Long battery story (was Concordes) [RE-wrenches]

[Joel Davidson]

Travis, Did you take before and after hydrometer readings?


"Travis Creswell, Ozark Solar" wrote:

>
> Warning to all of those who don't install battery based systems: Long
> battery story follows.
>
> I recently found 2 of the big 12v/255 ah batteries at less the 1 volt each.
> An inverter had failed locking its cooling fans on.  No other charging
> source for the batteries and they were left like that for months before I
> was called.  I brought them back to my shop and carefully took them through
> some cycles.  At first, just a few amps would immediately take them past 15
> volts and they started gassing a little bit.  I put one of them on test a
> system in my shop with about 8 amps of PV and Solar Boost 50 and TM2020.  It
> was a sunny day and the SB50 immediately took the voltage past 15 and
> dropped into float.  The battery stayed at float with just over an amp.
> Over the next few hours I watched and to my surprise the SB50 kept cranking
> the amps up to keep the battery at float.  Maybe a .1 v every 5 minutes.
> Sun appeared to be constant so what was happening was as each mAh went into
> the battery it was coming back to life.  Periodically I would disconnect the
> PV then reconnect it.  As expected SB50 would go into bulk hitting the
> battery with all the 8 amps and the would shoot up to over 15 so the SB50
> went into float again.
>
> After nearly a day it couldn't keep the battery at float with 8 amps.  Then
> I hooked the battery up to a 30 amp/3 stage charger and saw that it took all
> 30 amps to get the battery to bulk.  Took the battery through a few deep
> discharge and charge cycles and then did a capacity test using an inverter,
> incandescent lights and a TM2020.  At a ~C/20 discharge rate I was getting
> about 175 ah hours out of the battery cutting the test off at 11.0 volts.  I
> think most manufacturers rate the capacity at a cut off of 10.5 volts (1.75
> vpc).  Remember I found it at less than 1 volt.  The other battery responded
> the same way.  These batteries had been in grid back up application in float
> mode and had probably seen less than 20 50% DOD cycles in the 3 years they
> had been installed.  In my shop I did use the 4 amp 12 volt VDC Electronics
> battery desulphator on them.  If I had of been thinking I would have not
> used the desulphator on one and could have done the AH test to see if it
> actually does anything.
>
> The above results might no have anything to do with them being Concordes.  I
> also took 4 practically new Trojan T105's through the same procedure
> recently.  They had been left on a RV and had been drawn down to less than 1
> volt each and left like that for months.  They were less than a year old and
> probably had less the 5 cycles.  They've come back to life just fine and
> their AH capacity appears to be just over 160 amp hours @ C/20.
>
> Travis Creswell
> Ozark Energy Services

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