[TriLUG] recommendations for UPS 12V batteries?

[Joseph Mack NA3T via TriLUG]

On Sat, 18 Apr 2020, Pete Soper via TriLUG wrote:

> Yars ago I instrumented a couple UPS devices to see how the behaved. I recall 
> one that was in the wrong county with respect to float voltage. Too low and 
> the electrodes accumulate sulphate and die. Too high and the water is 
> disassociated and driven past the pressure release as gas, leaving the 
> electrolyte short of ions. And the float voltage needs to be temperature 
> compensated.

I took out my two APC 700s, in which the batteries only last 2 years.

They have two batteries in series.

On float, one had the batteries at 14.0V and the other at 13.8V. I would accept 
anything between 13.8 and 14.4V. I was pleasantly surprised that both batteries 
within each UPS had the same voltage within 0.05V (If one goes low, then I 
assume the charger will hammer the other one.) The batteries weren't warm, so I 
assume the UPS is being nice to them.

So it would seem that these two APC UPS is doing the right thing as far as the 
batteries are concerned.

I then took out my unit in which the batteries lasted 10 years.

It has float V=55.0 (4 batteries in a bank. I didn't open it to measure each 
battery) = 13.75V/battery.

It would be interesting if a difference in float V of 0.1-0.2V/battery was 
making all the difference.

Joe

-- 
Joseph Mack NA3T EME(B,D), FM05lw North Carolina
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