and finally: https://en.wikipedia.org/wiki/Bicycle_and_motorcycle_dynamics

If you have not yet chosen a scooter I hope this article has opened your eyes to an important aspect of scooter safety.

Happy and Safe scooting

Mercane Dualie Range Testing

A lot is written by people on forums about how charging up to 100%  is somehow harming your battery. I've got posts on that subject recently here. Basically my answer has always been simply: no.

So since I've had my 1000W Dual Motor Widewheel I've basically always charged it to 100%, and usually discharged it to between 50% and occasionally fairly deeply before recharging it. I'm a big fan of evidence and if this fluff idea held any real world water one would expect to actually see such losses.

To actually answer this question I thought I'd take the scooter out for a run to see how it went. This is that run GPS data:

Now as it happens you can add another 1.5km onto that because I went over to visit a mate this morning on it (up a hill most of the way), meaning at least 25km traveled,  and when I got back the Voltage was still over 45V under load and settled to 47V as soon as I stopped and unloaded the battery. This indicates it had a bit more up its sleeve.

Charging has yielded the "consumption" of 387Wh (based on the 150A meter measuring input to saturation) which means that 25km consuming 387Wh = 16.4Wh/km or 1.5kWh per 100km (or pretty much what I observed here).

Now this is under "full power mode" and with (as you see) some hill climbing too (so not just perfectly smooth flat pavement) and if you watch the video of segments of the ride you'll see with a head wind much of the way as well.

When you consider that since I've had it its been recharged between 2 and 3 times per week since I've owned it (so for about 10 months) and returned at least this result on this , this, and this occasion then I think that IFF there is any loss its only found on bench test equipment.

This to me suggests to stop worrying about pointless shit and just ride your scooter.

My observations are that spending that time on actually servicing and inspecting the scooter will make a shit ton more use in extending the life of your scooter.

I look forward in any comments to a rigorous and detailed real world demonstration of evidence to the contrary.

So The King is Dead ... long live The King

cell obsessions

One of the thing I often find is that: the less one knows, the more everything is clear (and the "name" brands are simply better). This seems to carry through with scooters where people come to the topic usually knowing absolutely nothing about electronics (worse, perhaps some odd incorrect ideas) and then start to learn a few things and then tuck that away as "known lore" ... often its not based on science or engineering. The cells in our batteries is one such topic where debate and passion often rages about "LG cells" (rarely Samsung or Panasonic) being the pinnacle.

I do try to say that whatever the retailers claim (and you believe used car salesmen too?) as its sealed in a shrinkwrapped pack you just won't fucking know unless you strip it back (probably voiding warranty) and look for yourself. I'd say almost none of the vocal Wangers ever do this.


While I was doing my various stages of repairing my 500W single motor battery pack I posted (in here) that I had found what I think was the cells used in my pack.

From this blog post I wrote:

this makes me wonder if this is the newer chemistry with Nickel in it?

INR - NMC - Lithium manganese nickel

The reigning champ of the 18650 vaping world. This chemistry adds nickel to the IMR chemistry above, making it a "hybrid" chemistry. It combines the safety and low resistance of manganese and the high energy of nickel.

The resulting battery chemistry gives you a reasonably high capacity and a high discharge current. Importantly for vapers, the chemistry is very stable, meaning that you don't need expensive built-in protective circuits. 

There is extensive innovation within this chemistry as well. Sony, Samsung, and LG are all developing next-gen INR batteries with different ratios of manganese, nickel, and cobalt. 

which when I examine this in context of the earlier mentioned blog post it becomes very informative.

Also, a little web  searching revealed this test on what appears to be the same batteries. I think its reasonable to believe that they are more or less the same as the cells that are in my pack. His conclusion was:
Conclusion
The cells looks fairly good, they are obvious not for 30A, but 20A looks fine.

So that site (lygte-info.dk) has that excellent tool for making comparisons. Since I can't share such a link here's a screen grab of the Parkside battery beside the ("Famous") LG branded one.

