UPS battery voltage question..

[Nothing40]

Hey guys,

 I've got a Best 400W UPS running my 2 PC's/monitor,and I've replaced the internal batteries (2x 12V 6.5AH SLA's,they were dead when I got it for $5.)

So,I've run heavy cables out to a pair of car batteries I had around.(not deep-cycles,but for the occasional UPS duty,they should be fine.)

Everything seems to work just fine,but I have a question about the battery float voltage,which is ~26.80V (about 13.40V per battery)

Is this too high for flooded lead-acid batts?

The batteries don't seem to use alot of water or anything,I check them every couple months,and add a few CC's to each cell to top them off,if needed.

Just curious if I should open it up again,and see if I can find a voltage adjustment trimmer.

Thanks Guys!  Patrick.

[asheets]

I think that your float might be a touch low...  don't car batteries need a float of at least 13.8vdc?

[Nando]

13.40 volt is the minimum Float voltage for those batteries in the UPS that may be used once in a while.

If You replaced them with heavier car batteries and, as well, using the batteries constantly, it would be best to set the float voltage around 13.6 to 13.8 volts,

I do not know if can change the float voltage to that Best UPS.

Nando

[Nothing40]

Hum,

I guess I'll open it up sometime soon and see if there's a trimmer to adjust the float voltage.We'll see..

Thanks guys!

[Chagrin]

Thought I might emphasize the point that SLA batteries tend to have a lower float voltage than car batteries.

[AbyssUnderground]

My UPS floats on 13.4-13.8v. It pulses between the two values continuously when charged. I was supprised they were looking after their battery so well.

Im currently floating my main battery (17.2Ah SLA) on 13.91v from a 13.8v regulated PSU (not so regulated afterall!) and about 20mA. Its been on for 18 hours now. Just giving it a good absorb charge. It seems to work well for me so the UPS should do great.

[dalibor]

for lead - acids cells floating level should be around 2,23 volts per cell on 20 degrees celsius. this is general rule for standing batteries, but for the cars it could be higher for few percents.

so: 2,23 X 6 cells = 13,38 volts. i guess you are doing fine with yours.

when we boost them, we load them to 2,4 volts per cell.

after capacity testing we charge them to almost 2,65 to 2,7 volts maximum. but this is only after deep charging ( 1,8 volts per cell with 10 hours 1/10 of nominal current). capacity you have on their walls is that type of data - for 10 hours discharge period with 1/10 of nominal current.

hope this was useful :-)