jstarne1, robotmaker and my self were talking about regular lead acid and gel cell batteries for supplying power to a power supply unit. Later I said I liked lithium type batteries too. robotmaker said (more or less)that gels voltage falls off to much. I started thinking this morning that if you want a battery that doesn't let the voltage drop much then NICAD and NIMH batteries may be the way to go. All batteries as soon as you start to discharge them , the voltage will start to fall until you have completely discharged them. In this case the PSU would shut off because of low voltage. Lithium batteries are bad for this too. NICAD and NIMH are about the best that I know of for holding voltage till discharged. Thats why it's hard to build a good charger for them . Chargers use voltage to judge state of charge. I guess this is an advantage of NIMH and NICAD batteries.