Low electrolyte levels (was: More on battery management) [RE-wrenches [RE-wrenc

[Rob Harlan]

Windy and Company

We have been scratching our heads over a particular battery mystery:
It is an installation with eight new (now 4 months old) Surrette 530AH 6V
in 24V config.
We first were alerted that the Trimetric state of charge readings were
consistently sustantially over optimistic in relation to both voltage and
specific gravity data. This had resulted in maybe 3-4 weeks during which the
batteries stayed at pretty reduced charge levels.  The specific gravity
readings at this point showed a .020 spread between cells.
Since these were new batteries we suspected the Trimetric or the wiring.  We
proceeded to verify Trimetric settings as well as voltage and amperage
calibration (all OK), tighten all connections to the shunt, verify that all
amperage in and out was passing through the shunt, and insure that the owner
was bringing the batteries to 100% State of Charge ( based on 29.2V and 10
amps) every 5-10 days so the Trimetric has the opportunity to recalibrate
itself. We also installed a second Trimetric closer to the batteries to
provide comparative data (identical). At this point we don't think it is the
Trimetric.
Upon discovering the undercharged batteries with a 20 point sg spread we
assumed a sulfated condition and
initiated a generator-driven corrective equilization charge (bringing the sg
to 1.265 and holding the
batteries there for three  hours).  This resulted in a reduction of the cell
spread to
.013.
The next two and a half months consistently showed:
    1) Very inacurrate Trimetric state of charge readings (still
optimistic).
    2) A variance of 10 to 40 points in cell sg numbers.
During that 21/2 months we carried out two more equilization charges. The 40
pt spread has ocurred most recently.
SG readings are being taken with a refractometer which, by the way, we find
to be far easier to use than a hydrometer (order from
http://www.misco.com/traditional-hand-refractometer.html Glycol and Battery
Tester $135 part # 7084VP+)
The spread in cell readings do not reveal one outstandingly bad cell.
Unfortunately baseline specific gravity readings were not taken at
installation.  We have not been physically stirring the electrolyte before
taking refractometer readings. The other possibly pertinent information is
that the cells were slightly overfilled at installation with some degree
of electrolyte (probably not a lot lost during early charging cycles.

Can these symptoms be indicative of  a a low acid condition?   Wouldn't a
low acid condition prevent the sg readings from reaching 1.270?  How does
one determine electrolyte pH? Can a loss in electrolyte cause these
symptoms? Any other thoughts on this chronic wierdness?
Thanks in advance for this whole battery discussion and I look forward to
Windy's article.

Rob Harlan
Harlan Electric
NABCEP Certified




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