Saturday, 21 May 2011

Do electric scooters dream of being petrol powered?

Its starting to get fashionable to talk about Electric Cars again. The other day I was in at the local scooter shop getting a tyre sorted out for my Yamaha T-Max scooter (and pondering a purchase of a new 50cc scoot for my wife) when I spotted this electric scooter. So (being an engineering sort of fella) it is exactly in my nature to use this situation to mull over the whole thing (and present it to people who may not have thought about it).

I have been interested in the concept of an electric scooter for a while now but had not really done much research on the topic.

So since it was right in front of me I thought I'd ask some questions, take some pictures and write about it here.

I will say from the start that I like the idea of an electric scooter for city work more than petrol ones for the simple fact that most scooters are 2 strokes, stink and pollute something fierce.

India made a great move when they legislated their nasty "auto" taxis to use CNG rather than the regular 2 stroke ones of the past. Emissions fell and everyone is healthier and happier for it.

Its true that electric engines will need power from the regular power stations, which are in the main coal fired (at least in Australia). However at the very least we move this pollution to a single more efficient generation source (while introducing an number of other inefficiencies in the middle) which can be more controlled and monitored.

Before dribbling on about that too much I thought I'd toss in a comment about the rear drive on the scooter. A brush-less 48Volt 4000Watt hub mounted motor: man that means it can suck 83 amps!! wow

Which makes for some interesting observations about the changes in engineering of the swingarm and frame (because the forces are different now).

The motor can suck up to 4000 watts of energy out of your buttery but of course will only pull as much as is needed for keeping a constant speed when cruising along at a steady speed (say 50Kmh). This is of course exactly like a petrol powered motor, which sucks fuel faster when pulling power than does when cursing along. Interestingly both produce about 4000 Watts of energy (yes, 49cc scooter or electric scooter give you the same power to take off) which should come as no surprise because thats regulated by government.

[aside: to put this sort of tiddly power delivery into perspective, a "vanilla" motorcycle like a Suzuik GS500 has a motor that will deliver at least 38,000 Watts and a timid car like a Ford KA which squirts out something like 48,000 Watts of power. So as things go the electric scooter is not pushing the engineering envelope here]

Putting energy in:

People somehow think of petrol as fuel but electricity as energy, I blame our schools for creating this schizophrenic view of reality. The reality is that fuel (petrol, gas) is energy in liquid form. We release that energy by burning it. An Engine turns that energy release into movement. An electric scooter doesn't have an engine (somethhing else has to generate the power) it only has a motor.

The electric scooter stores energy in rechargeable batterys and gets the energy to recharge the battery from your wall socket using something like this:

This little device (which is about the size of a small shoe box) is the charger for the scooter.

To charge your scooter up you have to plug this in to the wall power and into the bike. You can not really run a long extension lead to of from it, or you will loose power so we meet:

Problem #1 - where can I recharge

If you have your own house and garage you can probably charge it up in your garage, but if you live in an apartment its quite unlikely you have power available where you park your scooter. So you'll need to find a place where you can park it and recharge it: which takes 4 hours. In contrast the regular scooter recharges with fuel at the local servo and takes about 5 minutes to fill and pay for.

So, with fuel being (at the time of writing) about $1.5 a Liter a petrol powered scooter takes about 5L in the tank and will set you back about $7.50 to fill up from dead empty. Its unlikely you'll run it dry, so you'll probably put in 3L at a time and walk into the servo to pay your $4 bill while grinning at the people who fill up their cars and are paying something like $60 for that.

So what does it cost to "fill up" the Electric scooter?

Well of course electricity costs, in my area right now power you pull out of the wall costs you about 19c per 1000 watts per hour. Its normally written as kWh which seems to confuse people who often profess to not understand their power bill. Its not all that had to get. Essentially if you plug in and turn on something which uses 1000W (or a kilo watt or 1kW) and leave it turned on for an hour it cost you 19c.

