Axilla
Finger, Finger
Premium,Mod
join:2001-03-26
Schofield, WI
clubs: | reply to sdgthy
Re: Home UPS powered by car battery: failed
In fact when you start getting into big "12v" batteries for backup power applications they recommend float charge voltages that can be all the way up to 14.5 volts depending on the battery type. |
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sdgthy
@optonline.net
| reply to CajunWon
Batteries that aren't meant for deep discharge will sulphate if they are deep discharged even once. Once they've begun to sulphate, it only gets worse.
A "12 volt" battery at 12 volts is quite low as fully charged they should be at about 13.8 volts. The UPS is gonna check the voltage to determine when the battery is getting discharged by checking the voltage. So although you have a higher capacity battery that could maintain current for longer at the lower voltage, the UPS has already decided the battery is nearly discharged and it's no longer safe to continue. |
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CajunWon
join:2005-12-30
Cary, NC
 ·ViaTalk
| reply to drjim
Thanks for the responses.
Starting battery, I had a spare for this test project. It's a marine grade battery.
AFAIK: Starting batteries are able to dump voltage faster as required as they tend to have more and thinner plates. But if high amps are not required then it shouldn't drop its' volt reading any quicker. Deep cycle & heavy duty batteries should be more difficult to sulfate the plates and therefore should recover from many near full discharges. But in my application, I should discharge the battery no more than once - 5 years, avg 5 2 hour black-outs/yr, & need no more than 1.7 amps with 1 amp avg.
I'm no EE so correct me where wrong. |
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drjim
Premium,MVM
join:2000-06-13
Torrance, CA
clubs:
| reply to CajunWon
Is this a Deep Cycle battery? If it's a "regular" starting battery, also called an SLI, it will have it's voltage drop faster under a constant load than a deep cycle battery will. It also won't last as long in this type of cyclic service as a deep cycle will.
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One man's Magic is another man's Engineering. |
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