Electric Bikes - Lithium batteries in series?

Hi all,

I'm currently riding a Crystalyte 350 watt 408-4011 motor with two 24V NIMH packs set up in series for 48V total.

I'm thinking of getting two 24V LiFePO4 15AH packs and setting them up the same way, in series for 48V output. Is this doable or are there other considerations that come into play?

Thanks in advance for any tips on this.

Here's the seller on ebay:
http://cgi.ebay.ca/ws/eBayISAPI.dll?ViewItem&item=220212536394&ih=012&category=11332&ssPageName=STORE:PROMOBOX:NEWLIST#LIST

If one of the packs has a different discharge curve/behavior then the other the first one to discharge could be damaged by the second upon deep discharge. The seller lists 48 volt packs. I rather go that way if I needed 48 volts.

If you buy two packs from the same maker, same amphour and voltage rating, and put them in series, it should work fine. You probably don't have to worry about one pack causing the other to over-discharge, because the low voltage cutoff circuits will prevent that from happening whether or not the pack is used in series.

Like ken said though, you're better off using a 48V pack if you can, just in case the battery management electronics get damaged by being used in a series configuration or something else odd happens.

Okay, there are some caveats but it seems doable. I've got a message in to the seller to see what they think.

It seems to me that two 24V 15AH batteries are a better deal than one 48V 20AH battery.

I can get the two 24V batteries for around $400, which would give me 30AH total.

The 48V battery is 20AH at $423.

Also, I use an underseat pannier rack on my EZ-1 to carry the batteries, so having one on each side is optimal in terms of weight distribution as well.

Actually, you'll end up with 48v/15ah, not 30ah.

You would need to run 4 of those batteries in a combination of parallel and serial together in order to reach 48/30.

Okay, I get it, sort of. I guess if the two were in parallel at 24V, that would be 30AH.

The ebay seller says putting them in parallel or series will damage the BMS, so it looks like 48V/20AH is the only way for me to go.

Its the safest, most convenient way to go. 48/20 for $423 is an incredible deal too, IMO, and thats 960 watt-hours, which is a very formidable amount of range.