[RE-wrenches] Troubleshooting Off-grid PV

Sun May 27 16:37:16 PDT 2012

Hi Eric,

Check the dates on the KC-120 module label. If any were manufactured between January 1999 and December 2002, they have or will fail. We have been replacing these modules for over 8 years now. There was a defective solder joint during manufacture. Kyocera will still replace them under warranty even though they have no legal requirement to do so. They will ship you remanufactured 120's and pay for return shipping. Contact Kyocera about the procedure. 

If the batteries are sulfated, they will not produce the load necessary to drive the current high. Capacity has nothing to do with it; internal resistance does. You can test the array by pulling the voltage down (turn on some big loads) at solar noon. This will force the controller into bulk and reveal the maximum current the array can produce. I think you have two problems here. With bad modules, you may not see much.

It is typical for a controller to transition to float very early in the charge cycle if the battery is sulfated. Look for a fast rise in voltage in the morning. This is an indicator of sulfated battery. A healthy battery will slowly climb in voltage.

Let me k now if you need more understanding about batteries, charging and why MOST of them never see old age. It's my speciality.

Larry Crutcher
Starlight Solar Power Systems
(928) 342-9103

On May 27, 2012, at 2:50 PM, Eric Stikes wrote:

Hi Wrenches,

I inherited an off-grid PV system that seems to be significantly under producing. I have:

12 KC120's (~17V 7A each) paired up 2 in series, for 6 strings terminated on new 15A breakers in a new Midnite combiner,
Output of combiner passes through a 60A breaker then into a SolarBoost 50 charge controller. An SW4024 ties in the CC, a Kohler 8.5 Gen set, and a Yuasa 24V battery bank.

My problem is that I never see more than about 5A (displayed at charge controller) coming off the array, even in full sun, regardless of the state of charge of the batteries. I figure I should see, at least once in a while, closer to between 20-30A. Batteries are, admittedly, passed their life expectancy as the system was installed in '02 and I am sure this is part of the problem. I'm thinking that if the batteries are at about 1/2 capacity (don't own a hydrometer...yet), the controller senses the batteries are near full SOC even at lower voltage (~24V) and is therefore attempting to trickle charge even in the bulk stage. Though this is not how the CC is supposed to function in bulk, obviously, I'm assuming the old batteries are altering the standard operating conditions of the system. I've adjusted the Bulk set point on the CC but that doesn't seem to make a difference.

I doubt this is part of the problem but the generator is problematic as well (it has it's own array of maladies).

Any insight is greatly appreciated. Thanks!

-- 
Eric Stikes
Owner
SunHarvest Solar
+1 (530) 798 - 3738
www.harvesthesun.com
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