Tuesday, December 27, 2011

Trouble at t'mill

[Retrospective posting again - It's actually February 2012]

Hmmm... Lead acid batteries... You gotta love 'em.  Not.

The new setup initially seemed fine, but I've noticed a nasty gassy smell when charging on sunny days.  The block balancers are working fine and the two 12V halves of the banks are in balance, but there's some venting of gas under charge somewhere.  Quite a lot of gas - as I had to open all the doors and windows to clear my nausea.

Not good behaviour for a set of "sealed" batteries.

With the Ritar batteries replacing the gel ones, I had increased the absorption charge Voltage to 2.375Vpc (14.25V / 28.50V at 25C with 4mV per degree C compensation).  The Marathon bank is still attached and doesn't like to go up to much more than this but the Ritar blocks actually specify a higher Voltage of up to 2.433Vpc (14.60V at 25C).  So it's unlikely that the Ritars are the problem.

So I reduced the absorption charge Voltage down a bit to 14.20V and set the temperature compensation slope to stop at 17C.  That way the compensated Voltage never goes above 14.40V.  The absolute limit for the Marathons.  Not normally a problem but lately it has been 16C in the mornings by the battery bank (the patio door double glazing isn't what it could be...).

Still no good. Maybe the Marathons can't handle higher than gel Voltage at all.  So I threw the breaker on the Marathons and ran with the new Ritar battery bank only to see if that would isolate the problem (to the Marathons).

No good.  After a few days of charging and chopping and changing the Marathons around I discovered that it's one or both of the new Ritar batteries that are making the gas.  They seem to be in balance electrically and deliver the power ok and charge ok but I'm getting poisoned while working downstairs!

I even resorted to ripping out the Marathons and sticking them in the garage outside to totally eliminate the possibility that they were gassing while idle in the room.

So now I have had to swap over again.  The new Ritars are definitely dodgy in some way.  Even quite gentle charging above float level causes a degree of noxious behaviour.

The Ritars are now the ones outside in the garden and I brought the Marathons back in but discovered that one of the 6 packs is nearly dead.  It doesn't accept charge very well at all.  The fact that it was in parallel with all the others and they used active balancing had masked the fact that one of the packs was dead.

So now I'm down to just two pairs of the Marathons that are probably quite long in the tooth and my new batteries are pants...

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