I have a question. The specific gravity is an indicator of the
concentration of the sulphuric acid in the cell as I understand it.
If the SG is very high (as reported) then the sulphate ions must be
mostly in the electrolyte and not on the plates. This makes me ask,
how can it be that the plates are sulphated with high SG? (sorry for
my quaint olde worlde spelling)
Another thing I would ask is why not give the customer a $10
multimeter and instructions how to check each battery ("press hard
with the tip of the probe" etc). Then when the voltage plunges down,
and before recharging, ask them to check each battery with this
meter? That would identify or rule out the intermittent internal
resistance theory. If it exists, it's just in one battery.
Presumably.
Hugh
Larry, the customer has been fully charging and equalizing every
week to two weeks for several years. They also are diligent about
checking the batteries with a hydrometer. It turns out then that I,
and the customer, have put too much faith in hydrometer readings to
give an accurate picture of battery health? Yes I agree (long time
ago) the battery monitor would have been helpful in catching the
problem - if this is the problem. A couple of other posters have
suggested another possibility: a fractured bus bar inside the
battery or a dead cell. Both of these suggestions came from people
who experienced almost identical problems that were extremely
difficult to detect. I have recovered several sets of sulphated
batteries, Surrettes, Trojans, Yuasa, so I know what they are like
and what they smell like when subjected to a high amp charge.
I have several sets of these KS25's & 21's in the field and for the
most part they have worked very well but I've seen customers
sulphate L-16's in a few weeks of deficit charging, it just takes
longer with a big battery especially when they aren't really being
abused.
I'm sure hoping the horse hasn't left the barn on this one.
Ron Young
On 2011-11-17, at 12:32 PM, Larry Crutcher, Starlight Solar Power
Systems wrote:
Ron,
From what Daryl said below and the fact that your customer has
about 15 amps of PV charge, you should deduct that the batteries
have MOSTLY been deficit charged their entire life. Here's what I
told you on Oct 22 in my lengthy explanation about what the problem
is and why it happened: "Undersized RE charging systems, or perhaps
oversized batteries, is the culprit that contributes to this all
too frequent phenomenon of chronic undercharging."
You said that the customer has been compensating for an undersized
system by running a generator. They can not know this because there
is no monitor. The batteries now have a sulfation problem, perhaps
unrecoverable, that could have been prevented if the owner had a
battery capacity monitor. This is not pleasant news, I know. I have
to explain this bad news to people MANY times each week. This is a
huge issue globally. And such waste of money, time and resources
just bugs me!
Larry Crutcher
Barer of Bad News
Starlight Solar Power Systems
On Nov 17, 2011, at 5:17 AM, penobscotso...@midmaine.com wrote:
Ron,
I'm going to reiterate what Jeff says here. It is similar to what I had
said in my email. The charge rate must REGULARLY be C10 on the KS
(5000 series) batteries. This means, on KS 25's, a routine bulk
charging rate of 135 amps. I find that on these types of hybrid
systems, while the batteries might occasionally (sunny day, generator
running, etc.) that kind of charging, they do not regularly see C10. I
think if you gave Jamie Surrette a call he would give you the same
possible assessment.
I do think the problem is oversulfation, but none of this solves your
problem, I know. We have been installing KS series batteries since they
came out and this necessity of regular C10 charging has been an
integral part of design for me for many years.
>>
Best,
Daryl
Ron,
This reply a little late since I have been off line a few days. I
mentioned
in a similar thread last year that I had an off grid home client I
designed
and installed in Idaho back in 1998 that had a Kohler 8.5 kw generator, a
Trace 4024 inverter, two separate solar arrays and Outback charge
controllers, and 16 Trojan "L-16" batteries. This system worked
flawlessly
for 7 years and only required the generator a few hours per month, then it
was time to change the batteries. I replaced the Trojans with the same
size
battery made by Surrette and everything went to crap. They had to run the
generator hours and hours to get them past an 80% charge and we had lots
of
problems with overloading the generator even though we did not make any
program changes and used the same generator. The generator was replaced 2
years later but this system never worked like it did before the battery
replacement.
When researching all this at that time I had talked with Surrette, Trojan,
and anyone else that might help and this is what I found out. Of course
there are just my opinions based on these conversations, but it is my
understanding that Surrette is a much longer life battery with much less
water loss when comparing apples and apples, and I was told this was due
to
a different lead composition that Surrette uses than any other battery
manufacturer. However, this difference requires a much longer
absorption/taper off charge process or you will never get it past 80%
charged. This of course is almost impossible to achieve with a generator
or
undersized solar array, and you really need a grid connection to fully
charge these things. No doubt these would be great in some standby grid
connected system but I no longer use them in off grid. This was also at a
time when battery manufacturers were just discovering solar so maybe
battery
designs have changed. Again, I think Surrette is a good company and makes
a
great battery, but just not sure you can fully recharge them with a
mid-sized generator.
I also do not like using parallel battery layouts as its hard to keep one
string from pulling down the other strings when there is a low performance
cell so you might do a cell by cell check.
Good Luck,
Jeff Yago
DTI Solar Inc.
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