Several weeks back, I posted about wanting to build an eBike. I started out by saying that the first part was to purchase a cheap used mountain bike locally, which I did. I've made various needed improvements (replaced the seat with one much more comfortable, replaced worn brake pads, etc), but it needs a few more minor tweaks.
In any case, from the advice I received on the previous thread, and from my own research, I think I've decided to go with the equipment from www.goldenmotor.com. The battery that they have is an SLA, but those are classically heavy, bulky, and from what I understand need to be charged immediately after use.
I'd like a battery that is as light and small as possible, and one that will accommodate my sporadic battery-charging habits. So I'm thinking of using NiMH batteries. The motor requires 36V. At 1.2V each, that's 30 D-sized batteries.
Here's what I'm wondering.. should I come as close to 36V as I can (by using 30 batteries), or should I try to go beyond 36V by one or two batteries to make sure that as the power is drained it remains at or above 36V for as long as possible? My understanding with NiMH (as opposed to alkalines) is that they will maintain their voltage all the way down to about 20% capacity. If that's the case, I would guess that using 30 batteries would be sufficient.
Or should I use something other than NiMH? One other advantage here is that they would be significantly lighter than SLA at the same capacity (right?), but they are also small and can be distributed on the bicyle (i.e. strapped to the frame) instead of a single SLA battery that would put a lot of weight and bulkiness on one portion of the bike.
What would be the best and fastest way to charge 30 of these batteries? I know I could break them down and use 8 4-battery chargers, but collectively these chargers would be expensive and also take a lot of space. Or can I break them into 10-battery segments and use a 12V charger that would be able to charge them quickly (1-2 hours)? Is there a specific 12V charger for NiMH?
