It looks like most of the Crystalyte Kits come with SLA batteries. Are there any companies that allow battery substitutions on their kits so you can upgrade to NiMH batteries and pay the difference?

Most kit suppliers I've spoken to about this say they don't mind subtracting the cost of SLA's from the kit. But, will they have alternatives - that's the other part of your question? NiMh isn't that much weight saving over SLA and if you don't ride/cycle daily, it will not deliver full range when you need it. The other downside to NiMh/NiCd is finding packs with high power output capability. Most eBikes will be okay but high power motor users will quickly run into limitations above 30-40 amps.

IMO - the best alternative to SLA at this time is high power lithium. If you can't find/afford something decent in that chemistry, stick with plain, cheap SLA until you do. Last I heard nickel prices were pushing NiMh/NiCd prices higher too.

BroadwayJoe, thanks for the reply. I can afford lithium ion and lithium ion polymer, but I am confused and not sure how safe and dependable they are. What's your take on their safety and reliability?

Just don't mess with cobalt as I understand things. I use A123 Systems developer kits, modify my own chargers and monitor cell balance every once in a while. I've abused 'em pretty hard and nothing has ever gotten out-of-hand in about 100 cycles.

Since they're used in Dewalt power tools, I would assume there's not too much danger. But, you gotta be careful with LVC (low voltage cutoff) - lithium dies quick! Nothing like SLA in that regard. That's why for some of my eBike folly I've learned to use multiple packs so that when one dies, switch over to a fresh one.

They need a little understanding and a lot of monitoring is the only downside I've experienced in over a year of use.

I bike 48 kms a day with my motor assist hub. Even the high amp hour SLA wouldn't cut it and you can't fully discharge lead acid that often before it becomes landfill bait.

I bought a NiCad 36V knowing that they LOVE to be fully discharged and have a greater charging cycling capacity. They also weigh about 1/3 less. That was almost 9 months ago and I'm still going strong without any noticable loss of power. The only downside I can see is that they heat up when discharging quickly, so you need to make sure there is a summer and a winter pack holder.

Also rumour has it that they need the occassional full discharge or you might not get the number of re-charge cycles you are expecting.