So how does this apply to the Electric scooter?

Looking at the charger we see that it supplies about 900Watts to the battery. I'm certain it is not 100% efficient so lets give it some grace and assume that its going to pull out 1000Watts of power from your power point in your home (or wherever its plugged into).

So (based on the above rate for power) a 4 hour charge will cost you something less than a dollar, 78c our thereabouts.

According to the information I have on the scooter (which you can verify here) For this princely sum you get to travel 90Km (only under particular conditions).

That is quite attractive. Sounds like its quite positive when reading the basics. So lets plumb into the ownership and do a little bit of thinking:

cost comparison

Ok, so 80 cents gets you 90Km on the scooter, but it will of course vary on how you ride and in what conditions. 90Km is of course also the maximum distance, so if you commute across town 25Km you'll not quite get two trips into the one charge (as 50 + 50 will put you out of battery) and you can't stop and top up on the way like you can with a petrol bike. The actual distance you will get may be less depending on factors like:
  • hills
  • number of traffic lights
  • how heavy you are on the throttle on take off (kiss bye bye to fast take offs)
This means that (unless you want to be pushing it home) you'll have to top up every day (fine if you park in a garage in your home, annoying if you have a flat).

So you may be plugging in again and paying that 80c every day instead of the potential discussed by the maker and seller of the bikes.So it may become more like 80c for that 50K round trip.

If you were to consider a petrol scooter (as a comparison) such as the Honda Scoopy, assuming you get something like 3l / 100Km (and some have suggested you can get 1.4L/100Km) you will pay $4.50 for 100Km or $2.25 for that 50Km round trip. Clearly the Electric scooter is in the lead here.

Yet, thats a worst case scenario too, as if do you get 1.5L/100km (which is actually likely) then that'll be more like $1.12 for the trip. Starting to look less like a clear winner as its much the same fuel cost as the 80c for the scooter isn't it?

Of course with the petrol version you have the flexibility that you KNOW how much is in your fuel tank, battery charge level is not as accurate and will depend on how cold it is. You can top up your fuel in minutes but need hours (back home where your charger is) to top up the electric scooter.

So this begs the question of how much is the convenience that petrol provides worth to you?


Back on the costs: an acquaintance of mine who has an electric bicycle (less power so smaller and cheaper battery) recently changed battery from the standard one. How much did that cost? Well think in numbers closer to $1000 than $500 and you're on the path.

So unless you're after a battery for one of those tiddly little electric bicycles (with all that implies) you're thinking big money for a battery for this scooter. This starts to lead into the next problem identified for the Electric Scooter and that is:

Problem #2 real operation costs:

Anyone who has owned a vehicle knows that there is inevitably more cost than just putting fuel into it. For a start there is repairs and depreciation. So, thinking about the above battery example, how long will your rechargeable battery last and what will it cost?

Well its only covered by 1 year warranty. So assuming you use the battery optimally (charge and discharge according to the makers ideals) you'll certainly get a year out of it, perhaps two. But what if you don't use it optimally and it fails outside of the warranty? Are you going to learn to do that or is convenience going to get in the way?

Consider that at the fuel prices of $1.50 /Liter (and before you say that may rise over 2 years ask yourself if power won't) you will get 20,000Km of travel from $450 of petrol.(*calculated at the worst fuel economy)

So using our example again: if you travel 25Km each way to work, thats 50Km per day = 400 days of travel.

Now, if that battery needs replacement (and ask anyone in Remote Control Helicopters how often that happens) then you'll be up for something between $500 and $1000 or perhaps more.

Yes, that's right ... your entire year of fuel bill will blown on a battery replacement. Which means in another way of thinking about it, that you are actually costing yourself an extra 80c a trip just for the hell of it when using an electric scooter.(not to mention all the issues like where do you charge it if you live in a high rise apartment without a garage)

Ok, but we're CO2 free right? That's got to be worth something hasn't it? Well, let me introduce you to ...

