[RE-wrenches] Out Back FM-80 Problem

[David Palumbo]

We have an off grid system experiencing charge controller issues. 3.24kW PV
array (18) Evergreen ES-180's in (6) strings of (3) modules in series.
Approximately 77 VDC Vmp, 60 Amps typically highest charging amps into a
33.6kWh (rated storage) 48 volt battery bank. Charge controller originally
was an Apollo T-80 that never worked correctly (lots of various issues, we
ended up trying three different Apollo's before the homeowner wanted us to
try another controller). We went with a tried and true Out Back MX60 as the
80 Amp Flex was not available yet. We knew the MX 60  was outside it's
recommended PV array capabilities but we needed to get the client's PV
system charging the battery bank ASAP. We planned on upgrading to the FM-80
when available. 

 

The MX-60 worked flawlessly for several months until it failed to control
absorption charging. It would allow the batteries to charge at bulk voltage
(58.8) for hours with out switching to float (54). Absorption time was set
to two hours. Resetting and reprogramming did not resolve this situation and
the batteries were being overcharged when a couple of sunny days  were
strung together.

 

We swapped in a new FM-80 controller on April 2nd and it worked perfectly
until today. It was a sunny day and the FM-80 was in absorption mode by noon
time. The homeowner noticed at 2:30pm that the FM was not in float as it
should have been. It was a typical sunny day with no big loads on. The
homeowner reported that the FM-80 was repeatedly going through a 6 minute
cycle. Snooze for 5 minutes, wakeup 5 seconds, tracking 10 sec, bulk 30 sec,
absorb charge 20 sec, and back to snooze where it began another identical
cycle. The batteries were 100% charged by 2:000pm, the battery voltage was
at 53.5VDC (two OB VFX3648's ON powering lights and drawing 5 amps DC) when
the FM-80 was not in bulk, or absorb charge. When in bulk charge the PV amps
(35A mid afternoon, warm day) were connected to the battery bank the battery
voltage climbed back up to 58 volts quickly. The "tech" we called at Out
Back was not very helpful, "never heard of this situation" and tried to
blame it on poor battery connections,  he could not understand why the
battery voltage would be 53.5V with a 5 Amp load and then 58 volts 30
seconds later when 35 amps were charging into the batteries on a 100%
charged battery bank. 

 

Anyone else had an issue like this? Any advice?

 

Thanks,

Dave

 

David Palumbo, President

Independent Power LLC

462 Solar Way Drive

Hyde Park, VT 05655

NABCEP Certified

www.independentpowerllc.com 

 

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org/attachments/20090427/6ecfce88/attachment-0002.html>