Last year I bought 4 used 6v Rolls batteries which are connected to a mppt controller (tracer). I noticed the batteries (according to the monitor attached to the mppt) seemed to be draining far too fast so I came to the conclusion I'd bought duff batteries that weren't holding charge.
This year my 2 fan vents will not run, the error message on both of them tells me it's a problem with under voltage yet my led lights work ok.
I figured my batteries are on their last legs so bought a multimeter to check them.
After disconnecting them and allowing them to rest I read 6.5v on each of them (which I understand indicates fully charged), over the last few days I've kept them disconnected and read the volatge multiple times and it's remaining constant so they aren't loosing charge rapidly.
One of the batteries terminals had begun to corrode so I cleaned them up wondering if that would cause a volatge drop. Once reconnected to the mppt I measure 6.4v on each battery. I checked the connections from the batteries to the mppt and and am getting 12.79v, I checked the leads running to the fans and get 12.79v at both the fuse box and the fan end.
I feel like I keep banging on about my batteries but I'm running out of ideas. Why would the mppt show them as depleted if a multimeter reads them as full? Why would the fans indicate low voltage and fail to start if full voltage is reaching them?
I was prepared to buy new batteries but it seems like the batteries might be ok. Can anyone help? Any advise would be sorely appreciated. Is anyone fairly local and good with batteries who could possibly take a look for me?
Thanks in advance