ups battery

[NiHaoMike]

Converting from 120v to 12v and back to 120v is not very efficient. Build your own UPS from a power inverter and an ATX power supply with active PFC. Find the B+ rail (and its ground) in the inverter and connect it to the ATX power supply right after the input rectifier through a diode. Then add two 470uF or more 200v capacitors to the input circuit to make it a voltage doubler. (If 240v or 208v input, use only one 330uF or more 400v capacitor from B+ to B-.) Finally, keep the battery on float charge at 13.8v.

If you have an ATX power supply that accepts 12v from a wall wart (such as the PicoPSU), it is even easier. Same for most network equipment, which often operate from 12v. Just keep the battery at 13.8v with a float charger that outputs more than all the loads.

[The Atomic Ass]

Originally Posted by Christ

If I still had mine, I'd probably replace the (long since dead) batteries with lithium variants. I used to have a source for "dead" laptop batteries, which I could get for free, and repair for very little money. (It's often only one or two dead cells, not the whole battery.)

The UPS units I have used so far have been entirely incompatible with Lithium. They continuously charge the battery at 13+ volts, so as not to overcharge it, but so that the battery is always fully-charged.

[Christ]

Originally Posted by The Atomic Ass

The UPS units I have used so far have been entirely incompatible with Lithium. They continuously charge the battery at 13+ volts, so as not to overcharge it, but so that the battery is always fully-charged.

Good point.. I'd have had to use some sort of extra circuitry and a charge switch to turn them off, so they didn't kill the lithium cells.