[RE-wrenches] Xantrex C-40 Drifting

[Steve Higgins]

Hey Drake,

How large is the battery bank?

I've seen this before on VRLA's with a couple of companies controllers. Usually this will happen with small battery banks.

Best way to explain it is when the battery bank is charging and you remove the charge, the battery is a chemical reaction... it's still charging for a short period of time even though you have removed the source.




Steve Higgins
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From: RE-wrenches [mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Drake
Sent: Friday, May 15, 2015 7:10 AM
To: RE-wrenches
Subject: Re: [RE-wrenches] Xantrex C-40 Drifting

I was thinking of a Blue Sky or a Morning Star replacement.

The Full River AGM L-16 batteries recommend a 29.4 absorption, very high for a maintenance free battery. I've triple checked this one.

At 09:30 AM 5/15/2015, you wrote:

HI Drake,

Iv'e never seen this happen. Â
But have you considered a small morningstar or similar?

A question, you list 29.4v, that seems high?

jay



On Thu, May 14, 2015 at 5:12 PM, Drake < drake.chamberlin at redwoodalliance.org<mailto:drake.chamberlin at redwoodalliance.org>> wrote:
I have a Xantrex C-40 that won't keep its settings. It is important that it does because it is for a maintainer array (80 W) on an AGM battery bank, on an AC coupled backup system. Not only could high voltage damage the batteries, but when the voltage goes over 30 Volts, the AUX relay opens and the grid tie inverter is isolated from the grid.
After numerous sessions of reprogramming, Xantrex tech support sent me a new unit. The problem persisted as before. A new temperature sensor helped, but the settings still drift. It seems that rebooting the charge controller helps for a day or so, but then it drifts again.
The potentiometer settings are way below the calculated setting for 29.4 V, but it still peaks in the high 30s. I check the temperature compensated voltages on the Outback Mate, and the temp compensated voltage runs high.
In a related side issue, the AUX relay of the FX inverters is not based on temperature compensated voltage, which makes setting AC coupling charge set points more problematic.
Has anyone experienced a C-40 CC that drifts in its settings. What would be a good (inexpensive) charge controller to accurately control 80 W of PV?
Thanks,
Drake



--
Jay Peltz
Peltz Power
jay.peltz at gmail.com<mailto:jay.peltz at gmail.com>
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