[Elecraft] K2 - Battery needs CPR

[Ingo Meyer, DK3RED]

Hello Tom,

I know I be late but hope not too late.

> The problem was that I went QRT for a year or so and left the battery 
> unattended and now it won't hold a charge.
...
> Any ideas would be appreciated.

Maybe your battery has a chance, but without guarantee. You say the battery don't hold the 
charge. So my question. Is there a significant charge current (minimum 100 mA) over some 
hours, if you put the SLA on 13.8 volts? If you now say "yes", put the SLA in the garbage, 
like also Don sayed. But if you say "no", it's possible to bring the SLA back to life.

In this case it's looks like the battery has a sulfat layer on the lead packages. This 
caused in a high internal resistance. You can measure after a charge 12 volt to 13.8 volts 
with a DMM, but the batterie don't hold the charge. The reason for it is, that the battery 
has not sucked any significant current during the charge process.

So try the following procedure: Put the SLA on a charger, which gives 13.8 volts AND a 
which has a current limiter of 100 mA or 200 mA or so. For controlling put a ampere meter 
in row with the battery. You will see for days or sometimes for 1 or 2 weeks no 
significant current flow. But if the sulfate layer at last is broken, the current flow 
jumps up. You know now, why the charger needs a limiter. After the charge procedure is 
solved, discharge the SLA again controlled until 10.5 volts and repeat the charge process 
with normal conditions.

I repeat it: There is no guarantee, but hope.
-- 
73/72 de Ingo, DK3RED - Don't forget: the fun is the power!
        www.qrp4fun.de - dk3red at qrp4fun.de