DIY electric Brompton: Reviewed after a couple of months in service.

[Drago]

Probably no more or less than about 75% of the battery vendors out there. It'll be treated with the same levels of suspicion as all the Li-Ion batteries I own.

You'll need a bit more than suspicion to help you if it goes all willie-pete on yo' ass.

Unless you're charging it outdoors, 10 or more metres from the house, you'll need more than suspicion to protect you, like a 3" thick cast iron box with asbestos lining.

I've heard of folk putting them in biscuit tins and the like thinking that'll protect them if it goes off. It won't.

As for the rest of it, great project.

 

[albion]

That seems cheap... does it include a battery?

EDIT: even if it does, apparently their standard battery is only good for 9 miles...

Tiny battery. Good enough for short commutes.
A fit for the typical Brompton user.

 

[templehead]

You'll need a bit more than suspicion to help you if it goes all willie-pete on yo' ass.

Unless you're charging it outdoors, 10 or more metres from the house, you'll need more than suspicion to protect you, like a 3" thick cast iron box with asbestos lining.

I've heard of folk putting them in biscuit tins and the like thinking that'll protect them if it goes off. It won't.

As for the rest of it, great project.

It won't be in a biscuit tin. It'll be charged in a metal shed far enough from the house not to matter if it goes up, along with the battery from the Dawes and the two 72V packs from my Bumblebee Classic.

 

[templehead]

Now the hysteria about the battery is out of the way, let's see about that refund:

Result! Definitely worth the five minutes it took to complain. More when the front tyre, tube and throttle turn up...

 

[templehead]

Bit of progress... front wheel is on, and I've made up the bracket that will carry the battery... main job was extending the shelf upwards with a piece of 2mm chequer plate:

The battery slides on downwards and can be locked in place with the supplied key. The handlebars can still fold down so we're all good on that front.

Next job is to find a suitable place to site the controller box.

 

[templehead]

The box I bought for the controller was a seat post one, therefore the brackets won't go round the Brompton's fat crossbar, so I cable tied it on for the purposes of running the wiring. I'll find a better way of achieving the same thing when I have a bit more time, possibly a couple of U-bolts?

The main loom with connectors for throttle, brake levers and instruments is all plugged in and tidied up, next job is to join up the battery leads and find a bit of flexible conduit to keep them safe. I also need to order a motor extension cable, as the one in the kit is about a metre long and I only need about 200mm.

Then I've got the problem of the motion sensor to deal with... the disc with the magnets is fitted OK but the kit comes with a sensor on a spring and a couple of bits of double sided tape... bodging this isn't an option (I'd rather not anyway!) so I'll have to have a root around and see if I can find something appropriate in the garage. Hopefully not long now until it's on the road, more soon...

 

[templehead]

Pretty much done now, there were two major snags - one was that it was the fastest reversing Brompton ever until I put the front wheel in the right way round (there are no markings to indicate which way the motor runs!). Second is that the pedal assist sensor is a dud. Fitting it was a bit fiddly as it was a generic thing not in any way designed for a Brompton, so I ordered a bag of cheap handlebar clamps etc. from Aliexpress (£10 posted) and improvised:

A replacement has been ordered (£3). The test ride was completed by using the throttle, and I'm pleased to say it goes very well even if the bike itself handles like a five bar gate. Seriously, the cheapo Btwin folder I used on holiday last year was better. Anyway, the main thing is that it goes and it still folds up without kinking any mission-critical wires.

It still needs some fettling, e.g. some flexible conduit for the battery wires and a better method of fixing the controller in place, but once the new sensor comes it'll be ready for service.

In conclusion, then, I'd say that this 'Brompton kit' was anything but; it's a 16" wheel and a load of generic e-bike parts, so if you choose to go down the DIY road be prepared for the sort of alterations that I've had to make. All in I have spent just shy of £400 on the conversion, which I'm happy with.

FIN

 

[templehead]

A small update, for anyone interested, now that this device has been in use for a couple of months... the battery has a range of around 20 miles, which is pretty crap for such a massive device, but entirely expected based on cost and fine for the intended purpose. I've been charging it at 15 miles so as not to be running it too low.

The motor has had the added bonus of making the left-hand gearshift redundant, the three ratios I can get using just the R/H lever are plenty now. The crank sensor only kicks the motor into life after about 3/4 of a turn, so the throttle is handy for getting it moving on the many hill starts it and I have to do.

When folded, the weight of the aforementioned battery is all on one side so it had a tendency to fall over rather than roll. A set of big castors with an extending axle from Aliexpress (about £14) fixed that.

Overall, I'm pleased enough with the end result. I think the terrible clown-bike handling would get to me if I had to ride it any great distance (some people tour on these things?!) but for the job in hand, based on what it has cost me it's just fine.