Posted by gberry on December 4, 2006, 5:45 pm
I was checking the specific gravity in my deep cycle L-16 batteries
yesterday and about half of them had brown gray electrolyte. The
values for all of the cells ranged from 1.185 to 1.200.
Background info: This bank is about 4 years old and composed of 2
parallel strings of 8 L-16 deep cycle batteries which are charged
through 2 Solar Boost 3048's by 4 parallel strings of 6 Kyocera 120 PV
panels. Backup, topoff and equilization is performed with a 10 KW
diesel generator through 2 4048 Trace inverters at 30 amp per inverter.
Further info: During their life cycle the batteries have been through
many trials and tribulations corresponding with my learning. I started
as a rookie and now I believe that I am more informed. So at times the
batteries have been a tad low on water, they have been undercharged at
times, equilizations have been inconsistent and maybe not long enough.
I know that I have not been a good father, but I now know the error in
my ways. But, before I continue on I must know if the electrolyte
discoloration is an indication of an irreversible condition.
Posted by Charles Foot on December 4, 2006, 10:51 pm
Well, I guess we all murder at least one battery bank in our lives!
The Trojan datasheet quotes a voltage of 1.917 as being 90% discharged.
1.185 - 1.20 volts per cell is way beyond flat; more like dead.
Having two strings in parallel may well be a contributing factor to the
demise of the bank as a whole. However, there may be some life left, but
you are going to have to un-parallel the two strings, give each
individual string a good charging at around 30 amps (I wouldn't go too
much higher than this - overcharging may well cause even more damage)
and see what happens.
When it comes to replacement, my best advice would be: do not parallel
strings of batteries. Get a set of appropriately sized cells, series
them, and charge them strictly in conformance with the manufacturers
datasheet. Apply temperature compensation if at all possible.
I realise that all the battery manufacturers say that you may increase
capacity by paralleling batteries, but then they are in the business of
selling as many as possible, right? It simply is a no no.
Posted by _jj_ on December 4, 2006, 11:11 pm
Are we talking specific gravity ? or voltage ?
Posted by gberry on December 4, 2006, 11:26 pm
-- Show quoted text -
The values I quoted were specific gravity. The voltages at the time
ranged from 6.56 to 6.77 per battery. I have been charging through 2
inverters with 30 amp setpoints and I usually only run it for a couple
of hours. Batteries are usually bubbling at the end.
Regarding the charging of individual strings, do you think this is
possible from the inverters or would I need to physically disconnect
Wonder how long I should run the generator on each string. 30 amps,
320 amp/hr, maybe 50% discharged, 5 hrs sound good?
Posted by Harry Chickpea on December 4, 2006, 11:21 pm
These are now what can be considered experimental batteries. :-(
You can try some stuff and learn. What immediately comes to mind is
disconnecting them and trying a desulfator circuit on one, a simple
EDTA treatment on another, and a major EDTA treatment on a third,
complete with a wash-out with distilled water and a complete
replacement of the electrolyte.
IF the sulfation isn't too bad, the desulfator might do the job. If
it is a little worse, the adding of a tablespoon of EDTA might help
(but don't hold your breath). If it is major, yet there is still
sufficient PBO2 and supporting grid left, the rinse out will remove
most of the dead crap, and the new electrolyte will act on the
All of this should be tried out of doors, and with about a 2%
expectation of success.