Monday, August 22, 2011

Electric v petrol scooter

I've been reading some great posts recently at Chris Eastwood's blog in my view... . Below is a full post comparing the merits of electric and petrol scooters in a detail rarely seen.

But first a few quotes from Chris that might get you interested in some of the ideas floating around on his blog.

By having an increasingly itinerant population is it any wonder that no one gives a rats arse that your home is being degraded? (here)

I recall a conversation with 2 educators on Fraser Island ... that the last thing you want to do is encourage more people to come to national parks, even if it does somehow liberate more funding from the government it won't pay for the extra damage caused by the extra bogans. (here)

The full electric scooter post is below, and the original link here. Chris finds that the electric scooter produces more greenhouse gas emissions than the petrol version. Please keep in mind the rebound effect, since the electric scooter is so much more expensive (the owner can’t spend that money on other goods).

Over to Chris.

It’s starting to get fashionable to talk about Electric Cars again. The other day I was in at the local scooter shop the other day getting a tyre sorted out for my Yamaha T-Max scooter (and pondering 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 a 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 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 and 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.

Motors turn that energy release into movement. The electric bike stores energy in rechargeable batteries 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 cannot really run a long extension lead to it or you will lose 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. It’s 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. It’s normally written as Kw/H which seems to confuse people who often profess to not understand their power bill. It’s 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 let’s give it some grace and assume that it’s 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 let’s 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 again you'll be plugging in and paying that 80c every day instead of the potential discussed by the maker and seller of the bikes.

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 that 100Km or $2.25 per day. That’s a worst case scenario too, as if you get 1.5L/100km (which is actually likely) then that'll be more like $1.12 for the trip.

Starting to look like much the same running 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) recently changed battery from the standard one. How much? 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. This starts to lead into the next problem identified for the Electric Scooter and that is:

Problem #2 real operation costs:

Thinking about the above battery example, how long will your rechargeable battery last? 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 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.

If you travel 25Km each way to work, thats 50Km per day = 400 days of travel.

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.

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 about 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 exercise).

In comparison burning petrol will release about 625g of C02 for every litre burnt, so assuming you burn 1.5 litres for your 50Km trip you'll generate about a 1Kg of C02 (Note: these calculations are based on figures for C02 in petrol from here)

so yep ... the petrol version generates less CO2 as well. It’s 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 an electric scooter equivalent to a 50cc scooter costs about $4250, while a 4 stroke *(more expensive, much cleaner burning less polluting than 2 stroke) Honda Scoopy will cost you about $2500

Yes, you did read that right, you'll pay nearly double for an equivalent electric scooter which will likely produce as much C02 (if that's of interest to you) and certainly more other significant toxic waste than will the choice of a clean 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 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. It’s worth noting that these are largely written by people who actually sell the electric alternative (but not the electricity).

It’s 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. 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)

So that's $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 during the day for charging ... sounds great to you too?

So in summary:

It seems like the following to me

· I will save a little per trip (about 80c for a 50Km trip vs $1.25)
· but I pay double to purchase ($4200 vs $2500)
· unknown depreciation losses (but it’s fair to say you can't lose more than $2500 on the petrol scooter)
· pay more for operational costs (the battery will die)
· 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 cannot 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 50cc to 110cc 4 stroke scooter stop driving your car and help save the world’s atmosphere and resources.


  1. Cameron

    not sure my comments about fishermen leaving stuff all over the beach is my most shining littery moment (attempt at mis-spelling pun) but to add to my final thoughts about electric scooters ... or even better yet ride a bicycle which you pedal!

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

    1. They don't. I will explain why he's plain wrong in a different comment.

  3. I actually thought the fisherman one was great - mostly because you highlight unintended consequences that are usually ignored.

  4. Good post and nice analysis. The figures for electric cars make them look even worse!

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

    Another point:
    The most efficient way of moving people around a city is human power - ie. a bicycle. An electric bicycle is technically a human-electric hybrid as the point is to not ride it like a scooter. It just gives some assistance (usually for hills or heavy loads). The rider does most of the work.

    Also, if you are going to electrify any form of personal transport (small scale) then the bicycle is the most sensible as it is already the most efficient means of transport. An electric car is really shifting a tonne of car...

    For mass transit, electric rail is the way to go...

  5. Great article
    Exactly what I wanted to find out

  6. You have explained nicely both petrol and electric scooter. If you have short daily commute and you don't wanna much faster then electric scooter is best otherwise petrol.

  7. I bought an amazing electric bike off them when it was on sale and they've been incredibly helpful getting to know it and use it. They are the good guys! electric bikes

  8. I know it's an old article and he's probably wiser by now, but his assessment that the electric scooter produces 3.6x as much CO2 is utter nonsense. Firstly he assumes an 100% coal-generated mix, which is a far cry from reality. Sure, maybe in SOME places the mix is rough, certain states or poorer countries, but last I checked coal is something in the range of 33%/mix in US and <20%/mix in Europe. Some countries/states, it's >= 90%! And don't forget, a) this power mix is becoming cleaner every year and b) nothing is to stop a home-owner from installing solar panels or a wind turbine.

    Secondly, his CO2 assessment makes the huge schoolboy error a lot of people make - he neglects to evaluate the entire process it takes to get petrol to your tank. Drilling, transporting, refining, transporting... these steps all release CO2 too!

    When you evaluate the ENTIRE well-to-wheels process of powering a combustion engine and compare it to a battery, it actually works out worse for the environment. And before you turn around and say "oh, but the batteries and motors are harmful!" STOP. It's entirely possible - just as Tesla are currently doing - to use motors and batteries that contain NO toxic materials and are almost fully recyclable.