OT-SLA Battery advice

[Dan Barker]

I have a bunch of 1,200 VA UPSs for my computers. These run two batteries
each. 3 of them have bad batteries. I ordered a case (6 units) of BB7-12 to
fix the bad ones.

The bad UPSs each appear to have one good battery and one bad battery. I
hate to take 3 apparently good batteries to the dump, but I hate to have my
computers crash during the 60 seconds it takes my generator to come on line.

Should I try to match up (How?) the used-good batteries with each other,
discard them, test them (How?) or just dump them in the "Battery" bucket
down at the local Recycling Center?

Dan / WG4S / K2 #2456

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[Don Brown-4]

Hi

I would try cycling them once or twice to assure they will meet specs.
Connect each one to a variable power supply set for about 13.8-14.0 volts
and let them charge until the current draw is just a few mA. Limit the
maximum current with the power supplies current limiter or install a 2-5 ohm
10 watt resistor in series with the power supply and keep the maximum charge
current below 1/3 of the amp hour capacity of the battery. For a 7 amp hour
battery that would be 2.1 amps. After charging the battery then discharge it
down to about 11 volts and see how long it takes. Multiply the time in hours
by the current to get the amp hour capacity. This should be somewhere around
the rating of the battery. You can use a old car headlight or a tail light
as a load to discharge the battery. Do not allow the battery to discharge
below 10 volts or you may damage it. A heavy load like a headlight will not
give quite as much capacity as a lighter load like a tail light but you
should get a feel for the condition of the battery with these tests. If the
battery voltage falls off quickly under load or it will not take a charge
then the battery is most likely shot and should be recycled.

Don Brown
KD5NDB


----- Original Message -----
From: "Dan Barker" <[hidden email]>
To: "Elecraft" <[hidden email]>
Sent: Friday, February 03, 2006 12:44 PM
Subject: [Elecraft] OT-SLA Battery advice

> I have a bunch of 1,200 VA UPSs for my computers. These run two batteries
> each. 3 of them have bad batteries. I ordered a case (6 units) of BB7-12
> to
> fix the bad ones.
>
> The bad UPSs each appear to have one good battery and one bad battery. I
> hate to take 3 apparently good batteries to the dump, but I hate to have
> my
> computers crash during the 60 seconds it takes my generator to come on
> line.
>
> Should I try to match up (How?) the used-good batteries with each other,
> discard them, test them (How?) or just dump them in the "Battery" bucket
> down at the local Recycling Center?
>
> Dan / WG4S / K2 #2456
>

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