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For what would appear common sense to me, but perhaps not to all, I have all of my computers on UPS battery backups. After getting frustrated when the power flickered one day, I immediately went out and purchased a UPS. Well, shortly after, the power went out for longer than the battery could keep my computer afloat. I needed a better solution!
I wanted my UPS to be able to last for at least 60 minutes in a power outage. I needed more power! My solution: Car batteries.
Materials:
UPS that is rated at least double what you plan to draw (see step 8 to understand why).
Wire (12 awg or larger; two different colors)
Solder
Heat shrink tubing
Car battery with terminals on the top
Adapters to go from the car battery terminals to threaded rod.
Wing nuts the same size as this threaded rod
Wire crimp terminals that will fit over the threaded rod.
Plastic case for your car battery
Inline Fuse holder (radio shack)
30 amp fuse for holder (any auto store)
Tools:
Screwdrivers
Wire cutters
Wire strippers
Soldering iron
Scissors (optional)
heat gun or alternative
Drill
Drill bits
I wanted my UPS to be able to last for at least 60 minutes in a power outage. I needed more power! My solution: Car batteries.
Materials:
UPS that is rated at least double what you plan to draw (see step 8 to understand why).
Wire (12 awg or larger; two different colors)
Solder
Heat shrink tubing
Car battery with terminals on the top
Adapters to go from the car battery terminals to threaded rod.
Wing nuts the same size as this threaded rod
Wire crimp terminals that will fit over the threaded rod.
Plastic case for your car battery
Inline Fuse holder (radio shack)
30 amp fuse for holder (any auto store)
Tools:
Screwdrivers
Wire cutters
Wire strippers
Soldering iron
Scissors (optional)
heat gun or alternative
Drill
Drill bits
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I was trying to power two computers (desktop and file server), and two flat panel monitors. My total power consumption was roughly 500 watts peak. (yikes!) Currently I was running on two 300 watt UPS's (NOTE: VA is not equal to WATTS. Find the WATT rating) with one computer and one monitor on each. Even though the two monitors were hooked up to the same computer, I needed to distribute my power load more evenly to get longer battery life out of my petty UPS's.
CAUTION:
I discovered the hard way after nearly starting a fire and destroying a UPS that you need one that is rated at at least twice the wattage you are consuming. They can't handle being run for longer than a few minutes at this rating, but the batteries die before it's a problem normally.
So I now knew I needed 500 watts, and I wanted 60 minutes of power.. that means:
P / V = I
500 watts / 120 volts = 4.16 ampere hours (at 120 volts)
UPS batteries are usually 12 volts, but some are wired with two batteries in series. Check yours out first to make sure you won't need two car batteries.
So, assuming 12 volts, that means that, after adjusting for the voltage differences, I need a battery with at least 41.6 ampere hours. (yeah, I know there's inefficiencies in the UPS, but lets keep math easy)
CAUTION:
I discovered the hard way after nearly starting a fire and destroying a UPS that you need one that is rated at at least twice the wattage you are consuming. They can't handle being run for longer than a few minutes at this rating, but the batteries die before it's a problem normally.
So I now knew I needed 500 watts, and I wanted 60 minutes of power.. that means:
P / V = I
500 watts / 120 volts = 4.16 ampere hours (at 120 volts)
UPS batteries are usually 12 volts, but some are wired with two batteries in series. Check yours out first to make sure you won't need two car batteries.
So, assuming 12 volts, that means that, after adjusting for the voltage differences, I need a battery with at least 41.6 ampere hours. (yeah, I know there's inefficiencies in the UPS, but lets keep math easy)
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I recently had the idea of converting my APC Back-UPS BK300C into a handy portable 120VAC power station, by replacing the internal OEM 7amp-hr battery with an external 36amp-hr deep-cycle battery pack, adding a carrying handle on top, and converting the wired-in 120VAC power cord to a 120VAC chassis socket with a removable 120VAC power cord.