Now I actually used that image for a different discussion (I'm into reuse) and the red line from 3.5V shows the point where its performing under load (riding along, probably up a mild hill) a little while into your ride. Now I notice many people seem to have forgotten how to read graphs (so pardon me spoon feeding here) but the LG battery falls to the same voltage as the Parkside does nearly half an amp hour sooner.

Now that's per cell, and recall that our batteries are composed of many cells in bundles (please see this post for details) and strings, however what matters here is the P bundles for the Amps. We often have 4 (or even more) cells in this bundle. So for each cell to be needing 3A with 4 cells that would mean you'd be pulling 12A out of the pack (3 x 4 = 12 right?) which is entirely possible with (say) a 500W single motor scooter (usually 1000W motors have bigger P in their battery config).

So in the above the Parkside delivers better Volts well into the ride with less of a slow down (remember V = speed) until just before failure.

Pretty good isn't it. Even better my observations (and calculations) have shown that my own yield from my Mercane battery pack is pretty consistent with the better red curve of the Parkside. Further the only other thing is how many cycles you may get, and I can say that after nearly a year of frequent riding I find no observable (based on distance, speeds and GPS data) degradation in my battery pack.

Case in point, I was riding it around yesterday (well and the day before) and had done over 20km (some of that on ludicrous mode and pushing full speed on down hills) and observed on the way home that the voltage was buckling down to about 44.5V suggesting to me that it was time to recharge. Now even though the voltage popped back up to 47.x when stopped, don't be fooled, that's not how batteries are measured for discharge. So I put my 150A inline and recharged. It took 8.61Ah to charge. Looking at the curve from the site at lytge-info and applying my numbers we see this:

• approximate discharge based on observed voltage was 10.5Ah
• my recharge was actually 8.6Ah
• given the above cell is 2000mAh not the 2200mAh my cells are this more or less accounts for the difference and 
• given that I was discharging at an unknown rate (probably higher than 6A understanding the Watts required for the speeds) it works out about right

Not bad for a pack that has had at least 100 cycles of 100% recharge (if like that even matters compared to other factors)

So play with that comparitor tool and check out some batteries, go price them and then decide if what you have is a sufficient cost benefit for you. After all some people want to balance how much they spend... looking at the discharge curves, frankly I'm glad I don't have LG cells and instead have money in my pocket. A year later and evidence shows there's nothing wrong with what was in the scooter.

should I fully charge my scooter or not?

This is an often asked question on forums and results in much discussion, many seem obsessed with preserving their battery on their new scoot. Makes sense, I am interested in not harming mine also.

First, the Short answer:

To me the simple answer is: YES you should.

Details

The devil is always in the details right?
First and foremost you should always examine any answer and check it for veracity. If nothing else I expect anything I write to be a good jumping point for your further research ... if you have doubts.

Now lets examine the proposition here because it relies on people assuming that the makers are stupid (and some unknown twit on the internet is a genius) and then having just enough knowledge to be dangerous. Perhaps there is also some problems here in that some of these self assessed geniuses may be best described in this blog post, but I digress.

Battery and Cell are used interchangably in common language, yet the dictionary is clear:

There in lies an important difference and one which is probably the root of many misunderstandings.

The Cell

The problem (and why people say you shouldn't charge your batteries fully) is based in this often cited Battery University article where discussion centers on cells (that's individual cells and not even restricted to 18650 cells that our scooter packs are currently composed of) were stress tested and a finding was published.  It starts by showing the results of high discharge rates of a particular chemistry (of which there are a few that continue to evolve).

Now, lets look at what they wrote about this:

Figure 1 illustrates the capacity drop of 11 Li-polymer batteries that have been cycled at a Cadex laboratory. The 1,500mAh pouch cells for mobile phones were first charged at a current of 1,500mA (1C) to 4.20V/cell and then allowed to saturate to 0.05C (75mA) as part of the full charge saturation. The batteries were then discharged at 1,500mA to 3.0V/cell, and the cycle was repeated. The expected capacity loss of Li-ion batteries was uniform over the delivered 250 cycles and the batteries performed as expected.

