Hi Glowboy, thanks for the excellent question.
I am still running the same 35W SoLux (4100k color) with the batteryspace 14.4V nimh. It's only 5AH, but this gives me over one hour of run time, which is perfect for my commute. It's extremely bright. Also, I would highly recommend overvolting with halogens, the only supposed reason not to is decreased bulb life - but let me tell you I've been running the same bulb at least 5 days a week for 6 months+ with no signs of slowing. As far as your battery choice is concerned, it's up to you but my recommendation would be to stick with nimh because it's cheaper and the slight weight difference doesn't matter much if any to a commuter.
Originally Posted by GlowBoy
Paging NeezyDeezy (and others) ... halogen overvolt question:
ND, looking through this thread I just noticed you're running MR16 halogens (SoLux) directly off a 14.4V NiMH battery.
Any problems doing this? While I'm asking, anyone else driven halogens directly off a 14.4V (or, for that matter, 14.8V Lithium) battery, successfully or unsuccessfully?
Sadly, my original 12V battery is starting to give up the ghost, so it's time for a new one. But turning lemons into lemonade, buying a new battery does give me an opportunity to step up and take advantage of overvolting. I don't see why not to go all the way to 14.4 as NeezyDeezy did. And since I'll need a new charger anyway (my current one is 12V max), nothing is off the table -- including 14.8V Lithium. I need to think about this over the weekend, but the options I'm considering (from batteryspace) are:
- 14.4V x 5Ah, $75 including charger. Would require me to stick to 20W bulbs, but a 20W Philips bulb driven at this voltage will put out the same amount of light as my current 35W SoLux driven at 12V.
- Lithium 14.8V x 4.8Ah, $100 including charger. Same bulb situation as above, but only $25 extra and the battery weighs 1/3 of what the NiMH does. That's about 3 cents per gram saved! I'd be very hesitant working with bare Li cells, but the product I'm looking at minimizes the safety issues because it comes prepackaged in a water bottle with protection circuitry built in, literally plug and play. Very tempting.
- Lithium 14.8V x 7.2Ah, $160 including charger. Big enough to comfortably run a 35W SoLux, which I do prefer because of the bulb color and the 17* beam pattern (Philips bulbs are either a bit too narrow or a bit too wide for my taste). And at 14+ volts it will be about double my current brightness, true car headlight territory. Could be overkill, but there have been some dark rainy nights where I wouldn't have minded even more light than I have now. How important is that to me? I guess that's the $160 question I need to ask myself.
I'm not sure which option to go with, partly because I'm trying to decide how much light I want, how important it is to me that I can run SoLux bulbs, and how much I'm willing to spend (after the initial shock that I have to spend any money at all). I need to answer those questions for myself before I can make this decision, but I'm still interested in anyone else's input on driving 12V halogens off 14.4-14.8V batteries in general, and on the options I'm considering specifically.