[RE-wrenches] Mystery: C-40 controllers "stuck" in EQ mode

[wes kennedy]

HI Mick,

The C-40 tries to hold an equalizing voltage for 4 hours to "complete" the action. With a system such as you described:  big, old bank of questionable functionality, the c40 could live forever in equalize mode. 



-Wes Kennedy

303-653-3073
NABCEPian

--- On Fri, 5/28/10, Mick Abraham <mick at abrahamsolar.com> wrote:

From: Mick Abraham <mick at abrahamsolar.com>
Subject: [RE-wrenches] Mystery: C-40 controllers "stuck" in EQ mode
To: "RE-wrenches" <re-wrenches at lists.re-wrenches.org>
Date: Friday, May 28, 2010, 9:17 AM

Hi, Detectives~

At a client's off-grid home I observed two side-by-side Trace C-40 PV controllers, circa 1998, which were "stuck" in equalize mode. Day after day they did the red/green blink and they would not throttle back the incoming solar energy. This was with the jumper set for automatic EQ (should have been once per 30 days). I changed the jumpers to Manual EQ and normal behavior ensued: green blink with proper throttle back.



Clues: The battery is huge compared to the solar recharge current. The battery is also old and may have high self-discharge. Internal shorts in one or more battery cells are also possible. Because of these factors, the battery voltage was not reaching a high value even though the controllers were running wide open.



I thought that when the sun set, any auto EQ behavior on the C-40 would cease, but that didn't happen in this case. A product failure seems non-likely unless they both happened to break in the same way. Is there some other condition which the C-40 must see in order to be satisfied that it's OK to end the EQ?



Thanks in advance for helping me solve this mystery,

Mick Abraham, Proprietor
www.abrahamsolar.com

Voice: 970-731-4675


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