Problem #3 - CO2 generation

Its hard to get figures but it seems that (for coal powered stations) about 900g of CO2 is released for every kW of electricity. So given that the Electric Scooter will need upto 4kW from the wall every day (using the above situational example) it will thus end up generating about 3.6Kg of C02. Of course you could run it to the edge and charge every second day (and push it home occasionally) halving that figure, but that's up to you (and pushing is good exersize).

In comparison burning petrol will release about 625g of C02 for every Liter burnt, but if assuming you burn 1.5 Liters for your 50Km (that's 3L / 100Km) trip, at about a 1Kg of C02 (Note: these calculations are based on figures for C02 in petrol from here). If you get better fuel economy then you'll generate less.

so yep ... the petrol version generates less CO2 as well.

Its not looking good to me at this point ...


Naturally at this point someone will make the observation that Electric Scooters are at the beginning of their evolution and that petrol engines benefit from decades of development. Well if you have never gone to school or been taught to do any reading you may believe that line.

Let me assure you that both are quite developed technologies.

Petrol motors are actually not significantly advanced compared to 40 years ago (only we've worked on mainly curbing their emissions of other stuff) when you could buy a 70cc Honda Cub (lovely scooter) which used almost exactly the same amount of petrol as the bikes do today.

Then there is the Brushless DC motors used in the scooters, these have been in commercial use since 1886. So its mainly the battery technology which is changed to make storage more compact and perhaps controller circuits to make the motors more flexible. The basic physics of power required to move something hasn't changed between the motor types.

This does not effect the cost and pollution aspects of this calculation (except to say that modern batteries may be a more significant pollution issue than lead acid batterys).

Problem #4 - capital costs

Right now (if you look closely at the first picture) you'll see that we have been considering an electric scooter equivalent to a 50cc scooter costs about $4250, while a 4 stroke *(more powerful, much cleaner burning less polluting than 2 50cc stroke) Honda Scoopy will cost you about $2500

Yes, you did read that right, you'll pay nearly double for a less powerful electric scooter which will likely produce as much C02 (if that's of interest to you) and certainly more other significant toxic waste (read up on the disposal of Li batteries) than will result in the choice of a modern 4 stroke petrol powered scooter (compared to 2 stroke motors which are quite dirty creatures).

An excellent document prepared for the Victorian Competition and Efficiency Commission (here) suggests that scooters are more more effective people movers than cars are in cities. No surprise there...

To make the case even more for scooters, according to that same report: "A 2000 report (Motorcycle Transport, Powered Two Wheelers in Victoria) by transport researcher, Professor Marcus Wigan, found that motorcycle riders were the only transport mode to indicate no time delays as part of a trip."

There are articles available written to counterpoint this blog post (such as this one) where they suggest that Electric bikes are better than petrol powered ones. Its worth noting that these are largely written by people who actually sell the electric alternative (but not the electricity).

Its interesting to note that in the post I cited above the author makes the comparison between a electric bicycle and a postie bike (Honda CT110). The CT110 is a work horse, it'll carry another 40kg of mail and still accelerate and travel at 60Kmh if you desire, but the author makes a disingenuous comparison with an electric bicycle (which only carries you and you have to pedal too) comes out on top (when he ignores the battery issue). Yet the bicycle has a motor which wouldn't have enough power to pull the skin of a custard when compared to a postie bike ... gosh, bet that'll be popular on the farm!

But what about Solar charging? That would be CO2 free...

Well that's a good point (especially if you ignore the production of panels). If you were to get a 1.5 kW system it would likely produce enough energy on a good day to charge your scooter (if you left it at home) within 5 hours (you don't get 1.5kW all the time out of them, ask someone who owns one). So for the additional investment of $2500 (around about and you won't be back feeding the grid while your charging) you can be comfortable in the knowledge that you won't pay that extra 80c a day (but you'll still pay the other costs)

Woo hoo

But that's then an investment:
  • $4200 for the scooter, and
  • $2500 for the solar charger system (no rebate on that one)
taking your investment to $6700 for a system which needs you to leave the bike home duringthe day for charging ... sounds great to you too?

