[Elecraft] OT-SLA Battery advice

[Don Brown]

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" <dbarker at visioncomm.net>
To: "Elecraft" <elecraft at mailman.qth.net>
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
>