[RE-wrenches] weak voltage

[William Miller]

Mac:

We had a similar problem with a large bank of IBE 2 volt cells.  The 
batteries had to be removed the same day they were installed and then 
reinstalled the next day.  They sat outside for one night.  The flags 
acquired an invisible but insidious corrosion that caused problems getting 
and keeping a charge.  Now we insist on cleaning each flag and eyelet no 
more than 10 minutes prior to contact.

William Miller


At 09:41 PM 10/14/2012, you 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.
>
>
>
>--