Saturday, 28 December 2019

scooters going fast (and why that's dangerous)

Many people seem to want to trade up their relatively safe scooter such as a Xiaomi or similar less than 500W scooter to a bigger more powerful one ... one that can keep up with the traffic. Somehow they don't want to then step up to a motorcycle ... because that's expensive ... right?

An interesting point which still surprises me is the utter denial of reality which many scooter owners on the various forums seem to have. Now I think its pretty clear from my blog that I happen to like scooters and use them a lot. However one things separates me from them: I accept that small wheels and even mild speeds do not go together.

Now there are many reasons for this but in this post I'll just go into one which should be obvious but seems to not be.  But first lets refresh the difference in wheel size and suspension between a motorcycle (which I recommend for any speeds over 30kmh) and a scooter (which I enjoy using at any speeds under 30kmh, but occasionally hit 40 in specific down hill runs)


you don't need a degree in Engineering to see the difference and even inserting a Zero 10 in that picture would barely change the facts. Not only is the motorcycle wheel huge in comparison (and this one is among the smallest) but has quad piston dual disc brakes which will allow amazing heat shedding power in comparison to the itty bitty 120mm or maybe 140mm disc on a scooter that has a front disc system. (and HINT: with telescopic fork designs don't hit the front brakes when you're about to hit an obstacle or you'll compress your suspension and make matters worse)

Next, lets look at this small stone:


not much to look at really, and could easily be obscured by other cars on the road around you or you miss it because you're looking at what a car is doing. But when you put it on the road (and you don't see it) it represents this sort of obstacle to a scooter:


Not only does that stone probably go close to requiring the full travel of the scooter suspension, not only does it have an enormous relative size, but it also puts the energy of impact (the red line) almost totally away from the useful working of the suspension (the blue line). Meaning that the suspension will not be able to do much to absorb the intial impact, only if you have penumatic tyres will you get any cushioning (and may actually pinch a tube too).

Now lets look at the motorbike wheel


not only is the rock barely significant, barely even compressing the tyre much (while it would probably result in a pinched tube on a Zero 10x or similar {and it'll be worse for smaller scooter wheels}), the shock of rolling over that is directly in line with how the telescopic forks compressallowing the suspension to exactly do what is needed.

You would not even notice this rock if your were riding at 40km on the motorcycle, but it would likely spit you off on any scooter (perhaps something with really big wheels with fat compliant tyres like the Hollyburn P5 would not).

So if after reading this you intend to keep kidding yourself that any scooter is OK at even 40kmh (people say that's slow) reflect on that experience at 80kmh (which the Zero 10x can do).

People used to call motorcycle riders "temporary Australians" ... I'd say more so for scooter riders who refuse to accept the limitations of their machines.

And I haven't even touched on stability over plain bumps or potholes or what is rake and trail yet ...

So, when doing your financial planning, ask yourself how much your injuries are worth in that economic balance.

PS: I found this well written review on the Zero 10x recently on Reddit and thought it should be shared, mainly because the fellow is well tempered and not just a High Speed Scooter Jihadi.

Friday, 27 December 2019

charging, discharging data and usage

Having now done a few explorations with my scoot I can say that the Mercane does indeed (at least in my case) come with good batteries. However what I wanted to talk about here was the interesting observations borne out of yesterdays run.

What I did and why

I decided that a nice run up my favorite (and nearby) mountain road would be in order on a quiet boxing day. I anticipated from experience that I could make it from my house all the way to the top of the mountain and back on a single charge. While I've done similar distance runs before it has not been with such a gruelling non stop slope as this. As you see its steep countryside.

The trip out to the mountain, up and down the mountain and then back home is about 20km and while its steep up there, it means that I need no power at all to get back (and because I enjoy the speed on the way down, I wouldn't really benefit from regen brakes for this or 99% of my trips). Just to be safe I used the "Economy" setting for the trip out, but satisfied when I got to the bottom I'd have enough to get home I put it back on "Power" setting. As it turns out for the part up the hill speeds were not dissimilar to my previous runs with "Power", just about 2kmh lower (which benefits power consumption).

I was satisfied at the top of the hill where it showed 48.7V, which works out to be 3.7V per cell, which is not much below the rating for the batterys "normal" level.

