[RE-wrenches] Sick pack

[Steve Higgins]

Bill,

Here is what I would do;


1.      Get the Specific Gravities of all the cells.   Record them on some short of sheet.   I've attached our troubleshooting form if you want to use that.

2.      Measure all of you unloaded voltages across the bank.

3.      Put about 1000 watts of load on the system and watch voltages on every battery every 15 mins for about an hour.


Getting the SG's will give us an idea of how sulfated the battery bank, in conjunction with loaded and unloaded voltages we can attempt to determine what batteries should be watched or removed.

Once you isolate the obvious bad cells you may be able to limit the amount of parallel strings and then start a charging regimen that will bring the older cells back up.

There two ways you can attempt to bring the batteries back from the deficit cycling that the end user has been subjecting them to...

One you can hammer away with frequent EQ (2.58vpc to 2.66vpc) charges, doing so will use up quite a bit of water and will probably cause some more damage (excessive heating) to the batteries.   If the batteries are recoverable then this will be the fastest way to bring them back.

Two, you can raise your Absorb voltages up a tad but to the 2.46 to 2.5vpc set points on the inverter, 2.5vpc on the controllers with LONG absorb times.   I would double your expected absorb times so the inverters/controllers hold the voltages up as long as you can... with most Solar controllers I'll also run the float voltage up around the 2.35vpc settings to keep the batteries gassing.
This is going to use more water than normal, but for the lack of a better term It will cook what sulphation that can be removed from the plates and keep the batteries relatively cool causing less positive plate shedding than EQ'ing.

Option one will take about 4-6 weeks before you really know how much of the battery bank you can save... Option Two will take 3-4 months with decent weather, but will be easier on the batteries...  It all depends on how much time you/or the customer has.

Just keep in mind with Surrette's we suggest a 2.36vpc to 2.5vpc absorb voltage based on temperature,  If using temp compensation you need to set the starting voltage at about 2.45vpc and adjust from there based on what your  SG checks look like.   If you notice your SG's rising, then you back off of voltage .2 to .4vdc...if you notice your SG's are falling then you add .2 to .4 vdc.   Your lighter users can see a bit lower absorb/bulk voltage than your heavier users.



Steve Higgins
Technical Services Manager
M: +1.206.790.5840
F: +1.902.597.8447
Surrette Battery Company
Exclusive manufacturer of
[cid:rolls1e2e7d]<http://www.rollsbattery.com>

From: re-wrenches-bounces at lists.re-wrenches.org [mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of frenergy
Sent: Wednesday, December 18, 2013 10:29 PM
To: 'RE-wrenches'
Subject: [RE-wrenches] Sick pack

Gentlemen and women,

        I have been called in to deal with a pack of 16 (4 strings of 4 for 24V), L-16s, 6 years old.  She is having to run her generator 2 times a day.  Here in N.E. CA. its been cold, mostly clear, little wind.  Her inputs are about 1 KW of PV, and small wind machine and of course a serious generator.  Cables and terminals looked clean, were tight.  The bulk setting on the Trace 4024 was 28.0 V for 2 hrs with RTS, however, she would manually turn off the generator soon after it reached 28V.  Recipe for suphation.

        Rather than getting into too much detail, here's my quandary.  When I fired up the generator, the input amps in each of the 4 strings were.... string #1:29A, 2:34 A, 3:25 A, 4: 13 A.  A survey of IR temps throughout the pack gave temps ranging from 63 to 92 degrees.  The highest temps were in the string pulling highest amps.  In trying to find shorted/failed and/or sulphated cells which data are most relevant?  Temps, amp draw during charge, disconnect strings from each other and check volts of each 6 volt batt?, active bubbling? ...all the above?

        I'm thinking I should have (1) checked the amp draw with batts under load/genny off in each string AND (2) check amps between strings with the pack at rest, no input or output.  I would love to EQ the pack but with a temp already in the 90's and uneven currents in the strings I don't want to risk too high of temp or worse, a runaway situation and fire. I'm thinking I'd like to yank a few bad batts and run on 3 strings and then carefully EQ.

I appreciate any insights.

Thanks in advance,

Bill
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