Depreciation bell ringing yet?

So in summary:

It seems like the following to me
  • I will save a little per trip (a best case of about 80c for a 50Km trip vs $1.25)
  • but I pay double to purchase ($4200 vs $2500)
  • unknown depreciation losses (but its fair to say you can't loose more than $2500 on the petrol scooter)
  • pay more for ongoing operational costs (the battery will die, motors often last ages)
  • actually create more pollution in almost every way by using an electric scooter over a petrol one.
  • You have to be able to park it where you can charge it (in a secure place or risk getting your charger stolen)
  • if your running low in power on the way home you can not just stop in to a servo to top up.
Why are you buying the scooter? Economy? Environmentally friendly?

The bottom line is if you want to be really environmentally friendly, go get a 110cc 4 stroke scooter stop driving your car and help save the worlds atmosphere and resources.


Arg said...

There are about 10 biased inaccuracies in this post, every single one of them against the EV.

You seem to be in Australia? Buy green power and all the coal power station argument is gone.

It is reasonable to assume a battery life of 7 to 10 years. Not many scooters are still going at that age anyway so effectively remove battery replacement from the sums.

The battery charger will not consume 80 cents of electricity every time you charge it. If you only used a half of the battery then the recharge will cost 40c. And while I'm at it, it's wrong to assume the 4-hour recharge is at max charging rate of 900W, these are smart chargers and only replace the electricity taken out of the battery plus about ten per cent for inefficiency.

A more realistic test showed an owner used his escooter for a month, went 700km and consumed 40kWh of electricity. Assuming 45kWh of mains power needed to recharge using the battery charger, that is $8.50 for 700km, say $1.20 per 100km, equal to a petrol consumption of 0.75 litres per 100km.

The 4kW emotor can probably produce about 16kW for short bursts, try that on your 49cc scoot.

I guess your knowledge of the electric drivetrain is deficient at every turn, which is fine, but a little more humility might be appropriate on this issue.

One thing I agree on completely though: the up-front purchase price of an EV is higher than an ICE, partly due to volume economics and partly due to battery prices which are on a downward curve (per kWH per recharge) as research continues. Parity one day, but not yet.

obakesan said...

Hi Arg

>There are about 10 biased inaccuracies in this post, every
>single one of them against the EV.

interesting claim, inaccuracies I will accept, claims of biased is just you being unhappy with what I write. I am probably greener than you my friend. But I desire reality and while I work towards it in my own life I will not wreak havoc upon the earth for the fantasy of pretending to have
it now

>It is reasonable to assume a battery life of 7 to 10 years.
>Not many scooters are still going at that age anyway so
>effectively remove battery replacement from the sums.

its reasonable to assume they should, but not what I hear in the real world. Can you please cite some figures?

I can say personally with RC vehicles I do not see such life, and my discussions with people with electric bikes do not seem to be better than 2 years.

>The battery charger will not consume 80 cents of
> electricity every time you charge it. If you only used
>a half of the battery then the recharge will cost 40c.

that's how it should be (and is with a liquid fuel) but it is not how it is with batteries. I have worked for many years in electronics and started working with rechargable devices in the 1980's and continue to do so.

please go look up the figures, or better yet get a meter and start observing this yourself.

>And while I'm at
>it, it's wrong to assume the 4-hour recharge is at max
>charging rate of 900W, these are smart chargers and only
>replace the electricity taken out of the battery plus about
>ten per cent for inefficiency.

again that is a simplification as the charging is not 5W out and 5W in ... as you assume that it is. The efficiency may be more when cycling deeply but not at shallow cycles. If you had any engineering background you'd know that.

