We have lots of C40's out there, though not generally with such small PV input, don't recall any issues with drifting. I just installed one and verifying the potentiometer settings with DVM was bang on. For a recommended substitute, consider the Blue Sky units such as: http://www.blueskyenergyinc.com/products/details/solar_boost_1524ix We use in lots of industrial telemetry sites with similar configs - small PV with AGM batts. Solid performing controller with a bonus of some datalogging. Kevin
-----Original Message----- From: RE-wrenches [mailto:[email protected]]On Behalf Of Drake Sent: May 14, 2015 4:12 PM To: [email protected] Subject: [RE-wrenches] Xantrex C-40 Drifting 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 Drake Chamberlin Athens Electric LLC OH License 44810 CO License 3773 NABCEP Certified Solar PV 740-448-7328 http://athens-electric.com/
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