Electric Bikes - making battery pack

been looking at the F size 12 ah nimh battery range,specs say standard operating 12 amps,max continuos running 40 amps would these batteries make a pretty good home made pack?i see 22 of these can make a 26 volt 12 ah hours pack for around $300 australian.they seem like a good compromise between the heavy lead acid pack and the expensive lithium packs.

I have 1300Ah NiMh F cells and from my experience they lose a lot of charge in just a day or two. And if they don't see regular service they become even more sluggish about holding charge until a few cycles. Also, 40A drain is the BEST you can expect. It seems my F cell packs are happiest around 20A max.

They also exhibit cell imbalance issues in long series strings which require almost as much charge monitoring/conditioning as Lithium. But, they seem to have a good, long shelf life if kept in balance and not abused by high/long cycles.

Seriously, lithium chemistry is the stuff that will make a weight difference. NiMh barely any at all and by the time I factor a reliable range margin for my non-daily use with these NiMh cells, I'm usually carrying more AH capacity than SLA on the same bike. I see little to no weight savings with NiMh in my situation. Lithium on the other hand, is an easy 1/4-1/3 weight savings for comparable AH/WH range capacity of SLA.

That's my experience - your mileage may vary. Good luck!

Well, I don't know personally. Is that cost *including* your charger, packaging/wiring and connectors or not? You can buy a complete lithium system starting at around $430, ebikes.ca off the top of my head, has NiMH packs that are probably about the same price as that pack. Remember that you'll probably only need 8ah of lithium to equal 12ah of SLA, and its probably pretty close to 12ah of NiMH.

the cheapest i could find a lithium pack here in sydney was a 36 volt 10 ah was around $750 australian with charger,mmm i guess it is beeter to spend the extra and go lithium then,the nimh price was just the batteries alone.

Is the DeWalt 36 volt battery an option?

well i got my set of TWO 36v 12ah LiFEPO4 packs including charger and shipping to my door for $1100ish

after experiencing the light weight and crazy power delivery of lithium, i will NEVER go back to lead - EVER.

I used to have 4 17ah 12v jump start batteries. 2 of these were duct taped together and wired in series - 2 in each panny bag (2x 2 = 4) for 48v.

the 72v dual-pack (yes its 12ah - but i'd say its equivalent to the 17ah SLAs) fit in ONE panny bag and weighted 1.5kg more than 24v 17ah of lead.... so a little over half the weight/size for a little under twice the power.

for ~$550 a battery & charger i would never hesitate to buy LiFEPO4 over EVERY other chemistry (with the exception of maybe LiMn - found in makita and millwakee powertools).

I got my batteries from yesa (missbattery on ebay - search for lifepo4) tell Sam Haydon sent you.

after experiencing the light weight and crazy power delivery of lithium, i will NEVER go back to lead - EVER.

Ditto - well, do as I say not as I do! I have all 3 chemistry's and still use them all - SLA, NiMh F cells & A123 Systems developer kits. But, I'm only using the SLA & NiMh because they still work and I gotta chunk of money into the NiMh but once they're done - I won't bother with that chemistry ever again for eBike/eScooter applications. Lithium only for me too!

Good to hear about your recent deal BiGH - will tell 'em you sent me if/when I need some more. A123 Systems developer kits have been great but I had to build/modify my own charger and it's still fairly manual monitoring/balancing, etc. Expensive too and much trouble for my limited time to build - turn key solution is probably best.

Is the DeWalt 36 volt battery an option?

It can be and has for some folks - trouble is only 2.3AH per pack. You can parallel wire packs to increase capacity but it get's weird about charging more than one pack at a time with the stock charger and then their BMS circuit also controls output so that's another problem to rework, etc.

Milwaukee 28V actually have a simpler BMS for our applications and you can buy the bayonette mounts as part for a quick change arrangement on your rig. But, they're different cells and I have no 1st hand experience with those cells like I do with the A123 (Dewalt).

mmm i will pass on that chinese offer from missbattery dont know anything about that company and no one else seems to know either,might still do a nimh pack until lithiums come down in price abit.