The graph Fig 1 is as below

To get more than 4v out of a cell we arrange cells in strings (called series) to go to higher voltages. The voltage is simply just the addition of how many cells you make in the series. Like this

Now the reality of our battery packs is that they are not strings of single cells because each cell only has about 2 ~ 3 Ah, while we'd often like more like more than ten. So they are in fact composed of strings of bundles of cells:

1. parallel bundles of cells to increase the available Ah (typically 3, 4 and 6 2,200mAh cells giving 6.6, 8.8 and 13.2Ah)
2. these parallel bundles are arranged in a string (seen above called Series) to increase the available Voltage, such strings are often 10, 13 and 16 (36V, 48V and 60V) because the "nominal" volatage of a cell is usually given at around 3.7

This is normally given in an abbreviated form like 10S3P or 13S6P or something like that depending on your specific battery (I have 3 scooters with 3 different battery configurations).

Now, to replicate their outcome you'd have to discharge your battery solidly with no break, no let off at the same rate. Meaning if you have a 4P configuration. So you'll have to ride your scooter so that the motor draws 6.6, 8.8 or 13.2Amps unrelentingly till its dead.

I'd argue that's not only not what happens, but probably possible without something else failing.

Next that article goes on to discuss another aspect, depth of discharge and fullness of recharge. They state the following:

In terms of longevity, the optimal charge voltage is 3.92V/cell. Battery experts believe that this threshold eliminates all voltage-related stresses ... Most Li-ions charge to 4.20V/cell, and every reduction in peak charge voltage of 0.10V/cell is said to double the cycle life. For example, a lithium-ion cell charged to 4.20V/cell typically delivers 300–500 cycles. If charged to only 4.10V/cell, the life can be prolonged to 600–1,000 cycles; 

Seems compelling,  however then it says:

On the negative side, a lower peak charge voltage reduces the capacity the battery stores. 

... so you want to have high capacity cells (to make high capacity batteries) but then not actually have high capacity batteries anymore so that they may last longer? This becomes more clear when you look at table 4 and its notes:

and pay attention not just to pick the bigger cycle count, but to read the details, like the "Note:" in the middle over there and to Experiment: making reference to to vehicle (meaning cars) at the bottom, and in among all that TLDR writing.

So to get longer cycle life (defined by what?) you need to reduce the capacity as well as the power of  the battery (recalling power = Volts x Amps).

Personally I love the extra power that my scooter has when 100% charged.

I see many people asking about how to get more power from their scooter, so its pretty clear that the answer can't come from under charging.

Next in reading the details you'll find this:

Discrepancies exist between Table 2 and Figure 6 on cycle count. No clear explanations are available other than assuming differences in battery quality and test methods. Variances between low-cost consumer and durable industrial grades may also play a role. Capacity retention will decline more rapidly at elevated temperatures than at 20ºC.

 ... so maybe its not as cut and dried as these studies suggest and then (importantly) will you ever be riding it in summer because temperature plays a bigger margin?

I encourage you to not just skim through that article cherry picking but to really dig in deep if you want the actual answers. If you do you're going to find that this is a very complex subject and has a lot of parameters such as but not limited to:

• temperatures
• chemistries
• cycles of depth 
• starting charge
• duration a cell is held at a charge
• discharge intensity

Are you yet getting the picture that everything is a trade off?

Moving to a battery not just the cell

Now lets consider the actual practical issues in charging our batteries (an array of parallel cells in bundles in a string of bundles) and note that it would be pretty much impossible to charge  all these without a Battery  Management System (BMS) which then distributes the power to each of these. This is the BMS in my battery pack.

Now this is a composite of two images, seen from top and side. The BMS is connected to each bundle so that it can be charged individually. Without this such a system would pretty soon go out of balance and be useless.

Balance?

Yes, each set of cells needs to be not only the exact same chemistry and rating but needs to be at the same voltage when charging is completed, if we just wired these all up and applied 54V across the pack then maybe (maybe) in the beginning it would be able to be completely charged in a uniform way with no cell being forced over the 4.2V and coming to harm (like exploding). This is why its simplistic to just think of that black box that plugs into the scooter as the charger. Its actually not the charger and the BMS is the charger. It makes sure that when any bundle reaches 4.2V its ceases charging, to protect it (and you).

