Light is a VistaLite VL-420 (two of 'em, actually); it uses a 6V, 2.5AH Sealed Lead battery. It's made from three 2V, 2.5AH D-cell format cells, with soldered leads, wired together in series, with a coax plug that goes into the light. The charger is just a wall-wart that plugs right into the battery wire.
The batteries will no longer take a charge. Between the two battery packs, there aren't three cells that each charge to a full 2V, so I can't frankenstein one good pack out of the two. I'm considering alternatives to simply buying new SLA batteries (or buying the single cells and rebuilding them), in part because I'd rather buy something more environmentally cool than batteries full of lead.
Here are the choices I'm considering:
- Get or make a battery holder, and buy four (or five, if they're 1.2V) NiMH AA batteries in the 2.0-4.0 AH range. Wire the battery holder to a coax plug to plug into the light. Charge the batteries in my existing AA NiMH charger.
- Buy four or five NiMH batteries, with tabbed contacts, in any format that will fit, in the 2.0-4.0 AH range. Build a battery pack with the coax plug. Charge it using the wall-wart charger that came with the light.
- Status quo. Break down and buy (or build) a SLB pack, and charge it with the wall-wart.
- For option 1, I've found a really good deal on 2.0AH AA's. But since the original battery was rated 2.5AH, what will be the implications? AFAIK, it will simply mean the life per charge will be about 20% less, right? At 6V, it'll be just as bright, right? One advantage of this option, too, is that the batteries will be interchangeable with my digital camera, my existing Planet Bike headlights, my police scanner, etc.
- For option 2, Will the wall-wart charger properly charge the NiMH batteries? Does anybody know about the charging characteristics of NiMH batteries, compared to SLB's? I don't think the wall-wart has any faincy 'lectronics in it to detect the charge level of the battery it's charging (or am I wrong?).
- Generally, does physical size matter? (Of the battery!) I mean, if I put together five 1.2V, 4AH AA cells in series, I'll have a 6V 4AH battery pack, with the same per-charge life of any 6V 4AH battery, right? And generally, do I multiply charge (AH) if I connect in parallel? I was thinking of putting 10 2AH AA's together, that is, a series-pack of five, in parallel with another series-pack of five. Does that sound right? Or should I make five little packs, each consisting of two in parallel, and string them together in series with each other?
Any other ideas?