On Saturday 02 July 2011 18:21:27 Jason Pyeron wrote: > > > > But surely computers actually use DC, so couldn't my > > > > torch-battery > > > > device just supply the PC components directly? > > > > > > A PC uses several *different* DC voltages: +12, +5, +3.3, > > > and several > > > others and they need to be *precise*. Some of these are > > > not an exact > > > multiples of the standard 1.5V Carbon-Zinc cells typicaly used in > > > torch batteries. > > > > I wonder, how is this issue solved in laptops? They use only > > one DC battery, typically with a single voltage output, AFAIK. > > (sorry ctrl-enter sends...) > > Laptops, google mother boards, etc have power supply circuits on board. > Remember that a switching powersupply taking AC still has dc to dc > converters in it after the conditioning stage. So couldn't the OP then plug a battery "in between" (I'm talking in principle here, not realistically) --- after the AC-to-DC stage but before the "conditioning" stage? If a laptop can have several *different* and *precise* voltages from a single DC battery, why the desktop cannot? I am not saying that it would be easy or cheap, just that the above "different voltages" argument seems false from my POV. If a laptop can be battery- powered, so can a desktop (given that you have all the hardware to implement it). You don't need to tweak the motherboard, just the PSU. It's routinely done in laptops, so it doesn't seem to be rocket-science or something too expensive. I wonder why aren't there any desktops on the market with same technology? I'm using an UPS for my desktop system, but I don't need it for the laptop. If the AC power drops, even for a moment, the laptop battery will kick in and sustain the machine. I just think that the same thing can be implemented for the desktop too. If I understood the OP correctly... ;-) Best, :-) Marko