A 12 volt 7 amp lead battery is roughly, 3"x3.5"x6". That is really not very big. And, they can be bought for $17.00 to $25.00. A smart charger can be had for $10.00 and you can make or buy a voltage converter for around $15.00.
As for regulation. Depending on the current draw you could run a piece of equipment from 4-24 hours on one battery.
I run and Aerco MP2 mic pre-amp on a 12 volt 4 amp battery and it operates up to 20 hours or so. I can operate a Sony D10proII on a 12 volt 7 amp for 5 hours. If I worry about running out of juice I just bring 2.
Sure these buggers are heavy but at home they would just sit on your floor. As for corrosives, they are sealed and after using them in the field for over 10 years I have never had one leak.
They claim that they need to be recharged in a ventalated space, but that is not too big of a problem. You could use your basement or garage. I use my listening room. They do not let off an odor but apparently continuous, prolonged exposure could, (like 24/7/364) be harmful. Not, IMO, once every two weeks for 6 hours. Anyway, I do it overnight when I'm not in the room.
Sean, I agree with you regarding the manufacturer's battery supplies and it was my point exactly, "Their battery supplies seem to be way, way overpriced"
BTW, I run a portable CD player on a steped down 12 volt/1.7 amp, lead sealed battery for up to 12 hours of use. I charge it up, when needed and presto, for $5.00 I have let to buy batteries in the last 3 years. I plug that sucker into my Grado RA 1 and along with my RS 2 headphones I have a great portable system.
My next step will be to find a cheap/small D-A, which runs on DC and a portable CD with digital out for that last bit of rez.