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Tinker Guru Joined: 07/11/2007 Location: AustraliaPosts: 1904
Posted: 04:13am 23 Sep 2012
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My battery bank here is 24V, made up from 2x 12V, 100Ah deep cycle batteries in series. There are 4 sets of these at the moment and they are connected to my new LIPO battery bank.
The LIPO takes much of the load now so the charge in the LA batteries gets only drained if an exceptional heavy demand from my 2 inverters is called.
Recently I have noticed on a routine battery terminal voltage measurement that one pair of LA batteries had a very uneven voltage. One was reading 14.5V while the other only showed 12.4V, taken while they were being charged and all other batteries were just about full and reading13.3-.4V each.
So the low battery actually never gets a full charge due to the unbalance, no good at all. I recently removed one LA battery pair as I thought one of them died of an old age (4 years) but I now think it suffered a similar fate.
What to do about it? Here is my solution and it appears to work, at least after one day of good charging @27V the battery terminal voltage was equal.
Its a simple shunt regulator, made from a heavy duty Zener, 5A diode, Transistor and a couple of power resistors. The shunt cuts in at about 13.5V so its heat sink gets barely warm during charging and there is no power drain overnight when the battery voltage settles to around 12.8V. The two leads have clip on battery connectors so the regulator can easily be moved to any other low reading LA battery.
Klaus
Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406
Posted: 01:27pm 23 Sep 2012
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That's another great idea Klaus !!
Cheers, Tony.
Tinker Guru Joined: 07/11/2007 Location: AustraliaPosts: 1904
Posted: 02:59am 24 Sep 2012
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Thanks Tony.
Batteries are expensive so looking after them p[ays in the long run.
Watch this space for an update on my LIPO battery equalizer coming up soon. The Mk I version was wearing out relays prematurely - and not for the obvious inrush current reason .
I think I'm hot on the trail of the cause, just needs some more testing to confirm.Klaus
Wombat Regular Member Joined: 27/05/2011 Location: AustraliaPosts: 72
Posted: 11:38pm 24 Sep 2012
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Hi Klaus.
I watch with great interest as I have many 12V batterys in my banks
that need watching. (Both 24 & 48V using 26 & 55Ah)
Happy you caught them before anything went south.
Russ
Tinker Guru Joined: 07/11/2007 Location: AustraliaPosts: 1904
Posted: 02:24am 25 Sep 2012
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Its still doing the job Russ, maybe a worthwhile gadget for your many batteries. I'll take it off that battery in a week or so to see if the recovery is a lasting affair.
I found all the parts for it in my bits'n pieces box so it did not cost anything.
Klaus
Downwind Guru Joined: 09/09/2009 Location: AustraliaPosts: 2333
Posted: 02:01pm 25 Sep 2012
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I would expect the battery is already shagged and the result will be short lived once the device is removed and the battery is cycled.
But worth a try for what its costed you.
In most cases its better to charge all the batteries in parallel for a period every so often to equilize them, although easier said then done in many cases.
Watching with interest, but my gut tells me its just CPR to a near to death battery.
Pete.Sometimes it just works
yahoo2 Guru Joined: 05/04/2011 Location: AustraliaPosts: 1166
Posted: 03:31pm 25 Sep 2012
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Maybe a poor connection or oxidised terminal in that bank. I see that a lot in parallel banks, particularly lightly loaded ones.
The symptoms for high resistance connections under load and a dodgy cell are pretty much the same. I'm confused, no wait... maybe I'm not...
Notice. New forum software under development. It's going to miss a few functions and look a bit ugly for a while, but I'm working on it full time now as the old forum was too unstable. Couple days, all good. If you notice any issues, please contact me.
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