So on return I charged it back up and noted that it (after a minute or so to allow it to settle) was showing a battery level of 47.6V

How much of my energy did I use?

One thing for sure, is that because of the very shallow discharge curve of Lithium batteries, and slight variences in chemistry and even perhaps discharge levels within my 13S6P pack (bundles of 6 cells in Parallel in a string of 13 bundles in Series) it is hard to know the state of discharge. Like did I discharge it to half, nearly empty ... what?

I figured that the best way to determine this was to again use my 150A power monitor (featured in other articles such as here) to actually know this.

However I decided to go a step further and look to see if 1) how long the change took before the Amps going in backed off, 2) what was the exact relationship to Volts duing that constant current phase and 3) look to see how long the balancing phase took to complete.

Here is a graph of my data, you'll notice that at first I was not sampling every 10 minutes.


so basically the voltage crept up a a small amount (starting at 48.08 as soon as I plugged it in) and moving finally to 54.9 (which dropped to 54.6 shown on the bikes volt meter as soon as I unplugged the charger). Finally the charge indicator went Green just after the 4:30 interval (I happend to be there writing down the data) ... so the BMS is doing a great job IMO.

The next thing you may notice (if you read graphs not just look at the pretty picture) is that it took a little over FIVE HOURS to charge. Now this is unsurprising with the piddly little 2A charger provided. Why "piddly" well the cells in the parallel bundles are 2.2Ah, and so since there are 6 cells in a bundle that means 13.2Ah, most makers suggest that charging at 0.5C (where C is capacity) is quite ok. Thus 0.5 x 13.2 = 6.6A thus being fine and which would have charged it in 2.5 hours.

Two guesses what I'm buying next ...

Measured Values

Now what's also interesting in the data presented by the 150A (which saves me doing the maths) is the Wh supplied to the battery. This was 410Wh.

Now this is interesting because as the battery is rated to 633Wh that's actually quite a bit over half discharge. Indeed its probably the ideal discharge to take it to to maximize battery life. As previously discussed (here) discharging the battery to about 60% (regularly, not as a one off) still results in a good 600 charge cycles before the battery is degraded to any significance.


which means that the battery should last me a good couple of years (all things being equal). That's very encouraging.

What can I do with this?

Well knowing that charge and discharge of Lithium batterys is in the high 90's efficient (nearly 99%) I thought it would be interesting to see if I can (like a Tesla onboard system does) use this to estimate range. As I've already established good models of how my energy demands are on my scooter with this bicycle computational tool (my parameters) over on this blog post, and that I have access to some good data on the steepness of things (via google as well as my own measurements) I can do some estimations if my calculations are right.

So having this data I used it to feed into my GPS log of the trip and make some basic ball park figures. This is the trip data from my phone GPS app;


Note, there is a flat spot on elevation because I got a phone call mid test and stopped to answer it. Then using that simulator (mentioned) I was able to roughly (ball park) divide the trip power demands up thus:


into different power level demands based on plugging that data for slope and speed into that simulator. Making some simple assumptions and measuring scale off the graph I got:

60 min = 532 pixels
1 min = 9pixels

High power period @650W = 148px + 90px = 238 = 26min = 281Wh
Standard power period @300W = 72px + 84 px = 156px = 17min = 85Wh
Only 43min in the hour was powered (because "gravity")
281+85 = 366Wh

Which when you consider that as reported above that charging required 410Wh that's pretty darn accurate.

Next, when you factor in the distance covered (as a challenging drive condition) I used 410Wh to cover 20.83km. Alternatively this works out to be 1.96kWh / 100km ... This is something we can now use to compare to many EV's such as (say) a Nissan Leaf which is something over 13kWh/100km

That's pretty darn good.

Outcomes?

this serves to verify a few things to me:

  1. the battery pack rating is good for real world expectation (I don't think I'll do a "till fail" test, because walking in the heat is not attractive)
  2. the battery pack is good quality
  3. my empirical observation derived Coefficient of Rolling Resistance (Crr) seems to hold well in many circumstances
Pretty darn good I'd say


Wednesday, 25 December 2019

When is it charged?

