[RE-wrenches] weak voltage

Chris Anderson canderson at borregosolar.com
Sun Oct 14 21:56:13 PDT 2012


Call Dane Forsberg at SMA. Very knowledgeable. He helped me recently go
through all the settings on my 8kw SI system.

Sent from my iPhone

On Oct 14, 2012, at 9:41 PM, mac Lewis <maclewis1 at gmail.com> wrote:

Hi wrenches,

About 2 months ago, we installed an off-grid Sunny Island System.  Here are
the specs:

8.82 kW PV
SunnyBoy 8000
2 x Sunny Island 5048 Inverters
2490 Ahr SolarOne HUP batteries at 48V
30 kW Cummins Propane Generator

We are having an issue that I am having a hard time figuring out.  We are
getting sagging battery voltage, and can't seem to keep the battery voltage
and specific gravity where we want it.  In addition, I have equalized these
batteries 4 times this past month, and the specific gravity gets to about
1.25-1.26 maximum.  I have slowly eased up the boost, absorb and equalize
voltage setpoints, to try to get the battery a better charge, but it
doesn't seem to help.  The Sunny Islands don't seem to have any issue
getting these batteries up to the equalization voltage, or any of the other
voltage set points.  I have checked for loose connections, all look good
here.

The SOC monitor on the Sunny Island master, calculates that we are staying
between 70-95% SOC on a daily basis, and yet the battery voltage has
dropped below readable level a few times(I believe this is below 41V).  I
equalized at 62 V for 4 hours and had the same result of nonimpressive
sepecific gravity and saggy voltage under small load.  After we leave from
equalizing the batteries, things seem to be OK for a while and then we
start having issues again.  We are tripping a 250A battery breaker, and
getting low voltage errors on the SI, yet SOC looks good.

Right now I have the set points programmed per SolarOnes advice as:

Boost Voltage= 2.46 V/cell
Full Charge Voltage = 2.46V/cell
Equalize Voltage = 2.54V/cell

Thanks in advance for any ideas that you may have.



-- 



Mac Lewis

*

"Yo solo sé que no sé nada." -Sócrates
*

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