Kit specifies minimum AH for battery..

[AliBaliBee73]

Hi there - going to buy a Voilamart front wheel 500w kit to dip my toes into the world of Ebikes. Was going to use that with a Stihl 36v 5ah battery I have from my gardening job - job done I thought but it specifies that the wheel motor needs a minimum of 10ah. After googling I still can't work out why, except maybe the battery will be working too hard? The cells in the Still battery will be of a high quality as their driving chainsaws etc. My commute is only 2 miles, I'm probably going to try it out anyway and see if it's ok , but does anyone know why this isn't a great idea? Is it possible to damage the motor or just the battery - or both?

Thanks!!

 

[sjpt]

I think the Voilamart 500w kit is a direct drive motor. As well as being illegal (*) in most situations it is very inefficient; heavy on battery with poor hill climbing capability. It's only good points are that it is cheap and can go (illegally) fast on the level. Most 250w geared motors are much more efficient and can generate much more useful power without needing a big battery.

What is important for a motor is the battery amps (how much can the battery deliver at any time), not the amp hours (how much total energy it can hold). If you are using 10 amps at 36v then the power consumed is only 360 watts, the power generated by an efficient motor maybe 280w at best, and by an inefficient motor a lot less than that.

The amp hours will dictate range, with that sort of motor you will probably only get 1/2 hour from a 5ah battery; still enough for a 2 mile commute each way.

For a 2 mile commute you are probably best off on a regular bike unless there are special reasons (eg steep hills, health)

(*) but low risk of being caught

 

[Benjahmin]

These motors are direct drive, they are power hungry and inefficient. The spec doesn't say the current rating of the controller but, because of said inefficiency, continuous current draw will be high. Therefore the battery needs to be not only large capacity but capable of delivering a high continuous current without cells overheating.
We see a lot of people here with these kits, my advice would be not to buy it. The kit may be cheap but the battery needs to be top class to run it. Also, being gearless, they only come into their own on the flat at high speeds, gutless for hill climbing.
Get a decent 250w geared kit with decent current control and you'll be able to use the battery you've got.


p.s. crossed with sjpt's post.

 

[AliBaliBee73]

Thanks for that excellent reply!

To clarify , my reason for ebike is so I can come home for lunch (which I’ve been doing by car.) but would like to put less strain on the car and use less fuel. I can get to work on farm tracks (I’m very remote) - but I’d like to do it as fast as possible so I have as much time at home as I can. Not silly fast but 20mph. It’s fairly hilly in places so maybe the geared is better but not sure where to look for such a good price (c£150).
I’ll look into the differences more - I had just blindly assumed direct drive would be better.

thanks again!!

alastair

 

[AliBaliBee73]

Ps I cycled it on a regular bike and it took me 22mins for the 2 miles - too slow!!

 

[Nealh]

D/D makes sense if you have a flat fairly interrupted route, then at fast speed they excel and are in the efficient zone. Other wise for hilly commutes one needs to throw serious current through them which means about 35/40a and a battery to deliver, with a spec rating much higher then 40a.

One first needs to know the cell type and amp rating in the Stihl battery, the cells will be 2.5ah each but we don't know which type of cell. likely they may be a high drain Sony. The Voilamart will likely use a 20/25a controller (with no link to product a guess) but the issue is poor performance at 36v for a hilly climb.

An ebike will likely knock about 5 or 6 mins off the journey time each way, so don't expect it to be a 10min job.

 

[vfr400]

Voilamart kit is 22 amps. The battery will,be limited on how many amps it can supply by its BMS. It'll most likely trip at that current. The 5Ah is at 0.2C. At your current of 4.5C, you'd get about 3.5Ah out of it. If it works at all, thats 3.5/22 x 60 = 9.5 minutes use. Trust me, you won't want to pedal that bike with the kit fitted and no power.

 

[AliBaliBee73]

Thanks for all the replies. Seems a 250w geared is the way to go, but then maybe I'm dreaming to think I could do the journey in 8 mins ( average 18mph, 2.4 mile journey ). I guess it's a trade off between faster straights or faster hills, aside from battery issues... Seems the Stihl might work for a similarly priced geared motor better. Your advice has been great thanks.

 

[vfr400]

The cheapest kits work, but or not very-user-friendly. I'd advise you to pay a bit more and get a geared hub-motor kit (normally rear) that has an LCD and 5 levels of assist. The most desirable ones have the KT controller and LCD3. If they mention LCD3, then it's probably a KT controller.

When you have such a kit installed with a decent battery, you'll find that you'll start using your bike for other journeys than commuting, and maybe just go out to ride for fun and fresh air.

 

[AliBaliBee73]

That’s probably really good advice but my cheapskate self says I could get a samebike 500W entire bike for not much more money so I can’t see the point in self build unless it’s cheaper than an entire new ebike even though it’s probably a better experience. I’d love to have the best but this one is definitely on a budget!

 

[vfr400]

That’s probably really good advice but my cheapskate self says I could get a samebike 500W entire bike for not much more money so I can’t see the point in self build unless it’s cheaper than an entire new ebike even though it’s probably a better experience. I’d love to have the best but this one is definitely on a budget!

The reasons for conversion are:

• You have a bike that has characteristics that you want or need that you can't get on a ready-made one.
• You like doing projects and you like to learn how things work.
• You want special characteristics from the electrical system that you can't get on an OEM bike.

Cost is rarely a justified reason to convert. Cheap kits rarely give a satisfactory result, though you can get some quite nice kits cheaply from Xiongda and MXUS if you buy direct.

 

[AliBaliBee73]

Thanks for the advice - and because of the advice I think I'm settled on getting a Yose Power 250w front geared hub kit at just under £200. Hope that's a better choice than the bulky 500w voilamart DD motor.

 

[sjpt]

Good luck with it. I'm sure you won't regret it.

 

[AliBaliBee73]

Just an update.

I got the Yose Power 350w rear hub and a 36v 12ah battery. Fitted over a few evenings to a crap old Apollo mountain bike.

Did my commute in 9 minutes so way better than 22, overall very happy with the kit. Bit worried about the waterproofing of the controller that's built in to the battery install as it gets all the crap thrown at it in the position it's in on the down tube. Seems to max out at 20mph even though in settings I have it at 25. Thats ok though on this old bone shaker, I'll probably invest in a lighter and more modern donor bike in the future (with better brakes...)



Thanks for all the help!