Thanks a lot Bob for this . I was going by recommendations for charging=20 Powersonic AGM cells which calls for a charging voltage of 2.4 to 2.5=20 volts per cell so for a 12 volt battery 14.6 volts to 15 volts. They=20 call for a float charge voltage of 2.275 volts per cell or 13.7 volts .=20 Maybe different AGM batteries call for different curves. Since this is=20 not a serious solar installation only being used on occasional camping=20 trips maybe I am getting worked up for nothing. It sounds like your=20 experience of using 14.2 volts has been satisfactory. Thanks again for=20 the advice. Cheers, Jim > Hi Jim, > > The correct voltage depends on what you want to do. Choose a higher volta= ge if you want fastest charging and the highest amount of energy storage. C= hoose a lower voltage if you want long life for your battery. > > Personally I would not go higher than 14.2 for an AGM battery. I think my= Miata cuts off at 14.0 to 14.2(it is factory equipped with AGM battery). A= nd in a car it is only charged for short periods. > > If you hold an AGM battery at more than 13.8 volts after it has fully cha= rged, you will steal away some useful life. Or so I am told. > > Best regards, > Bob > > ________________________________________ > From: piclist-bounces@mit.edu on behalf of Jim = Ruxton > Sent: Tuesday, August 15, 2017 9:51 AM > To: Microcontroller discussion list - Public. > Subject: [OT] Charge Controller for AGM batteries > > I have seen some folks on here who are pretty savy about solar > applications so I thought I would pose this question here. I just bought > a 40 watt panel that came with this charge controller . > https://www.walmart.ca/en/ip/7-amp-solar-charge-controller/6000086038819 > . I want to use it with a smallish ie. 18 AH battery . I wanted the > battery to be fairly portable and low maintenance so have been looking > at SLA AGM batteries . Unfortunately this charge controllers cut out > voltage is 14.2 volts and from what I have read this is too low for AGM > batteries. I was thinking about hacking into the charge controller and > trying to change the cutoff voltage. Maybe not the quickest option. I > was also thinking of getting a charge controller with a higher cut off > voltage. My other option is to use a different battery. Just wondering > if others have thoughts on the direction they would go in this > situation. I didn't want to spend a lot for a new charge controller. I > was looking at this one. > https://www.amazon.ca/Samlex-SCC-1208L-Amp-Charge-Controller/dp/B00B2AT6E= S > And of course there is the option of a PIC based home brew controller > ... Any thoughts? > > Thanks, > > Jim --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .