I've not had good luck on Surrette 5000s actually. We had a set that
was really problematic early on with battery voltage temporarily
dropping below the inverter lo volt shut off, when a well pump was
started. They have amp hours rated at the 100 hr rate, and they seem to
behave as expected when the discharge rates are kept to the hundred hour
rate. (19 amps from a 1900ah @ 100 hr rate)
For the problem set, I added another 6 v, and actually created a 54 v
nominal battery bank. That solved the problem for about 5 years, but
then the lo volt problem crept back up, and they replaced the whole set
at about 6 years as I recall. This was seriously embarrassing for us,
as it was an expensive battery bank that I had touted as being able to
go 15 years under normal conditions.
They're rated to 1500 cycles at 80% DOD, but again, I only think that's
true at lower discharge rates. I just never could figure out the
Surrette 5000s, and heard enough other folks having trouble, that we
moved away from them. At 10 years, I'd say all bets are off that it's a
good bank. I just had an aging set of L16s with remarkably even cell
voltages, that seemed to perform well under load testing, totally crash,
less than 6 months later.
R.Ray Walters
CTO, Solarray, Inc
Nabcep Certified PV Installer,
Licensed Master Electrician
Solar Design Engineer
303 505-8760
On 11/18/2013 6:31 PM, Allan Sindelar wrote:
Ray,
Yes, I know...
Doesn't ten years seem a bit weak on a set of Surrette's best? And the
other ten cells are remarkably even. If replacement (which is already
being arranged by Surrette in a good way) gives 3-5 more years, even
with keeping a close eye on cell variations, we have accomplished a
reasonable objective.
Re a loose connection: this is why I posted the questions: to look for
other possible explanations. Did you see Nick's response: "I used to
see that arc flash all the time from the SW series relays, even on new
SW Series inverters. That always happened when the contact switched
under load." I'd consider this before pulling the cover off to look
for the source of the flash.
Re the single-string issue, Steve Higgins replied very promptly (as
did James Surrette, to whom I had written before posting here), saying "
What you can do to save some fuel is pull the two cells out and reduce
charge voltage per cell... this means if your absorbing at 28.8, then
you adjust the voltage down 2.4vpc to 24vdc...
If you do this you may also want to adjust the LBCO as low as
possible. If you leave the dead cells in it's just going to consume
more fuel to keep charged."
But we agreed that the new cells would be in place soon enough to not
justify this course of action. I have done the one-string-from-two
temporary solution many times over the years.
Thank you,
Allan
*Allan Sindelar*
_Allan@positiveenergysolar.com_ <mailto:al...@positiveenergysolar.com>
NABCEP Certified PV Installation Professional
NABCEP Certified Technical Sales Professional
New Mexico EE98J Journeyman Electrician
Founder, *Positive Energy, Inc.*
A Certified B Corporation^TM
3209 Richards Lane
Santa Fe, New Mexico 87507
*505 424-1112 office 780-2738 cell*
_www.positiveenergysolar.com_ <http://www.positiveenergysolar.com/>
On 11/18/2013 6:13 PM, Ray Walters wrote:
I thought the relays on the SWs were sealed, so visible arcing sounds
bad. Are you sure its not a loose connection?
Also on the batteries, anytime I've ever seen someone replace just a
couple of cells in a bank that old, it never ended well. It was like
that gopher stomping game, and you hit one problem, and then another
pops up right after.....
We need some kind of financing program for battery replacements, so
that people can get what they really need: a whole new set.
That very situation, is why I quit doing as many single series
strings: one or two cells fail, and the whole system goes.
In this same situation with 2 strings, you create a single string of
your strongest cells to limp the customer along, until they can
afford to replace the set. As cells go down, you keep pulling in
replacements from the retired string. This would be a great time to
take a few of the best used cells from another aging set on another
system that is getting replaced.
R.Ray Walters
CTO, Solarray, Inc
Nabcep Certified PV Installer,
Licensed Master Electrician
Solar Design Engineer
303 505-8760
On 11/18/2013 5:01 PM, Allan Sindelar wrote:
Wrenches,
A longtime off grid customer with a 1997-era Trace SW4024 and a
Kohler 8.5RMY backup generator (with 1,800 hours over 16 years) has
never had an inverter failure, but requested my assistance with a
recent development. His generator has been set up on automatic
operation using standard Trace voltage, quiet time and load-start
program parameters. When it was called to run, it would charge to
29.6 V with a one-hour absorption, then shut off. This has worked
well until recently. The automatic operation includes a cool-down
and the modest absorption means that the AC input current at
shutdown is going to be pretty low.
Recently he called me because his generator was starting more
frequently and running for longer duration. Of course, I immediately
suspected the batteries, which are ten-year old 5000 series Surrette
4KS-25PS cells. Upon checking I found two weak cells, which would
explain the inability of the batteries to reach full voltage and
shut off after absorption. I will be replacing these two cells,
which fortunately are both within the same red polypropylene case,
as our only option, as the homeowner's budget won't allow
replacement of the whole set. As a single string, the two new cells
should play reasonably well with the old cells for a few more years.
Because of this, the homeowner had recently shut off the generator
at night using the buttons on the inverter, and when he did this he
saw a spark flash from inside the inverter on the AC end. I was able
to duplicate the flash, which I assume to be the AC2 input relay.
The AC2 In setpoint is set to maximum 35A AC. Until the failed cells
are replaced, I have advised the homeowner to manually control the
generator at the generator, using its AC output breaker to
disconnect the current to the inverter before the 108V AC default
input voltage threshold causes the inverter AC input relay to
unlatch under load. While the SW latches while unloaded and then
ramps up input current, I don't believe that it can reduce input
current to zero before unlatching when shutting down.
My guess is that after 15 years of flawless performance, the relay
contacts have pitted enough to cause arcing at disconnect, and if
not addressed, the relay on the AC board will eventually fail. As AC
relay boards these days are likely made out of unobtanium, I'd
rather avoid this failure.
So my questions, please:
1. Have I likely correctly identified the AC input relay as the most
likely cause of the visible arcing when the generator is turned off
at the inverter?
2. Should manual control be a permanent solution?
3. Any other suggestions for this customer?
Thank you,
Allan
--
*Allan Sindelar*
_Allan@positiveenergysolar.com_ <mailto:al...@positiveenergysolar.com>
NABCEP Certified PV Installation Professional
NABCEP Certified Technical Sales Professional
New Mexico EE98J Journeyman Electrician
Founder, *Positive Energy, Inc.*
A Certified B Corporation^TM
3209 Richards Lane
Santa Fe, New Mexico 87507
*505 424-1112 office 780-2738 cell*
_www.positiveenergysolar.com_ <http://www.positiveenergysolar.com/>
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