UPS Backups

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Intimidator#3
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UPS Backups

Post by Intimidator#3 » Tue Mar 29, 2005 12:15 pm

I have a APC 500 ups battery back up, I have a new extra battery I want to install to double my backup time, Is this as easy as putting it in paralel with the other battery?? Or do I need to do something eles as well?<p>[ March 29, 2005: Message edited by: Intimidator#3 ]</p>

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jwax
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Re: UPS Backups

Post by jwax » Tue Mar 29, 2005 7:17 pm

A purist would say not to simply parallel them, one may discharge the other, etc.
I'd say go for it, in your application. As with any backup, check it occasionally.

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haklesup
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Re: UPS Backups

Post by haklesup » Wed Mar 30, 2005 5:51 am

Seems to me a few well placed diodes could prevent a bad cell from discharging a good one.<p>If you use two new batteries from the same lot, you will probably have no problem. If you pair a new one with an old one, you might be asking for trouble.<p>A thermal fuse taped to the battery side is a good and cheap insurance policy. A shorted battery of this capacity can surely cause a fire.

Intimidator#3
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Re: UPS Backups

Post by Intimidator#3 » Wed Mar 30, 2005 6:44 am

they where both bought new at the same time, I had only 1 that was bad an didnt replace my other ups's battery so they should be the same lot, one has just been used for the last 6 months though

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jollyrgr
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Re: UPS Backups

Post by jollyrgr » Thu Mar 31, 2005 8:46 am

Alpha UPS units use both series and parallel combinations to get the right voltage and extend run time. Some of the bigger APC units parallel two batteries as well. For instance they have two 12V 7.2AH batteries in series to get 24 volts. Then they parallel two of these series combinations to extend the run time. <p>The big "enterprise" class UPS use marine type batteries in series/parallel combinations as needed. Where I work we have two 100KVA units running our data center; both use series and parallel battery cabinets.<p>I can't see what haklesup has in mind. The UPS both charges and discharges the batteries. Putting a diode in series with the battery would prevent the battery from being recharged after it was used. Did I miss something?
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dacflyer
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Re: UPS Backups

Post by dacflyer » Fri Apr 01, 2005 10:06 am

i tried this too before.. replaced only the bad battery... BAD NEWS! a week later i had a melt down... somehting wasn't right.. and the other 3 batteries went bad quickly.. my UPS got really hot and the batterys swelled and cracked open.. new battery went bad too, it got too hot and melted.. so thats why they say never mix old batteries with new ones i guess..

Intimidator#3
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Re: UPS Backups

Post by Intimidator#3 » Fri Apr 01, 2005 10:09 am

mine is a single battery ups, i bought 2 batteries to replace batteries in both my usp's but only replaced the one that had a bad battery

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Chris Smith
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Re: UPS Backups

Post by Chris Smith » Fri Apr 01, 2005 10:26 am

What you can do is place a current limiter [light bulb or resistor] to charge the second battery at a much slower pace. <p>Your charge circuit may be limited to charging only one battery, and it may sense two batteries all wrong, either screwing up the battery [s] in question, or the charge circuit. <p>To get the full feed back when the power is off, can be achieved by the use of a Diode that blocks the Charge in, but allows a full discharge out. <p>This way when the batteries are used, and discharged, the charge cycle will only see one quick charge draw to the number one battery, and the second battery will have to trickle charge over the next day or two to get its current back, not placing any undue load or false signal to the charge circuit.

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