Discussion on a forum yielded the idea that charging can continue (at least on some systems) after the charging lamp changes from Red to Green. This blog post serves to show that it can and probably does.



As it happens I have an inline meter which measures this sort of thing (as well as accumulates a bit of data such as peaks and averages) and is sensitive to 0.01Amps over quite a voltage range. I bought it for working with Solar charging systems (and its appeared in a few videos before). I'd adapted it to plug inline with my Mercane charger and allow me to monitor the charge.

Now my Mercane Single is pretty cut and dried, and does not charge beyond what works out to be 52.2V at the battery (after the charger is removed) and the Battery Management System (BMS) essentially truncates charging while still some amps are going into it. I'm unclear if this is a "whooo that's great" design or and accident, or even a fault?  This behaviour is a fault documented and explored here) As my range has not been effected since I purchased it (some hundreds of charges later) I can only assume that its not a bad thing. (<< its the sign of a bad thing).



However it may (eventually) result in the battery pack getting out of balance (I just don't know because it depends on how charging systems vary) with over time some bundles of cells not getting as high as others or being dragged down too low (and reducing my range).

My Mercane Dual motor however must have a different BMS as I've found (as a result of that discussion) that investigating my Dual motor (which a 50% higher Wh battery) behaves differently. It charges quite solidly at about 2 Amps, then towards the end falls off. Like this:



You can see a small taper off in voltage and it still draws an amount until it eventually falls to 0.00V

So lets look at the phases of charging (meaning what happens over time) for a normal lithium cell. Its divided into constant current (where the cell soaks up all the amps its given) and then a drop in current signals that the battery is filling up (as the cell starts to fill up like a baby not wanting more) and that amps going into the battery represents the charging (which it does see here).


You can see that there are only small changes in V note my red annotation lines up until the battery starts to slow down accepting more electrons (and Charge current drops). Yet it takes nearly another 2 hours before the battery is at 100% capacity. Its at this time that the BMS starts distributing incoming power to the other cells.

Having some understanding about how many BMS work, this is consistent with the "distribution phase" where power is distributed to the lower cells (often from adjacent cells also being topped up by the BMS) until (*I assume) the cells are all at 4.2V or the BMS gives up and declares there is not enough current moving and the cells are as balanced as they're going to get.

In the video (segment) of my charging below you can see the moment when the light went to green, and then the 150A reported a drop in amps being drawn to under 0.3A


Which shows that it may not actually be finished charging when the light has gone green, as current is still being drawn for some time. Without a meter (like this one) there is really no way to know (unless your scooter has some fancy firmware that monitors charge) what your batterys behaviour is.

I believe that this implies that the green light on the charger is switched from Red to Green when the amps drawn from the charger falls below a threshold, however charging may still be taking place.

So for those who are "worried" about the battery being "killed" on the charger, I recommend strongly that you consider giving it a full on the charger overnight charge at least now and then (perhaps every second charge.

I think its silly to worry about this, because its only the leaving of the battery at over 4.2V for significant durations that causes any (minor) harm to the battery. I'd say that mine only stays at 4.2V for the small amount of time between full charge and usage commencement ... may as well go out for a ride eh?



Sunday, 22 December 2019

Bicycle VS eScooter (and conjecturing an eBike)

I went out yesterday morning around one of my regular roads on the bicycle (which is a basic MTB {Giant Roam}) and decided to just "pace" around, not breaking any records, not dawdling. I got this:


You can see the ups and downs in speed corresponding to small hills and as you can see its only mildy hilly.

So this morning I took the scooter on the same path and got this


Notice how much more even the speeds are? It's far more constant (thanks also to the cruise control, which I would never have a scooter without...) and you see almost no deviations down in speed due to up hills and about the same maximum downhill speeds, although the bicycle did make better advantage on down hill with longer durations and a higher peaks speed (probably influenced as much by rolling resistance {scooter worse}, wind resistance {about equal} and my speed limiter being 24kmh on the scooter).

So this suggests that if I was interested in commuting and my trip leg distance was higher than 10km that I'd be better off with an eBike than a scooter because basically on the bicycle I was the only power and on the scooter I put no power into it at all. I'd say that I could maintain a constant 30kmh on the milder hills, still reach 44 on the down hills and bring my average speed up significantly probably 10kmh over the scooter and all that with probably only 500W needed (some times).

