I'm sorta surprised no one else has recommended to be real careful with 192VDC.
In my paranoia, I'd put a fuse every couple of batteries or so, just in case I cause something to arc. A 120VAC arc is not so bad, since it crosses zero potential 100 or 120 times per second or so, but a 192VDC arc would be very hot, and possibly tricky to extinguish while you're panicking your arse off. (At least that's what I'd be doing.)
However, it does bring to mind a question I have had in the back of my mind for a while. If you put 10 12V batts in series, you'd have 120VDC. For 10-20 bucks worth of parts (timer, some power transistors) you could make a cheapie squarewave inverter and power certain items. I'm thinking CFL's and stuff with transformers like computers and stuff. (The transformers themselves would probably smooth out your wave enough to work properly.) Actually, if it's a squarewave you'd probably have to diddle with the duty cycle and/or input voltage to get the correct RMS, but you probably get the idea.
Or if you have a fast circuit, you may even be able to use some PWM to simulate a MSW. (Yeah, I just used those two TLA's together!) Say, if you could switch on/off with accuracy down to 1ms or so, then you could use a 1ms on, 9ms off duty cycle when the wave is supposed to be at 12V, 1:2ms cycle at 40V, 1:1ms at 60V, 2:1ms at 80V and so on. You could get pretty close to a sine wave that way, and it would be quite efficient.
Hmm... have I gone nuts? Or is that how MSW inverters work, basically? But my point is, it could be way more efficient with 120VDC coming in instead of 12V or 48V, right? Or does it even matter?
If it's less electronics, and less current to use 120VDC instead of 48VDC, it's quite tempting.