However the reality of this is that because nothing is identical  (and less so with age) not all cell bundles come up at the same time. Were the BMS to just shut down when the first bundle reached 4.2V then pretty quickly the other bundles would fall behind and not have the same capacity. This will result in the pack not being able to deliver its rated output. (disappointing)

Why? Well this is because one of the other functions of the BMS is to protect the cells, you see not only is charging too high a problem but under voltage from "over discharging" is dangerous and can harm a cell. The BMS does this by sensing all the cell bundles Voltage and then shutting down the power output (like an off switch) when any one of the cells falls below its low voltage threshold (often 3V).

Lets examine my pack (which I pulled apart because the BMS was not doing its job, but lets get back to that point soon), when I pulled it down I got the following voltages from each bundle:

You can see that bundles 2, 5 and 11 are significantly lower than the others and bundles 1, 3,4 and 10 are higher.

So this pack was unbalanced and resulting in the following symptoms

• when BMS shut off charging, scooter display showed 54.4V but unplugging it that fell instantly to 52V (some would cheer saying this was good as it wasn't charging to 100% (52 divided by 13 is 4V which would seem good to the less well informed). lets get to why in a moment.
• BMS would trigger a pack shutdown before full safe discharge range was reached because the lower cell (bundle 5) would be exhausted and fall below the critical voltage before the other cell bundles. The BMS is then preventing the cells in that bundle from being harmed by excessive discharge.

So why didn't the BMS bring all bundles up to the same Voltage? Well that requires an understanding of how a BMS works, which is a lengthy blog post in itself, but just keep in mind the following things:

• the BMS can be Active or Passive. A passive BMS can only bleed power from adjacent cells  (so like bundle 2 could get power from bundle 1 or 3 depending which was on its negative side) while the Active type can continue charging individual bundles longer. However all BMS have limits (and trade offs), read this article if you're keen to learn more.
• many BMS have a limit on the voltage difference which they can cope with for some thats 0.2V ... meaning that if a bundle is greater than 0.2V different to the higher ones then its left behind.

My original factory fitted BMS was a Passive type and I changed it for an Active type, happily the pack quickly recovered giving 54.5V soon (in recharge count) after fitting the new BMS. To nudge it in the right direction however I balance charged it manually first.

which of course took some hours of time ... because I had to recharge each of the 13 bundles.

Why did my pack become unbalanced? Well I'd say there are a number of candidates:

1. I think my pack behaved like this (dropping to 52V instantly after unplugging) from when I got it. This may have been caused by the dealer I bought it from allowing some people to test ride it (and the tyres showed that to be the case) without fully charging the battery to 100% out of the box. This is a bad thing and should not be done no matter how much of  a worry-wart-fusspot you are. These things need to be done to ENSURE it starts out properly fully balanced on the first "grooming" of the chemistry.
2. I on a number of occasions was impatient to get going and gave the battery a charge to nearly full and then went on longer rides (like 12 or so km) to go shopping
3. The BMS may have been faulty or a poor design type of passive BMS

Either way it happened and its fixed.

Conclusion

As you can see there's more to the entire question than the simple "don't fully charge it" as there are many trade offs. Most of the literature focuses on where the "real money" is and that's cars. Cars which like Tesla have over seven thousand (7,000) cells inside, not 30 or 72 or even 128. Given the cost of a 18650 cell at about US$3 that means there more than $21,000 in just 18650 cells in a Tesla and you can buy an entire battery pack for a scooter for about $200.

Ask yourself these questions:

1. are you fussing over nothing?
2. are you suffering from new buyer fussing?
3. might you do more harm to the pack by imbalancing it than potentially preserving the cell life
4. didn't you want more power anyway?
5. didn't you want lighter?
6. in reality how many cycles are you likely to do? Do you run out of charge so often that you need to charge more than 3 times a week?
7. how can you control temperature in a scooter?
8. everything has a life span

and a perspective from a well known battery builder:

Lastly to me the low hanging fruit is exactly as said in this video: fully charge it, preferably timed so that its ready just prior to use. Then get the usages out of it and when its at about 30% remaining, charge it. This will minimise the charges, minimise the time at higher voltage and result in the maximisation of cost, benefit, and enjoyment.

