Instructables

Make your computer UPS last for hours instead of minutes

Step 8: A word of caution

I learned this the hard way.. it cost me a UPS, and nearly a fire.

The transformer in these UPS's are cheap. They are not designed to be run at 100% capacity for extended periods of time (such as what you will be capable of using this size battery) When I ran my UPS's at 300 watts for more than 30 minutes, the transformer melted through the case. When I pulled out my infrared thermometer it read nearly 400 degrees F!!

I had to redesign my system. I chose two UPS's that were rated at 600 watts each, but used 24 volts (2 twelve volt batteries in series). Under my new setup, I have over four hours of backup capacity as I have two car batteries.
 
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Great plan only I use gel cell batteries so have no issues with adding water or any other thing. Maintenance free only way to go. Do you have any issues with over charge on the battery? My UPS doesn't like any battery voltage above 13 volts but yet puts out 13.5 to charge the battery. My battery levels off at 13.4 volts and the UPS when turned on goes into fault mode and blinks red light and beeps. Once I lower the voltage at the battery down to 13 volts or less then all is good. Any ideas??
garfnodie2 years ago
I have a UPS that I'm needing to replace the battery on, I'm thinking of getting two, or maybe even three replacement batteries for it, ones that are designed for this particular UPS (12v, 4AH, 20HR is printed on the existing battery). Can I hook them in series without any issues? I'm actually not even going to be using it for a computer, but for a set of decent speakers with my ipod hooked up and an alarm clock so that they all continue to work for hours even if the power goes out during the nasty storms we can get here in the midwest. Three batteries may be overkill, but they're pretty cheap and I want many hours of power, and these aren't high current devices, so I'm hoping it'll work just fine. Will the charger in the UPS be able to charge all three batteries just fine, even if it take a few days, that's fine.
ben.mcfadden (author)  garfnodie2 years ago
You can put the batteries in Parallel, but NOT in Series. Otherwise, that sounds perfectly reasonable. Make sure you don't get a buzz in your audio equipment on the inverter before you spend the money on the batteries. I've had less than stellar experience with power inverters and audio equipment.
hey ben did u connected two UPS's to a single battery. I am worried about the charing of the battery cos i was told that UPS cannot charge a Car battery. do u have any charging issues in this instructables. i am waiting for ur reply.
also i have 3 PCs two with CRTs and one with 15inchs TFT how much power do i need for the whole, i am currently using 2 USPs, 1 550 VA and other is 500 Va with which i am using one to power Just monitors and others to power TFT and 3 CPS. and its working fine. (I think) i am fed up of the backup its less that 5 minutes.
please guide me.
Thanks
Gagan
India
nothing will happen dear friends. what do u think about almost everyone in the world is using inverter systems (dont forget with battries) inside there homes or in the basements of there homes. what will u think about it.
drzcyy4 years ago
hydrogen or oxygen is not toxic by themself, besides the explosive nature when combined. However, charging and discharging lead-acid batteries indoors will release microscopic sulphuric acid droplets due to bubbling (or gassing) of the acid in the cells (try leaving a piece of paper over the battery for sometime, the paper will turn color over the ventilation holes!).This has been known to cause damage to lungs, as well as oxidation of metal parts in the vicinity. The way to overcome this is to cover the ventilation holes of the cells with steel/iron (but not stainless steel ok) wool used for cleaning pots and pans in the kitchen.The wool will be oxidised first, rendering the released sulphuric acid harmless.
ben.mcfadden (author)  drzcyy4 years ago
Wouldn't air current solve this problem? Like, perhaps, and air conditioner? I'm in Arizona, so the unit is on pretty much 24/7. I don't think you could get much more air circulation.
BretteJaro4 years ago
The main problem you will find is the batteries will be damaged pretty quickly (6-12 months) because the float voltage of the SLA batteries is higher than that of the flooded cell batteries. You will need to keep a close eye on the electrolyte level because it will drop pretty quickly. Another byproduct is higher standby power consumption because the UPS will keep trying to charge the batteries, but in reality, will just be disassociating the water, or gassing.
If you have to add water to a flooded lead acid battery, always use distilled water. Anything else will contain minerals or contaminants and reduce the life of the battery substantially!
loki03474 years ago
Actually I've seen a single car battery have it's excess hydrogen explode from the sparks thrown off by detaching a charger under load...
bubba0075 years ago
Play it safe:
Remember charging a car battery indoors can release harmful (toxic) gas fumes. Be careful where you put the batteries