Introduction
Back in 2011, I was in the market for a new motorbike. At the time, I had a 25 mile commute (50 miles in total). As it happened a local motorbike dealer was trying to introduce a low power Chinese electric scooter into the UK. Although, i still wanted a ‘fun’ bike, getting a scooter for commuting made sense for me, especially an electric one. The scooter in question was called an E-Motive E3. It had a 4Kw motor and approximately 4KWH (20 40AH Lithium batteries) of storage, with a top speed of about 40Mph. On paper the range was about 40 miles but this was back in the day when mileage claims were a bit ridiculous. I only needed it to get a distance of 25 miles (I knew I could charge in work), so I took a gamble and bought one as it was only £2000 new. The best part about this was that it only cost 1p a mile to run. So, my commuting cost suddenly dropped to £2.50 a week. There was no tax cost and insurance was practically free. It seemed ideal.
Strangely in all the time I owned the scooter, I never took any complete pictures of it, so here is the best I have:
Real-world Range
I was a little nervous during the first run to work. Of course now I know this is called range anxiety. However, the batteries were new and it was summer, so the bike made it with no problems. I charged at work (it only took 3 to 4 hours) and rode it back. I began to believe that maybe the claims of 40 miles range were true. One day, I did a local test run and it was flat at about 32 miles and that wasn’t at full throttle. My estimate was that at full throttle it would probably do 28 miles. That was EV lesson number 1 – there is a big difference between claimed range and real world range.
Winter arrived and the bike now had a few miles on it. Then it started to get a bit more touch and go as to whether I would make it. Eventually, I started to ‘just about’ make it, depending on temperature. There were a few times where I had to push the bike the last few hundred yards. I had fitted heated hand grips but I had calculated how much energy they used and it wasn’t that much. That was EV lesson number 2 – temperature can drastically affect range.
To be fair though, I was pretty much full throttle for the 40 minute commute to work and found if I took it easier I could get more range. I also found that if I ended up behind a lorry and it was sticking to the speed limit (so I could keep up with it) a lot less energy was used. EV lesson number 3 – how you ride it makes a big difference in terms of speed and wind resistance.
I lived with this situation for the first year and when summer came round again, it was no longer a problem. However, I knew I would have to do something before Winter, especially as the batteries would be another year older by then.
I read up about the types of Lithium batteries and did a lot of research. I worked out that I could by 50% bigger LiFePo4 batteries for a reasonable price (£1500) from eBay. I was kind of hooked on the cheap commuting and this point so I was prepared to pay for it as I was intending to keep the scooter for as long as possible. So, for the second time I took a gamble and bought them. I knew they were physically bigger than the cells that were in the bike, so I had no idea how I was going to fit them, but I like a challenge. The cells were Winston LiFePo4 60AH.
I did some test charges on the battery to make sure that the bike charger would cope with them, there wasn’t a problem. Although I could have switched the charging current and voltage if it was necessary.
The way the bike is set up is that all the cells are in series and there is no cell balancing going on as it is a pretty low cost scooter! So before putting all the cells in, I at least wanted to make sure they were balanced by doing it manually.
Fitting the Batteries
Then came the difficult part. I completely stripped the bike so that I could see how to arrange the 20 cells.
Then it just became an exercise of measuring and test arrangements to see what the possibilities were. At more than one point, I thought it was not going to be possible.
However, after various paper exercises and wiring arrangement tests, I found a layout that I thought would fit without modifying the frame. A little bit of welding and painting later and I ended up with this:
In order to clear the frame, there had to be a narrowing of the box in the middle which resulted in an interesting arrangement of batteries!
Another problem I had with the new batteries was these terminal covers:
As the new batteries were bigger, the terminal spacing was greater. The new batteries were supplied with copper strips for joining together but not with covers. Covers for the terminals are quite important when you are dealing with lithium batteries. They can easily weld metal together.
So, a quick bit of design in openSCAD and some 3D printing.
After test fitting the batteries in the scooter without connecting all of the batteries up yet, they looked like this:
Battery management
I knew that I may want to put in some form of individual cell management at some point in the future. So, I wanted to put in a connection to each battery before reassembling the scooter. To keep these connections safe, I decided to fuse each wire. So, I bought 20 mini blade fuse holders and 3D printed fuse holders and some fuse cable identifiers.
I managed to find a space near the back of the bike frame that had space for a set of ten fuses on each side of the bike (after designing a mount for them). I would get back to wiring them in some time in the future.
Range Extended
I increased the tension in the rear spring to compensate a little for the extra weight of the bigger batteries. Because I had spread the batteries over the length of the scooter, the handling actually improved – it became even more nimble. The ABS brakes didn’t have a problem coping with the extra weight. The controller also worked fine.
After doing a test ride, the range really did increase by about 50%. So from a maximum of 28 miles in the summer, it increased to about 40 (finally!). Even in the Winter, the range was still around 34 miles. Another good feature was that because the batteries were no longer going completely flat during a commute, they would be under much less stress.
I continued to ride the bike for years with these batteries in it. However, I did perform some other modifications which I describe in part 2!