So yes, I almost always fully charge mine when I charge it and so far its done over 1000km and based on final charge voltage and range tests (which are a pretty good indicator of battery status) the scoot will still do the same ranges it did from new.

HTH

Off the mark drag race

I've been of the view that off the line the MX60 is no faster (indeed feels a little less snappy) than the Widewheel. I've put this down to the larger diameter wheels (just over 11" vs just under 8") it has the same diameter armature and magnet rotor, which will essentially gear it higher (because leverage right). This will assist its top speed which is unquestioned (because bigger battery Voltage and higher diameter wheels).

I did some quick runs first and found that the speed limiter kicked in on the Wide Wheel earlier than the end of the run (which was about 100 meters) confusing the issues, so I turned off speed restrictions on the Widewheel for this test.

So first some data from my GPS app:

The dip in the middle is a turn around point, which my App didn't log neatly, so lets just work with take off. To me it looks like the initial hit of the Widewheel is a little steeper. Overlaying them we can see it is perhaps a little, but its close.

But this app isn't ideal for such comparisons, so I thought (in case) I'd video it and compare side by side. This is that:

This seems to show that the Wide wheel does get that initial  kick going and leads by a nose for a short time, until the MX60 starts hauling it in. Which translates to "it feels stronger" off the mark. This is not unexpected when you consider the way electric motors deliver power and the effect of the effective lower gearing of the Widewheel (discussed above).

As you can see from this figure above the motive force of the motor is strongest when its stopped and gets to a point where it starts falling off in torque soon after take off. Of course since torque is the strength to do work and power is how quickly that work can be done, the more the RPM increases the more that power increases even though torque falls away.

Eventually however the electric motor spins fast enough that back EMF overpowers the foward voltage provided by the battery and you end up with nothing.

Conclusion

So as I've been saying in my ride dialog / blabbering, the MX60 is really a great "cross town" blaster, especially if you've got a number of nice long "bicycle paths" to reduce the stop starting. In theory you should not be riding at over 25kmh anyway, and so the Widewheel will keep up with all but the most serious Lycra Cyclists.

For those not restricted by (or not interested in obeying) such laws then the MX60 will outpace everything else around you except cars.

As I found on my recent video comparison between my Widewheel and MX60 the MX60 uses more juice than the Widewheel on the same trip as a percentage of the battery. Given how much more power that is in Watts it translates to much longer charging times and or much more powerful chargers.

I've got a 4Amp charger for the Widewheel, which nicely charges it (s 13Ah) battery up from 50% in less than 2 hours. To do the same on the 20Ah battery on the MX60 you'd need more than 6A and to be comfortable with such a flow you'd really need to be confident that the charging wires are up to task.

I personally thermally checked my Widewheel for signs of problems when I first bought that 4A charger. I'd need to do the same with the MX60.

As always more power comes with more costs (both time and money).

HTH

tweaking up your charger

Warning:

Firstly I don't recommend this to anyone who is not comfortable with electrical work and who has no history of electrical work.

So with that out of the way its pretty common that the chargers supplied with our scooters are not really "dialed in" to voltage (you're shocked I'm sure that a charger that you can buy on eBay for $20 wasn't bench adjusted) ... sure someone does some "gross adjustment" but not really careful dialing in (and don't start asking about the accuracy of the 240V supply to your house).

Why?

well as it happens batteries need a particular Voltage to charge, which must be a bit more than the voltage you want them to charge to. It doesn't need to be by much but it does need to be more. Further a reality of electronics is that everything (no matter what) takes some voltage out of the circuit, so even if the charger is supplying 54.4V the BMS will inevitably take a little nibble out, as will all the wires. So its best to tweak the supply to be a little bit over the level of the BMS.

