C35 charge controller issue

[Lifetide]

What a great resource this site is. Anyway, I wonder if anyone can shed some light on my Xantrex C35 charge controller. I actually have three of them on three different systems on my off grid property, so I'm no stranger to them (though I'm certainly no expert). Without going into the specifics of the small system, it's been operating perfectly for years until recently--even outlasted several banks of golf cart batteries. As of several weeks, it doesn't seem to be accurately monitoring the charge nor cutting down the 12 volt input. The green light still blinks, but only one blink as if the system is not near a full charge. However the batteries are obviously being over charged--according to the ambient charge at night showing on my voltmeter and the electrolyte boiling away. The ampmeter shows the charge to be coming in even when I know they're fully charged. I've tried manually cutting off the panels and running down the batteries somewhat to no effect; when I open up the circuit again they just come back up and overcharge again. I can trigger the equalization and it blinks green/red as usual. I wonder if there's a way to reset the controller or if it's just lived out it's useful life.

[vtmaps]

Is it possible that your battery has a shorted cell? Since you have three systems you can do some diagnostic tests: swap batteries or controllers between two of your systems. --vtMaps

[BB.]

There have also been posts here about C series chargers that simply stop working correctly with no obvious signs other than the batteries not being properly maintained. Perhaps it is time to replace it.

-Bill

[niel]

you stated that you have 3 separate systems with c35 controllers, now are all of them acting badly or just one? is it just 3 separate pv systems going into their own c35 and on to a common battery bank or are the batteries separate banks and dedicated to only one pv/c35 system?

[Lifetide]

In answer to niel...The three systems are completely independent, including the batteries.

[Lifetide]

In reply to vtmaps...I use golf cart batteries, and my voltmeter shows their ambient charges ranging from 6.35 to 6.40. I thought that indicated good batteries, especially since they're holding the charge. Anyway, I'll check the cells with my hydrometer and see if any of them are bad. As far as swapping things around, the systems are spread around 7.5 acres, so I was trying to avoid lugging batteries around to systems that have batteries of different ages or disconnecting and reconnecting charge controllers. I guess swapping charge controllers might be the way to go. I appreciate your response.

[niel]

In answer to niel...The three systems are completely independent, including the batteries.

that half answered my question for you did not say if all c35 controllers are acting bad, 2 of them or just one.

[Lifetide]

Thanks to those who replied to my question about the C-35 charge controller. I did test the cells with a hydrometer and they were all okay. Strangely, after shutting off the power coming in from the panels for a couple of days, the charge controller started working again. I had tried shutting down the power briefly in the hopes that it might reset itself without any luck. But when I shut the system down for two days (no power coming into and no draw on the batteries), the controller popped back to life functioning normally. It came on line with just a one blip flash, and I thought that the problem was unchanged; but after about two minutes, it went to two blips and now seems to working normally again. I have no explanation for why, other then with a sufficient period of time offline, it reset itself.