What size battery do I need??

[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.........!

 

[Psycosis]

I guess the only way would be to get more info about the type of kit. Even if the company has ceased trading i imagine there will be some info floating around.

It seems the NiMH batteries seem to generally come in at about 10amps, someone feel free to shoot me down at this general assumption.
I am basing this on what i have seen, and the fact its only a 200w motor, seems unlikely they would have sold something bigger.

How big is the battery physically?

You could alwasy try getting a LiFePo4 battery, most likely come in at a reasonable price e.g.
24V 10AH V2.5 LiFePO4 Battery Pack
$199 for a 10amp 24v battery and $60 for shipping to the Uk.
In pounds £159 plus any tax you get hit for.

 

[Auldgit]

Hi, can't find any info re bike, it is one of the many cheapo Chinese imports. No manual of course......you get what you pay for. Lightning is the name on the frame. I'd prefer to stick with the Ni Mh if at all poss as I have a charger etc for that type, the size isn't critical as I doubt if i'll get anything to fit into the existing battery case, unless I DIY, so I'll be looking to mount on the rack or in the panniers. It's just a question of sizing the thing really, there seems to be a wide range of cells available from 2000mh up to 10000mh in D size, and I don't know what to aim for.

 

[Memran]

I'm confused about your reasoning here.

As long as the physical size ("D") and the number of cells is maintained, the capacity of the cells should be simply "as big as possible". You just need to balance maximum capacity against cost.

 

[flecc]

The NiMh D cells for e-bikes are typically 8 to 10 Ah size, but they do need to be high discharge types. The problem is that the adoption of lithium batteries has meant production of this type of cell has all but stopped and the very few still available are expensive, often £10 to £11 per cell for tagged types.

You may find a pre-formed pack will fit your casing, and the best supplier for those is Batteryspace in the USA. Here's the webpage you need, and from that select the pack formation that fits your bike, making sure the capacity is sufficient:

Batteryspace 24 volt packs

Your formation is probably the 3R767, three rows of cells, 7 cells, then 6 in the middle and 7 the other side, but there other less common shapes and formations there.

Bear in mind that one sometimes gets caught by customs for VAT and import duty on top, something which is a matter of luck.
.

 

[Sevenhills]

Hi

I havnt looked at what I need yet, but I have my doubts about the battery on my izip. If I bought a new battery, do they do kits to fit into my on ixips battery case that fits on the rear rack?
Or is it just a matter of DIY?

NiMH Battery & Charger Combo: 24V 4500 mAh (20xSc) NiMH Battery + Smart Charger (1.5A)

S

 

[flecc]

Is your Izip currently using lead acid (SLA) batteries Sevenhills? If so, to change to NiMh you'd need to measure your case interior dimensions and ensure the pack you choose would fit in, using the sizes quoted on the Batteryspace/Powerizer websites.

If none of the listed packs fit, it would have to be a DIY pack build, using loose cells and an appropriate thermistor.
.