Below is a picture of my charger now charging (in the final phase) my 500W mercane which has ridden just a few Km after its last charge (which I noticed wasn't getting up as far as I'd like it to have gotten) on the "other charger" which I keep at work. I've tweaked all my chargers here.

You can see that while the light has gone green indicating (to those who think they are in the know) that charging is complete, the charger is still supplying a small current (for the saturation of cells to 4.2V)  which still (because of the voltage) amounts to 7.1W or the equivalent of a modern efficient bulb. All in all the battery has had pushed in about 40Wh, which is pretty consistent with the small running around I did before putting it on charge now.

What did I do

Basically I just carefully opened the charger (mine has screws under the bottom rubber feet) and then identified the "trim pot" and with it plugged in and live adjusted that up to where I wanted it. See this Video

This basically went very well and I was then able to see good charging voltages and indeed show the difference between what the handlebar volt meter shows and the voltage at the entry to the BMS (using my inline meter)

Job Done

Hope that is helpful to someone.

Mercane single motor 8.8Ah battery range test

This post is a follow on from my repair post here. Well, looking at all this I'd say that my scoot has passed its battery test. and is pretty much "up to spec" despite nearly a year of use and some problems with the BMS and construction.

Introduction

To test the battery in the scoot I took it on this course:

So while I didn't tackle any significant hills (read mountains) I did indeed do some long uphill slogs. Here's the GPS data

When I got it home it was pulling Volts down to 44.2 or so on the milder hills, but still pulling better than it ever did on hills, and note how steady the speed was almost to the end.

Analysis

The interesting thing was the recharge: It took 271Wh to recharge (using my 150A meter to count that), and as the battery is rated at 422Wh this means I've used up about 60% of the battery total rated capacity. Now as anyone who knows much about batteries would know, getting that last part of the energy may be hard to get to and even predictable about how far you can go, perhaps even may damage the cells if getting to it (if you don't have a good BMS). Here is why: the discharge curve.

Looking at this test discharge of Volts vs Ah working out the area under the curve (using a near approximation and I've chosen to be a bit conservative) gives me 7.11Wh per cell. So with 13S4P that gives me 13 x 4 x 7.11 = 369.72Wh of actual usable Watts. Note how quickly that last bit of voltage at 3.4V per cell just dies off.

So while my cells are 2200mAh the difference will be small (if indeed it is any different and not just "rebadged").

For all intents and purposes I'm willing to call the 271Wh I put into it (on recharge) to mean that my ride took out 271Wh Effectively 75% depth of discharge. Given also that rapid fall off at the end that last unit may be quite unpredictable (and depend on hills), its best to not be relying on that being available. Meaning I won't get much more out of it than that (as you can see how the voltage plummets towards "out of juice" and I'm walking levels.

So a real world range of 20km "flat stick" on cruise control is reasonable. The less you do stops and starts of course the better because re-establishing speed will suck more energy than just maintaining it.

Thoughts

Knowing this curve you can more accurately use your Volt meter to understand how voltage (while riding) reflects your actual remaining range. For instance, when you see certain voltages under load (you'll note that flat road cruising voltage is different to that going up a hill, because of the load). To get the chart below I used the 2A discharge measurements of the Parkside battery (because I expect its pretty close to what I've got having observed my own discharge and the battery markings) and simply altered the scale on the Volts axis by multiplying cell voltages x 13 (because I have a 13S4P pack)

So seeing anything dropping down to 45V while under load means you're getting close to the end. If you're seeing 48V you've still got at least half your power left.

Next interesting thing is that if one considers that I needed (to supply to the scooter) 271Wh to travel about 19km that works out to about 1.4kWh/100km which (as mentioned previously in the article about my dual motor variant) is stunningly good efficiency and no electric car gets anything like this. Supporting my view that for short distance frequent trips a scooter is far more the efficient transport solution for cities.


It remains to be seen if I need to give this pack any more attention, but hopefully this shows how resilient they are and how easily rebuildable they are.

For how this started please refer to this post here

Mercane 8.8Ah pack repair

This all started back at this post. However I think that this time I've nailed it, mainly because unlike last times I've identified a very significant physical factor: a rusted through connection bus strip across the postives of one parallel bundle of cells (yes, the one that was down on that last BMS test).

