[RE-wrenches] Surrette Battery Question

Fri Aug 1 22:18:15 PDT 2008

When i went to an SEI class at the Trojan factory one of the points
mentioned was that the best way to get the lowest cost per watt from the
battery bank
(T-105's were at the time the lowest) was to cycle them to 80% discharge
then fill them all the way up. Not feasible in an off grid system at all.
We get more years life by just taking off the top 20 - 25% and returning it
daily.

My battery distributor says that an industrial deep cycle battery needs to
be cycled occasionaly to prevent them developing a "memory" so to speak.
I recommend to my customers that they occasionally let them run down to 50
-60% DOD and fill them back up with an EQ charge to stir up the electrolyte
so you can get an accurate reading with a hydrometer.
Stratification will throw off the gravity readings unless they get stirred
up occasionally.
I have pulled apart batteries that did not get an EQ and found the bottom of
the plates wore out and the top still looking reasonably good. That is from
the acid being a lot stronger at the bottom than the top and just working on
the bottom of the plates in the battery. This is not a "fun" project and
usually results in some trashed clothes, rubber suit or not.

I have 80 volt battery packs that get cycled to 70-80% DOD daily for 5
months a year then sit for 7 months with just a couple freshening charges
and last 6 - 7 years till wore out, some of these are hi acid batteries that
are in the specific gravity range or 1.325 or more when fully charged
instead of the usual 1.265 -1.270 that we are used to seeing.

I am not a battery "expert" I just have several big banks that I maintain
and have formed some opinions over the last 15 or so years.
I have also experienced wearing out a set of L-16's by hitting the end of
their cycle life in just over a year. It was way too small a battery bank
and got cycled fully almost daily hitting it's cycle life limit far
sooner than a larger bank would have if treated well.

Good night,
Bob

On Sat, Aug 2, 2008 at 12:01 AM, jay peltz <jay at asis.com> wrote:

> Hi Robert,
> When you mention cycling batteries, are you saying that batteries in a
> offgrid system that are being cycled 15-25% a day should be cycled even
> deeper than that?
>
> Thanks,
>
> jay
> peltz power
>  On Aug 1, 2008, at 8:36 PM, robert ellison wrote:
>
>  A couple things that I haver noticed in the past, sometimes batteries
> like to be cycled, shut off the controllers and run them down, then charge
> them up fully and then give them an eq charge till it comes up the peak
> voltage and hold it there as it (sometimes) slowly rises. Any of these
> thoughts are superseded by Jamie if he has any thoughts.
>
> Also, if you have not given them an eq in a while it might take longer than
> the available solar time has to get them to the top and hold them there..
> Have the controllers settings changed?
>
> Bob
> On Fri, Aug 1, 2008 at 10:18 PM, Allan Sindelar <
> allan at positiveenergysolar.com> wrote:
>
>>  Wrenches,
>> In late 2003 we installed a 24V set of Rolls-Surrette 4-KS-21PS 6V 1104
>> A/hr batteries in the off-grid system of a long-time client. The client's
>> system had a democracy array of around 800 watts of tracked PV. In early
>> 2005 we added 1,280 watts of additional PV, and the client hasn't run the
>> generator since; the system rarely drops below 80% and fills to 100% most
>> days in sunny New Mexico. Batteries are located in a basement, so
>> temperatures stay relatively constant, although it will vary slightly
>> seasonally. MX60 controller is temperature compensated, with 29.6 VDC bulk
>> and 31.4 VDC EQ set points.
>>
>> The problem is that the client reports being unable to achieve previous EQ
>> voltages, and this inability appears to be a new development. The system is
>> otherwise performing well. As the client is sharp and pays close attention
>> to the system's operation, I'm not ready to blame user ignorance (with one
>> possible exception; read on). This may be an issue of seasonally warm
>> temperatures, but I'm not sure this would explain the full 0.4 VDC reduction
>> in voltage. I told him that I would post his problem to this list, and also
>> request advice from Surrette Battery.
>>
>> Here is the client's description of the symptoms:
>> I'm concerned that I am unable to equalize batteries at this time.  Up
>> until June of this year the Tri-Metric readings during equalizing
>> indicated
>> holding voltage at 31.1, with maximum amps gain of around 52.   Three
>> weeks
>> ago, when set on equalize, the maximum voltage reading was 30.7, with
>> maximum amps of 46; this was reached around noon, and by around 1:30 pm
>> voltage/amps began its typical afternoon drop-off.  I attempted equalizing
>> on two other occasions since then--the last time this past Saturday, with
>> clear skies up until mid-afternoon--but having the same results.  So, the
>> question is: are my batteries beginning their decline? We've had this set
>> for 4 1/2 years, so it would seem a bit too early for this, given that
>> these
>> batteries are expected to last 7-10 years.
>>
>>
>>
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