[RE-wrenches] High specific gravity

[Howie Michaelson]

Mac,

In my experience, cells that read 1.0 rarely if ever recover to a usable
state.  I've also seen abnormally high SG readdings (1.31+) in battery
banks that are over charged, which may be the case here.  You stated the
set points for absorb and equalize, but was this just for the VFX or for
the Charge Controllers (solar and wind) as well.  I've also seen very high
SG readings in cells near the dead cells (1.0), which I have interpreted
as being caused by the dead cells not passing the charge very well, but I
don't really understand the physics of the phenomenon.  If after another
equalize cycle, the dead cells don't change, you could try taking them out
and bench charge those batteries individually.  Depending on the age of
the batteries, particularly since they are Interstates, I would tend to
not spin my wheels too much trying to recover them, and instead counsel a
full bank replacement (not usually a happy conversation). I usually argue
that replacement is money better spent.

Good Luck,
Howie
-- 
Howie Michaelson
NABCEP Certified PV Installation Professional™

Catamount Solar, LLC
Renewable Energy Systems Sales and Service
VT Solar Electric & Hot Water Incentive Partner
http://www.CatamountSolar.com
802-272-0004


On Tue, August 12, 2014 11:01 pm, Mac Lewis wrote:
> Thanks for the responses everyone.  I never considered that acid may have
> been added.  I'll have to press him a little bit on that.  He's definitely
> "old school" so I wouldn't be surprised if he tried this.  Dan, I
> calibrated the refractometer, so I have confidence in its readings.  When
> I
> say all over the place, we had 3 cells of specific gravity of 1.0, the
> rest
> ranged from 1.24-1.33.  He is going to equalize again, but we will see if
> he added acid.
>
> Thanks again.
>
>
> On Tue, Aug 12, 2014 at 8:13 PM, William Miller <william at millersolar.com>
> wrote:
>
>> Mac:
>>
>> Someone has added acid to the cells. I've had the same experience and
>> found out the truth later on.
>>
>> William
>>
>> Miller Solar
>>
>> On Aug 12, 2014, at 6:54 PM, Mac Lewis <maclewis1 at gmail.com> wrote:
>>
>> Hello wrenches,
>>
>> I just went on a service call for a new client.  He had a bank of 4 year
>> old Interstate L16HCL batteries, 2 strings of 8, 48V system, 840Ahr.  We
>> went through the batteries and got specific gravity on all of the cells
>> post-equalization.  I was a bit surprised to see some very high numbers
>> ie
>> over 1.32 for the specific gravities (higher than my refractometer
>> goes).
>>  The specific gravities were all over the place, but I haven't seen
>> numbers
>> this high.  I don't have a great explanation.  He has a stacked 3648 VFX
>> Outback system, and the set-points were 58.8V Absorb for 2 hours, and
>> 62V
>> Equalize for 2 hours.  He has a decent amount of solar (about 3400W) and
>> a
>> 1000W wind generator.
>>
>> Any ideas why the specific gravity is so high on some cells?  Also, is
>> there anything wrong with having SG this high, post-equalization?  For
>> this
>> very standard battery, what settings do you go with (Bulk, Absorb,
>> Float,
>> Eq, and times for Abs and Equalization).
>>
>> Thanks in advance
>>
>>
>>
>> --
>>
>>
>>
>> Mac
>>
>>
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>
>
> --
>
>
>
> Mac Lewis
>
> *"Yo solo sé que no sé nada." -Sócrates*
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