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.