But I soon discovered the the OEM internal battery is intentionally in a self-sacrificing mode during power outages: The internal circuit sounds a continuous alarm when the internal battery discharges down to 11.4 volts -and will continue to discharge until the battery is dead. Any 12 volt lead-acid battery that discharges down to 11.0 volts is generally considered dead anyway, and should be replaced with a new battery.
Also, the unit is not fan cooled, so someone's suggestion to run the unit at no more than half the rated output wattage (when in extended emergency backup mode) is sound advice. But the large internal transformer is mounted to the outside steel case, which still functions as an effective heat sink.
After some deliberation, I simply decided to put the perfectly functioning unit back to together again, with no modifications done, and left it on the street curb with a "FREE & WORKS" sign, where it vanished after a couple of hours.
It was a pity, as the internal circuitry is both efficient and smart, discharging the 12VDC battery in direct proportion to the 120VAC load. And the two heavy-duty 120VAC electrical outlets would have been more than welcome in the field.
I'll just have to pick up another Vector iMobile Microslim Power Inverter VEC414S instead, for two 120VAC outlets in the field.
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
To determine how much power you need, I recommend using the Kill-A-Watt meter (http://www.thinkgeek.com/gadgets/travelpower/7657/) to determine how much power each item draws. Be sure to measure VA, as that's what most UPS's are rated in, although Watts are useful too.
Remember, if you are going to make your UPS system last for more than the time a stock battery will last, be sure you are putting less than 50% of their rated capacity on each UPS.
1. Its the voltage that tells the charger how well its doing. For standard Lead acid batteries they are full when they read between about 13.8 and 14.7 volts.
2. Calcium-infused batteries apparently are full at a higher voltage so you need to be aware of that - you might be over or under charging.
3. I think that so long as you are using the same type of battery with the same charging needs as the original one it should work, it will just might take longer to top up.
4. It won't be ideal but should get you there!
The main caution with ANY automotive type replacement battery is that hydrogen gas is produced when charging (only small amounts when trickle charging like this) and they have liquid acid inside. Make sure they don't get tipped!!
Bear in mind there are NO SMOKERS in my house/office - EVER, but truly - using a UPS to process battery power into 120VAC is a great idea as is boosting the run-time of your UPSs.
I add only one warning which has been said here before repeatedly:
DO NOT OVERLOAD YOUR UPS !
The bigger battery is for stand-alone power or added runtime - NOT for supporting a load beyond about 60-70% of the UPS's rated capacity.
If you can find them:
My all time favorites are the really old, metal-cased APC units connected with solid house wire to lawn tractor batteries.
The hydrogen gas released by any lead/acid battery has a very obvious odor and is unlike anything else -and I have never, never, never had any problem doing this indoors.
One important point IMO:
Since there is always the possibility for leakage I recommend ALWAYS placing any such battery or batteries into a plastic tub like a dollar store dishpan to catch any dirt or possible leakage if anything ever needs catching.
Solar enthusiasts:
If you seek out your local PC recycling freak who has connections with places that recycle servers and big UPSs you can use those super-high quality inverters with your batteries and save a bundle instead of branded solar-only inverters.
Last word of my opinion on this matter -> this IS the Instructables site for DIY'ers and if anyone who reads these is too afraid to experiment and learn by doing then this I would recommend ONLY buying ready-made, UL approved devices and leaving the DIY to enthusiastic DIY'ers.
Happy DIY'ing !
Remember charging a car battery indoors can release harmful (toxic) gas fumes. Be careful where you put the batteries
Oxygen is only explosive in high concentrations, which is to say it has to be very pure to do so. Chances are, it is not going to have the correct mix for it to be combustible at any level that you could create with just 2 batteries.
Combined with the fact that it only produces these gases when it is charging and not discharging....... You should be pretty safe. Just don't keep it all contained in a super enclosed space and you should be fine.