[RE-wrenches] Corrective EQ question

Sat Jun 2 10:47:03 PDT 2012

It might matter if they are high capacity batteries, some run a stronger
electrolyte to get more out of the batteries, this results in a lower cycle
life. Ie: 350 cycle life v/s 400 cycles.  I have seen factory cells that are
fully charged at 1.315 - 1.325

To give them an EQ charge they have to finish the bulk and absorb before
they will go into an eq charge normally the control box may say eq but until
the conditions are met it will not actually happen. Then it can easily take
8 to 10 hours or longer to give them a full eq charge.

Typically they have to drive the voltage to the top of the eq range then
hold it there till the sg in the cells stop increasing.

You usually can't give it 3 hours charge 1 day then 3 the next day. I am
betting the voltage is not getting to the top of the eq range with such a
short charge time. 

I doubt that 3 hours a day will not even get the battery to a full charge,
much less start an equalize charge with them that low to start with,
especially with loads on the battery at the same time.    

Just my usual .02 worth,

Bob 

From: re-wrenches-bounces at lists.re-wrenches.org
[mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Kent
Osterberg
Sent: Friday, June 01, 2012 11:36 PM
To: Allan at positiveenergysolar.com; RE-wrenches
Subject: Re: [RE-wrenches] Corrective EQ question

Allan,

My first thought about the high s.g. measurements is that the electrolyte
level may have been low when the measurements were made. When full, there is
about a liter of electrolyte above the plates in a L16. The s.g. will rise
by 0.03 if the electrolyte level is at the top of the plates.

Kent Osterberg
Blue Mountain Solar, Inc.
www.bluemountainsolar.com
t: 541-568-4882

On 6/1/2012 1:28 PM, Allan Sindelar wrote: 

Wrenches,
A long-time off grid client has a 48V Outback VFX system, with 1,680 watts
of PV and two strings (16 batteries total) of Deka L16s, installed last
October. The array is undersized, as the system is running three households;
one efficient home and two single-person tiny homes, but still too much for
the system. We learned a few weeks ago that the system had apparently stayed
at 30-50% SOC for the entire winter (this is approximate, as her TriMetric
monitors would eventually drift away from % accuracy if never allowed to get
full and reset). Eventually the batteries became sufficiently sulfated that
the system began shutting down.

As the batteries were nearly new, we figured that the sulfation had not yet
become permanently crystallized, and they could recover. We initiated a long
"corrective equalization" from her combined generator (45A DC from the
single inverter) and MX60 controller, for a maximum C/12.5 charge rate; less
in proportion to any loads that were on while charging. She ran this
procedure for three hours/day for five days, and when that offered only
partial recovery (as measured by specific gravity measured with a
refractometer), ran for six hours/day for five days. During this time the
MX60 was also manually set to EQ each morning, with a 62V EQ voltage and 3
hour EQ time, so that the array would add its amperage to the gennie until
the batteries had been above this setting for three hours.

We went out there yesterday, arriving while the EQ was in process. All of
the cells had recovered, as measured by SG. SG readings were all in the
1.280 - 1.300 range, with most above 1.290. We had never seen SG readings
this high before. Given the situation and the back story, should we have any
concern about the high SG readings?

Thank you,
Allan

-- 
Allan Sindelar
 <mailto:Allan at positiveenergysolar.com> Allan at positiveenergysolar.com
NABCEP Certified Photovoltaic Installer
NABCEP Certified Technical Sales Professional
New Mexico EE98J Journeyman Electrician
Founder and Chief Technology Officer
Positive Energy, Inc.
3209 Richards Lane (note new address)
Santa Fe, New Mexico 87507
505 424-1112
www.positiveenergysolar.com <http://www.positiveenergysolar.com/>  

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