48V solar array for 12V battery bank?

[austintysver]

Is it possible to use an MPPT charge controller, capable of 48v, with a solar array of 48v to charge a 12v battery bank? I currently have 4 group 24 lead acid deep cycle batteries hooked in parallel that I would like to keep maintained while boondocking. I have been looking all over the internet for the answer to this question but I have been unsuccessful at getting a clear yes or no answer.

 

[upnorthandpersonal]

Yes. Solar can be (much) higher voltage than the battery - it depends on the MPPT. Just make sure you're using the Voc (open circuit) voltage of the panels and not their nominal voltage to decide whether your MPPT can handle it (you want to stay below the max it can handle at all times).

 

[JoeHam]

YES.

I’ve used a panel with over 50v to charge my 12v nominal LiFePO4 batteries via a PCM60X SCC.

 

[tictag]

The best way of thinking about this is that a SCC, any SCC, has two independent 'faces', one side faces the PV array, the other faces the battery - and they can be totally different in terms of voltages and currents. You can have a 2,000W PV array at 250V on one side, with a tiny 20AH 12V golf battery on the other (bit extreme, but do you understand what I mean?). It's the SCC's job to buck the PV voltage down and control the charging current to whatever the battery needs.

Solar panels are (unfortunately) marketed at 12V/24V etc This is just marketing, designed to group together compatible products. In reality, all PV panels are different ... for example, a panel designed for a 12V system will most likely have a 21.6Voc output (36 cells x 0.6v per cell = 21.6V).

You just need to make sure that the panel/array Voc is higher than the battery system. Most SCCs demand at least 5V higher to begin charging then at least 1V higher to continue charging. For example, a 48V (nominal) battery needs a 57.6V charging voltage, your array must provide at least 62.6V to start charging and must maintain at least 58.6V to continue charging. If your array is producing near 150V (the maximum PV voltage limit for most consumer-level SCCs), the SCC will very likely turn on very early morning (i.e. array output goes above 62.6V) and stay on well into the evening (i.e. array dips below 58.6V).

So to answer your question directly, YES, a 12V (nominal) battery needs at least 19.4V (14.4V charge voltage + 5V for the SCC) on the PV side to start then at least 15.4V to continue. It'll sit pretty with 48V

Edit: Corrected typo.