[RE-wrenches] Sick pack

Thu Dec 19 08:53:58 PST 2013

Bill,

This all sounds very typical of a neglected, deficit charged battery bank. More than likely (speaking from experience) the damage started a few years ago but due to the size of the bank, the customer was able to make 6 years as the sulfation grew. 

You can disconnect 1-2 strings and check the open circuit voltage of each battery. If the batteries are taken off charge, you might need to let them rest for a few hours or put a load on them before the test. I assumed you looked at each battery case sides to verify bulging and hardness. Another tell-tale sign is to look very closely at the positive posts: do you notice ANY lifting of ANY of the positive posts on ANY battery? If yes, don't waste your time trying to recover. Instead, spend that time educating the customer on how to make the new bank live 10-14 years. While I have had some success restoring mildly sulfated batteries over the years, I have zero success once the hardness has reached this level.

Most importantly, sell them a battery capacity meter if they don't have one.

The attached pictures shows a Trojan L16 that is only two years old. See the slight lifting of the post reference to the aluminum? The grey case L16 battery is 6 years old and has severe sulfation that started many years ago. Both customers did not know how to charge properly.

Larry

On Dec 18, 2013, at 11:28 PM, frenergy <frenergy at psln.com> wrote:

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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