>A more realistic test showed an owner used his escooter for
>a month, went 700km and consumed 40kWh of electricity.
>Assuming 45kWh of mains power needed to recharge using the
>battery charger, that is $8.50 for 700km, say $1.20 per
>100km, equal to a petrol consumption of 0.75 litres per

ok, well granted that that test is valid 0.75L it is still not far from what I quoted (1.7L / 100Kmh) AND as you observe and agree with the purchas prices of the EV is FAR FAR higher so the amount of fuel used in some years of operation of a good clean EURO 3 rated scooter

obakesan said...

>The 4kW emotor can probably produce about 16kW for short
>bursts, try that on your 49cc scoot.

well 1) that's illegal in most places (as the power rating is part of the licencing) 2) that will shorten your motor life (won't that be expensive?) 3) power comes from somewhere so your battery system will be slurped faster leaving you with an unpredictable shorter amount travel.

Then, if we are going to be wanting more power a 125cc scoot will produce even more power and in general use consume nearly as little fuel as the 50cc does while being as efficient. Pointless to argue that more power is more power or that modded stuff can be more powerful.

my 500cc scooter consumes on average 4.1L/100Km on the highway doing 100Km/H

end wall pissing...

>I guess your knowledge of the electric drivetrain is
>deficient at every turn

again you assume wrongly ... and so some humility on your part would be due too. As it happens it seems that you don't know much about engineering based on your claims ... I have been an electronics technician and have a diploam in Electrical Engineering. and you have?

>One thing I agree on completely though: the up-front
>purchase price of an EV is higher than an ICE, partly due

>continues. Parity one day, but not yet.

perhaps one day, but perhaps it would surprise you that such a battery with such a capacity for charge would also allow such a capacity for discharge and would be quite dangerous. Just as dangerous as a similarly rated explosive.

Finally I counted you address 5 issues, counting your false assumption about my limitations of electric drive train. Its lovely you claim 10 but there were only a few points you could take issue with not 10

I'm not trying to debate with you because you are clearly someone with strongly held opinions and facts or discussion are uniportant to you. I doubt that you would alter your point of view despite the amount of evidence because you "belive" that you are right. Believe in your righteousness is what drives religion and probably most of humanity.

Thus we are stuck in the situation we are in the modern world. Science is still subjugated to religion.

Cameron Murray said...


I have started to read your blog a number of times but always seem to get distracted.

First comment - this post is GOLD! Also, ones like your floor heating system (solar powered to self regulate and <$200 cost – genius) are not only creative, but useful for readers. I think I could learn a thing or two.

Would you mind if I cross posted this on my blog today (soon)?

I have some time to keep reading, so expect more comments. It also seems our interests overlap quite a deal, so I will link here from my blog as well.

Take care.


Daniel said...

Wow the fact they emit more CO2 was a shock to me!

obakesan said...

sort of gave me a fright too ... I double checked my figures and would be happy for anyone to refute them and show I'm wrong and where I went wrong in my calcs.

I'm not perfect, so genuine corrections will be acknowledged and published

obakesan said...

Thanks to Paul for calling me out on my units:

The units are incorrectly written though:
kilowatt = kW (not Kw)
kilowatt-hour = kWh (not Kw/H) it's not 'per hour'

this has been now cleaned up

Tim Little said...

Some of the least expensive or cheap electric scooter you will find will run on electricity and will never require oil or gas

obakesan said...

Tim Little leaves a nice bit of spam on my site, which I thought I would entertain.

Reading that review we see really fantastic stuff, like pneumatic tyres ... wow ... only available since 1887 and gracing every bicycle made this century, they list that as a feature.

gosh ...

Best comment I've had yet was that if you want to be effective then use a electric assist bicycle as the bicycle is the most efficient transport system yet invented.

These have lower weight, lower speeds and lower power needs. They actually work well.

Or you could just stop being a slob and pedal