[RE-wrenches] High specific gravity

Fri Aug 15 09:14:51 PDT 2014

Hey guys, just thought that I'd chime in here if you don't mind.

High SG's are a result of a few things...

1. The most common... Adding acid or electrolyte
2. Overcharging, or too long of
3. Overheating.. During the charge cycle if you have overheating cells and you get over 120 F ballpark (most batts these are different ceilings).  During this high temp period the active material on the plates starts to dissolve into the electrolyte and will increase the acid content in the battery.
4. Problematic Cells.  If you have cells that are dead, the good cells can sometimes "absorb" the extra voltage from the charge process.   This will cause a rise in SG's.  A couple weeks at normal charge voltages and good cells the SG's should fall..  If they don't then the problem is either #1, or #3.

Steve Higgins
Technical Services Manager
M: +1.206.790.5840
F: +1.902.597.8447
Surrette Battery Company
Exclusive manufacturer of
[cid:rollsb055cb]<http://www.rollsbattery.com>

From: RE-wrenches [mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of jay peltz
Sent: Tuesday, August 12, 2014 7:47 PM
To: RE-wrenches
Subject: Re: [RE-wrenches] High specific gravity

HI Dan,

I would respectfully disagree that hydrometers are always accurate.

However  both can be easily tested with distilled water, should be 1.0

Jay

Peltz Power

On Aug 12, 2014, at 7:40 PM, Dan Fink wrote:

Brian;
That was to be my next response to Mac after he checked the refractometer against the the old fashioned float. A customer saying "My grapnpappy said ya gotta add acid, not water, and ya better not put them batteries on concrete floors, all the power drains out......" ---it could happen
Hopefully that's not the case, but in any case it's probably fixable. I don't like the SG readings "all over the place" part. Sounds to me like the refractometer got damaged.....and such damage would not neccessarily be visible.

The float will always be true, and if ya drop it, the glass breaks. ;-)

Dan Fink
Buckville Energy
Otherpower
NABCEP / IREC / ISPQ accredited Continuing Education Providers
970.672.4342

On Tue, Aug 12, 2014 at 8:31 PM, Brian Teitelbaum <bteitelbaum at aeesolar.com<mailto:bteitelbaum at aeesolar.com>> wrote:
Mac,

Sounds to me that "someone" (ahem...) added some sulfuric acid to the cells instead of plain distilled water.

Either that or there is some sort of contamination in there that is raising the density or "weight" of the fluid beyond just what the proper amount of acid would do. "Specific gravity" is just a measurement of how heavy the fluid is compared to plain water (specific gravity of 1.00). Sulfuric acid is heavier than water, so when mixed will increase the density and raise the weight of the fluid. Temperature effects the measurement too of course.

If it turns out that acid was added, you can balance them out by removing some of the electrolyte from the high cells and replacing it with distilled water. It would be a process of trial and error to get them all the same. Remove a little, add some water, equalize again, measure S.P. and repeat as needed.

Leaving the electrolyte too strong will shorten the battery life, although maybe not enough to go through this ritual.

Brian Teitelbaum
AEE Solar

From: RE-wrenches [mailto:re-wrenches-bounces at lists.re-wrenches.org<mailto:re-wrenches-bounces at lists.re-wrenches.org>] On Behalf Of Mac Lewis
Sent: Tuesday, August 12, 2014 6:55 PM
To: RE-wrenches
Subject: [RE-wrenches] High specific gravity

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 Lewis

"Yo solo sé que no sé nada." -Sócrates

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