I found it (and as you can see it was buried beneath the paper where the BMS sat) while trying to identify which set of physical cells that wire loom (just to the right of the picture) connected to, as I'd been making my voltage measurements off that. Its hidden under the paper behind the BMS as seen in this picture:

(featuring a Reddit Approved Kitchen Utensil as a tool).

Anyway, the voltage measurements at the pack didn't marry up with what the BMS was seeing, so I dug in to see. When I peeled it back I saw a big scab of rust across the cells, which basically just crumbled away when I hit it with the vacuum cleaner.

So essentially this leaves the last three cells unconnected to the BMS and so only one cell was getting charged and supplying power.

I cleaned it up with the wire wheel on my Dremel tool ...

which showed me that I just needed to bridge that set of cells and I'll be right.

Now lacking a spot welder I pondered how to best do this, and decided that because it was the positive ends I could prepare that lone cap with some solder if I worked fast, because the top of that cap is not directly connected to the electrode. So if I worked the right way I could solder with minimal damage. The cells left and right of it I could solder onto the nickel (hah ... fucking nickel my arse) strip.

First however I gave them a balance charge with my iMax and then soldered two strands of copper ~1mm in diameter across those three cells.

I charged it till it was only pulling 0.1A and took it for a 5km ride to test it.  All went well, so over night I charged it again. This morning when I checked the pack it was at 54.6V, with 0.00Amps going in to it. I thought that was very encouraging and ideal at about 4.2V per cell (bundle).

So maiden voyage on the repaired pack was one of my standard test routes.

which is an excellent result and compares very well to what I got before I put in the new BMS and just balance charged the pack by hand (hoping that would fix the issue, but it didn't):

Comparing those two results in more specific details:

shows that the pack has a bit more pep in places but what is really significant is the voltages were way up when I got back, suggesting I'm going to have increased range (as well as I'm sure the cell balances will be better with the new BMS).

This is the voltage upon return of that trip (and an additional little 2km victory lap I did). Further as I found in my pull down and mentioned in that post, the balance charging is doing much better with the new BMS than the old one:

the blue columns are the result of a "full charge"with the old BMS, which clearly wasn't balancing anywhere near as consistently as the new one. Probably equally important is that my testing to BMS shutdown yesterday (which prompted this new pull down) gave this result:

V discharged
4.03
4.04
4.03
4.03
4.03
4.03
4.03
4.03
4.03
4.04
4.2
3.66
4.03
4.02
0.12
50.7

which:

1. shows how bloody well balanced the cells were after initial "full charge" levels are shaved off by a few km riding and
2. is what led me to to this pull down to investigate why the BMS shutdown was happening and why that cell was low.

Discussion and Conclusion

I think that this time I've got it nailed, and unless there are other cells in this condition the only reason I'll need to pull the pack down again is if the solder joints I put on need repairing (which will only happen if the solder melts because the copper heats up under power: meaning my calculations on the required diameter are wrong).

Its pretty clear that this pack has failed (dead pack walking) by catching it early I've minimised cell harm and saved money. because of improper assembly and cheaping out on materials. I'd speculate that in the Chinese Sweat Shop where this was assembled the worker involved dripped some sweat right there on that part of the bus connector and started this rust process right then and there, before the pack was even sealed. I've seen the impact of a single drop of sweat on a circuit board before (the salt in sweat just helps electrolysis and oxidation reactions go nuts). Had they used decent nickel this wouldn't have happened.

I don't believe that there are other cells with suspect (rusty) joints because I can see all those other joints and this one was the only one hidden by the paper under the BMS.

This highlights the importance of pack construction being at least as important as cell choice. For even if these were LG cells and even if said LG cells were better, it would still fail because the assembly of the pack was flawed.

I'll do some range testing and perhaps do another pull down to check again.

Basically for

• my time, and 
• 2c worth of solder and scrap copper wire

I've saved a $250 pack which I anticipate will go on to last another year (its already lasted nearly one).

I hope this is also helpful to someone else.