Just wanted to share my upgrade of a UPS (uninterruptible power supply) I will give credit where its due, this project was inspired by this UPS I liked this guys idea, however he was using the wrong batteries that will kill you if they are charged indoors (car batteries) not to mention they are starting batteries and not for deep cycle use. So heres what i got. I purchase four items: 1. APC BK500 = $2.50 2. APC BK200= $2.50 3. UNIVERSAL D5722 SEALED LEAD ACID BATTERIES (12V; 35 AH; UB12350) = $50.32 4. UNIVERSAL D5722 SEALED LEAD ACID BATTERIES (12V; 35 AH; UB12350)= $50.32 5. Shipping for batteries= $33.00 Grand total: $138.64 (this is the price of one brand new unit folks) + beer money I bought the UPS from a computer salvage store in my local area, the guy told me 5 bucks for both, he advised they were old, untested and probably had dead batteries. I bought them anyway. Sure enough the small 12v 7amp hour batteries were fried, so i went online to find replacements. Well turns out these suckers can get pricey. So instead of buying the 12v 7amp hour battery i bought much bigger ones. I bought two 12v 35amp batteries from electOtronics.com These batteries are generally used for wheel chairs and emergency lighting. They are SLA deep cycle batteries. so they dont give off fumes while charging, which makes them perfect for this application Once the batteries arrived, I lengthened the wires from the UPS to the batteries and connected them. I have found that these batteries fit nicely inside a 50 cal ammo box. This setup is not apart of my alt.energy setup and is soley for my computer and monitor. The 7amp hour battery's were good for about 10mins of backup, So far I have tested these at 45 mins. I will do some longer testing after my kill-a-watt meter arrives (I am not sure on the watts my compuer and large monitor require) I plan on installing a couple of small computer fans in the UPS case to allow for proper cooling as these units were not designed to run for longer that 10 minutes. By all means this is not a comprehensive guide but i feel it is a good FYI. I have since found these batteries on overstock.com for $60ish and the shipping is like 3 bucks.