Battery failing- help!

[Auldgit]

Hi, new member of forum, I have a problem with my daughter's electric bike. Bought three years ago on ebay, it has a 24v NiMh battery pack powering (I think) a 200W rear wheel motor. Goes well, used daily. We replaced the battery pack with a new one from the supplier after approx 12months, the new one has performed much better than the original, but is now giving notice. Contacted the supplier, sorry, can't do another one, factory closed etc etc.

I therefore need to get one made up, or as a last resort DIY, but there is no info whatsoever on the battery pack as to what capacity it is. It has 20 (presumably 1.2v) D size cells, but there is no indication on them as to what AH they are. Can anyone give me a clue as to what size of cells/pack I should be looking for??

And, any info on potential suppliers of cells/packs would be greatly appreciated. Not really my field this! More of a petrol head.........!

 

[flecc]

There are very few NiMh cellpacks or cells of good quality available now, due to lithium taking much of the market. However, I'd recommend a pack since that's the easiest to recell with and the best supplier of those is Batteryspace in the USA, despite the postage cost upping the price.

It's best to go for 10 Ah and you need a 20 cell pack, the cells D size. First determine the cell formation within your case, usually either rows of 7-6-7 to form a longish rectangle, or more rarely, 4 x 5 cells. Very rarely a battery will have the cells in vertical columns, and in that case there's no chance of getting a ready made pack.

Then have a look at the webpage below and choose the shape to suit, 7-6-7 or 4 x 5, but not either of the bottom two which use very large F cells:

Batteryspace

When fitting the pack, make sure you refit the battery's thermistor and it's connections exactly where they were before (the thermistor is a small bead like electronic part with two connecting wires, and it's in contact with a cell wall to measure the temperature and tell your charger when to switch off).
.

 

[Auldgit]

Thanks for that Flecc, my pack at the moment consists of four vertical columns with five cells in each column and wired in series, these fit into an alloy case which is attached behind the seat tube of the frame. As you say, not likely to find a direct replacement so will probably have to go for a custom job.

Thanks also for the link, v.useful.

One thing which puzzles me is the capacity of the made up pack, you recommend 10Ah, the pack offered by Batteryspace is listed as 10Ah, but it contains 20 cells each of 10000 mAh. As 1000milliamps = 1 amp, does not 10000mAh = 1Ah??, making the capacity of the pack 20x 1Ah =20AH??

 

[tillson]

Thanks for that Flecc, my pack at the moment consists of four vertical columns with five cells in each column and wired in series, these fit into an alloy case which is attached behind the seat tube of the frame. As you say, not likely to find a direct replacement so will probably have to go for a custom job.

Thanks also for the link, v.useful.

One thing which puzzles me is the capacity of the made up pack, you recommend 10Ah, the pack offered by Batteryspace is listed as 10Ah, but it contains 20 cells each of 10000 mAh. As 1000milliamps = 1 amp, does not 10000mAh = 1Ah??, making the capacity of the pack 20x 1Ah =20AH??

Each 1.2 volt cell has a capacity of 10 Ah. (10 000 mAh / 1000 = 10)

The cells will be wired in series (20 x 1.2 v= 24 v), and because they are in series, the total capacity of the pack will be the same as each individual cell. Therefore, you will end up with a 24volt 10 Ah battery pack.

 

[Auldgit]

Many thanks Tillson, too many noughts for me. I get easily confused these days.

auldgit

 

[dan]

Hi, new member of forum, I have a problem with my daughter's electric bike. Bought three years ago on ebay, it has a 24v NiMh battery pack powering (I think) a 200W rear wheel motor. Goes well, used daily. We replaced the battery pack with a new one from the supplier after approx 12months, the new one has performed much better than the original, but is now giving notice. Contacted the supplier, sorry, can't do another one, factory closed etc etc.

I therefore need to get one made up, or as a last resort DIY, but there is no info whatsoever on the battery pack as to what capacity it is. It has 20 (presumably 1.2v) D size cells, but there is no indication on them as to what AH they are. Can anyone give me a clue as to what size of cells/pack I should be looking for??

And, any info on potential suppliers of cells/packs would be greatly appreciated. Not really my field this! More of a petrol head.........!

try Bernie at Bikes and Batteries 01780 471010....I found him very helpfull with information about battery packs..

 

[Auldgit]

Thanks for that lead Dan, I'll certainly do that. Making SOME progress!

Cheers

AG