A couple power supply theorys

[BrianG]

Originally Posted by Jabe

I beleave that you can use your car battery charger, if you modify it. Or you could just make it charge battery, then hook your charger to that battery.
But why not, just modify your PC powersupply, you can find many instructions about it, i did that, used two pc powersupplys in parrel 350W+350W, well the other one was behind switch, so i could apply it, when needed, never needed it thought.

Just be aware that there is some "fighting" when using two seperate power supplies in parallel. The current isn't simply additive, it's more like 80% of PS1 + 80% of PS2. And if the voltages aren't very close, there will be more losses. Generally, it's best not to parallel power supplies, but to get a single one that has the total outout you need.

Originally Posted by Metallover

Is there a place I can get a really cheap used/salvaged pc power supply? I don't have any laying around.

The problem with "salvage" power supplies is that they are generally older models that don't have as high currents on the 12v rails as newer ones do.

The PS you get will be determined by your power needs. What is the max cell count and current you will charge? Better yet, what is the power limit of your charger? Just take that power, divide by 0.8 to account for typical charger efficiency, then divide that by the voltage. So if you have a charger with a 120w power limit, that's 150w. Divide that by 12v = 12.5A. And since you generally don't want to push anything to its max, I like to figure in another 25% for safety (and to account for some voltage drop under load), which would be ~16.5A.