Is this worth buying?

[Bigbee]

Ive just been to try a second hand electric mountain bike advertised in my local rag.It looks a bit like a Wisper,but the bike had no name on it .The bloke said it had a 200w motor and a 36V 8 ah battery.He said he was selling at £150 as his job had changed and he didnt have time to cycle any more.It was in pretty good nick.It had a switch for PAS only or PAS/throttle.I took it up the road which had a little incline.At first it was brilliant and I was going to rush back and thrust the money at him,then it seemed like it was cutting out.I turned it off and on again and it was alright for a while then it went again.I switched to throttle and that got me back to him fine.I told him I needed to think about it.Is this a common problem and can it be fixed easily if say the PAS sensor has gone?If I can get it sorted cheaply it'll still be a bargain and I might be able to get some off the price.

 

[flecc]

It sounds like it's a Li-ion battery (lithium) and at the end of it's life, hence the cutting out. If lithium and even if you could get a replacement battery, it could cost you anything from £200 to £400, depending on it's voltage.

Not worth buying until you establish the battery type, whether replacements are available and how much.

With this battery type and with power applied, the cells drop below cutout voltage when they are worn out.
.

 

[Bigbee]

Thanks flecc,but why would it work ok on the trottle?

 

[flecc]

Thanks flecc,but why would it work ok on the trottle?

You may have been using part throttle rather than full, in which case it could have stayed within it's capabilities, where the pedelec power was probably at full.

However, if you were using full throttle, it could be something else. Bear in mind though that lithium batteries only last about two years at most, and the cheaper ones have been failing well short of that, so that could still have very little life left. Therefore the availability and price is still very important.
.

 

[Bigbee]

I was on full throttle and pedalling too.I might see if I can scout about for a 36V battery cheap some where,it was 36v,does it have to be 8ah or can I use any ah?

 

[flecc]

If using full throttle, it does sound like the PAS sensor or connections, so you could just use it on throttle only.

Any Ah will do, and it doesn't have to be a lithium battery. Of course if you aren't using the correct battery you'll have to stick it on the rack or somewhere else.

Lithium batteries are all pricey and NiMh are hardly available any more and almost as dear. The cheap option is lead acid, 3 x 12 volt SLA batteries in series at about £100 or thereabouts, but they are very heavy and have less range for their Ah capacity. You'd also need a new charger for it.
.

 

[Bigbee]

Thanks for your advice,I'll sleep on this.I may give him a call to tell him what really happened when I tried the bike and see what he says.

 

[eddieo]

is there not a company who rebuilds battery's?

or use a different one.......

 

[flecc]

is there not a company who rebuilds battery's?

None for lithium since each make has a different BMS and there's no standardisation of cells or BMS.

There used to be some recelling services for NiMh, but lack of good high discharge cell availability and their high prices has killed that too.

Now it's just DIY with SLA, NiMh cells of unknown quality, or importing LiFePO4 from Li Ping in China.
.