Indeed my favourite bike calculator suggests I'd probably only need to be pulling 200W from the motors to maintain 30kmh (given what I was already doing) and that even up steeper than the steepest grades I'd only need another 200W on the way up.

This lends support to why eBikes get by with less battery and manage longer distances with that.

PS: I didn't think this deserved a separate post,  but just did another quick (shorter) trip and got this (more or less just into the shops in town and back without stopping).

Bicycle



Scooter

Note: there seems to have been a GPS issue which appears on the map where I seemed to jump across country so the distances seem off, but the speeds and duration clarify things still.

  • higher down hill speeds on the bicycle
  • more slowing on the quite minor hills (scooter was clearly well within its power and torque for max cruising speed on them)
  • slightly quicker on the scooter
My observations and comments are that the scooter can be walked into the shops (which I do) but the bicycle (and of course an eBike) couldn't. I didn't get the slightest bit sweaty (and it was early morning as you can see and temps are still low, recalling that its summer in Australia now). The scooter is very quick and convenient for such small trips, however one has to constantly survey the road for bumps roughness which on the bicycle would be unneeded (well obviously huge potholes) because my MTB has 700 wheels and a basic entry level telescopic fork making it smoother than any 8" wheel (even with suspension) ever could be.

If you haven't read this I recommend it, allow me to quote the relevant portions.


Smaller Electric Scooter Tires Have More Problems with Obstacles

Most electric scooters have tires measuring 6-8 inches in diameter. This is far smaller than the average bicycle tire of 25 inches. When encountering an obstacle the smaller tire (scooter) has a much harder time going over it.
The chart below shows the additional force needed by a scooter to overcome a step compared to a bicycle.  This graph was plotted assuming a 26″ bike wheel and 8″ scooter wheel.
Even for a 1 inch bump in the road, the scooter will need 50% more force to roll over it — and you’ll feel a much larger jolt.  An unexpected pothole is more likely to turn you into an acrobat with the smaller scooter tire.
And I hope that the following diagram makes totally clear why that energy rating is so, as while both wheels have to raise up 1 inch, the impact to forward momentum on the bicycle is quite different (look at where the obstacle is relative to the center of the wheel, most of the wheel is already past it on the bicycle, allowing the rest to roll over it, but not on the scooter.

Happy Scooting

Friday, 20 December 2019

Merry Christmas (and a Happy New Year too)

To everyone who reads my blog, here is wishing you a Merry Christmas


and my fervent hope for a Happy New Year

Thursday, 19 December 2019

Scooters in Retrospective (where are we going)

... and indeed where am I going?

Back in 2009 I worked in an office which was a significant walk from the train station, and as it happened largely down hill (mostly gentle, mostly). I decided to buy a kick scooter to get from home to station and station to office. I wanted something with decent diameter wheels (200mm) and got this little fella for €50


it served me well and I used it for quite some time with no issues (even solved the wet and grit throw-up at the back with some duct tape)

Then just this year, I started back at an  office where I wanted to "shorten the walk" and a scooter immediately came to mind, I bought this little fella which was more or less identical and for about the same money AU$70.


but perhaps has less heavy duty "everything" because the bearings collapsed after less than a week of my usual scooter treatment. Certainly the spokes look less substantial and the PU "tyre" feels harder than I recall the other being.

Anyway, I promptly replaced the bearings, but (due to a knee ligament injury on a trampoline (don't ask)) began considering something I didn't have to kick and soon settled on the Mercane 500W single motor (although seriously considered the dual motor 1000W version, which I subsequently ended up buying...) pictured here beside my little kick scooter.


Quite a difference in so many ways (including price).

Much nicer tyres, which are a composite of foam and a pliant grippy rubber, and some suspension too to help reduce the impacts to critcal things like bearings, axles (which are hollow on electric scooters with hub motors) and perhaps even you.

I notice now that people are King Wang'ing on about "comfort" (as if these things were like luxury cars). Probably these people have never ridden a kick scooter (or have forgotten what it feels like with actually solid tyres).

I had to move my (sadly now disused) little black kick scooter and thought how small it looked. Picking it up I nearly laughed at how light it is. Quite the contrast in relation to my 1000W dual motor Mercane.


So while my little kick scoot would comfortably fit into an overhead rack on an intercity train my dual motor Mercane would certainly not (and something may well get broken were I to try shoving it up there).

Recently I've started serious investigation into buying a Zero 10x ... which is even heavier than any of these scooters. It goes like this:

  • Evo = 5kg ($60)
  • Mercane 500W = 19kg ($1000)
  • Mercane 1000W = 23kg ($1400)
  • Zero 10x = 36kg (for the 24Ah model) ($2700)
*(prices in Australian Dollars)

It was not that long ago at all when electric scooters were like this:

*(wikipedia image)

So, what else can I do with $2700 (or more), well actually I could buy a pretty decent 500cc motorcyle with low kilometers on it for less than the price of the Zero, like say one of these:



Which will do many thousands of kilometers, last for many years (my Yamaha is already 12 years old with 125,000km on it) and be able to take you out all day, tour, commute and carry a friend too.

Better yet there is another sort of safety in motorcycles; rego and insurance (which the kiddies will squeal and shriek about), which is mandatory on motorcycles and cars. While this may seem like an "unnecessary expense", it will mean that if you're in some sort of accident (it won't happen to you right, err, unless you're one of the kiddies justifying a full face MTB helmet, elbow pads, body armour and other cos play wankery, then its inevitable) then you'll probably find that the $200 per year you paid in insurance is cheaper than forking out for that multi-thousand dollar car door repair (which you'll be blamed for because the cars insurance company will sniff out you are not in a good position to defend that) or worse yet, you hurt a person and be liable for hundreds of thousands for personal injury.

Doesn't sound cheap to me (and is the reason we have laws around vehicles to prevent cheap scates from leaving people at a loss) ...

All this has me wondering where I'm going with this and if I'm trying to make the Electric Scoot into something more like a motorcycle, and indeed if it actually even is?

Myself I think the sweet spot is somewhere around the zone between Xiaomi 365 and my Mercane.

Dunno ... I'll keep you posted on what I choose to do.

PS: I found this review of a Zero 10x on Reddit, this guy seems to think like me.

Sunday, 15 December 2019

two types of scooter users

It seems that in todays polarised world there can only be the extreme users, however I'd like to put forward the case for Electric Scooters as being a practical daily transport which you can rely upon to quickly get you to places which while you could walk you'd be nearly tempted to take a car.

Case in Point

My local shops, its not far (about a kilometer) which if I walked there and back would be just under half an hour. Its mainly flat, so no major impediment there, but when its hot (as Australia can be)


the thought of walking up to the shops in high UV as well as high heat is of less appeal than you might think.

In contrast a quick scoot there and back (probably in not much different time to starting the car, backing it out and so on) with the air flowing past cooling one down a little (sweating is cooling) seems down right appealing.

Its a role like this that a lighter weight 500W single motor scooter (not a beast with 3,500W) makes for a simple and pleasant trip. I did just that this morning and thought I'd share with you the results and perhaps use it to discuss some aspects. This is my trip out to the shops


and you can see its pretty flat, took just over 2 minutes (including fumbling around turning the GPS off) and despite what the GPS thinks (I suspect accuracy issues with it just being started up) there wasn't a big climb at the start. Important stuff is average speed moving and average speed ... so more or less I spent most of my time at 24kmh, that's probably as fast as most people would call a brisk cycle on a bicycle (but without the sweating). Importantly I forgot to start the GPS on the way out, I was 500 meters from home

The way back was similar:


which reflects that the slight long down hill back here does makes it that little faster. Note I've selected distance there not duration because not moving does not show distance and looks weird on the duration view.

Discussion

On various forums you'll get the spakko kiddies and adventure adrenaline junkies telling you you need a 3500W monster and that scooters are safe, however with those higher speed higher power monsters falling off (going fast) can result in stuff like this:


Which brings me to why I like my Mercane Single motor 500W scooter ... its easy to ride, stable and feels safe.

Sure I could fall off it too and hurt myself as bad, hell I could slip in the supermarket too ... but the point of this post is to say this:

Not everyone needs or wants a speed demon, they might just want to get to work and get to the shops. 

Impact forces increase with a square of the speed, so while the time taken to get to the shops may be 40 seconds more, its still much faster than walking and on a scooter you're pretty much as exposed as a pedestrian ...

Best Wishes and Happy Scooting

Monday, 9 December 2019

brake mods on the Mercane (or Don Quixote does brakes)

upfront

Myself I'm not interested in this mod, I'm more the Sancho Panza and fundamentally the brakes on the Mercane are quite sufficient, have good lever feel and operate nicely (if you spend a little time tuning them). If you think they don't for then this most likely means either:

  • you have a faulty caliper (so just replace it) or 
  • it needs adjustment (and I've got descriptions of that here). 

Now pardon me being blunt, but if you are of such meagre mechanical aptitude (and unwilling to learn) then I think you should know right now that you won't be able to fit the (somehow) popular X TECH caliper ... because really that's going to require far far more work than just spending a bit of time unbolting the existing caliper, exploring it (and seeing how it works) then adjusting it.

Lastly there is a lot of misconception by people who just don't seem to have the faintest clue about how brakes work. The standard Mercane brake has two pads one on each side of the caliper but only one piston which pushes in. It relies on the flexing of the (its only 2mm for gods sake) disc to operate and push against the inside pad. So adjustment requires that inside pad to be kept in close (almost touching) to the disc; because it doesn't move.

Now naturally there are those who just like to mod for the challenge ... I used to do that, and for those folks, this is here.

The nuts and bolts

This is the XTECH beside the existing caliper ...



its should be immediately apparent that its bigger (and not clear here, but will be soon) its a lot fatter too. Now, if you're still enthusiastic you'll notice that there are two variants, a Front and a Back, they are different only in the supplied bracket (I bought the front)...


because it looked lower to the mounts and that looked like what I'd need. Take a moment to compare the center of the pistion and its relationship to the mounts with the center of the OEM part and its mounts ... the black one is too high and back ... but that's not where the problems end.

Next lets have a look at a quick video (sorry is vertical, but its easier to compare them one above the other like this).

So assuming you watched that, what it results in is that the extra bulk comes VERY close to the rim


less than millimeters in fact...



and as you can see also, I still don't have it in a place on the mounts.


Which sort of mirrors the configurations of the posts on Reddit where people have tried to mount this caliper ... always with odd angles and very small clearances (meaning rim or caliper damage is likely).

Now part of the problem is also that the mounting bracket will need to be shaved a few millimeters to allow that caliper to move further to the outside, which may allow it to clear the rim, but that's going to mean the disc will need to move out too (as here its actually seated on the disc).

Here I've bolted the caliper bracket onto the swingarm mount points and you can see how little clearance there is between this and the disc...


So not enough to move that caliper out without shaving that bracket. There is room to shave 2 or so mm off the outside of the bracket without compromising strength though if you're keen (and reports mentioned below suggest other users needed to do that too).

Of course to move that out, you'd also have to move out the disc, which would mean packing that out with (say) some 2mm washers. To be able to do that you may find its easier to take the wheel off ... but I think it can be done without removal.

Lastly you may have noticed that the bracket is not "even" or regular in shape:


with one side being higher than the other ... which means you can have some room for altering which tilt works best for the caliper by mounting it one way:



or the other



So if after this you've seen enough to energize yourself into getting one, please leave a comment on how you got it mounted and (better yet) what your long term finding of it was in terms of:

  • pad life
  • going spongey (can't be bled as its sealed)
  • adjustment as the pads wear (should just be take up on the threaded adjuster)
I am in no rush to do mine, but as I have also bought some spare discs may make a project to add front brakes (which I'm also in no rush to do because I don't think front brakes will be a "good idea" on the scooter.

Lastly some reddit posts:

Bottom line:
ultimately I could get this going if I was so inclined ... but for what? My brakes work fine with less time spent than modifying the brackets and I have not had to weaken anything or add more bolts into the mix.

A final point as yet un-mentioned is how much much heavier these calipers are ... compared to either the standard Mercane or the hydraulic ones on my MTB


because there has to be both master and slave cylinder built into one (just for starters).

HTH