Posts: 7Registered Users
Hello,

I am building some panels to charge my small battery bank. ( 2 or 3 deep cycle) I am building, for now, two 144 watt, 20volt 3.6 amp panels and plan on getting the morningstar 30 charge controler. Can I put those two panels in parallel to get 20 volts at 7 amps or 4 panels at 14 amps and have it be enough to charge my 3 batteries. Can I use the batteries while charging? I have a 2000/4000 watt inverter that works real well with 2 batteries right now. I take the batteries and charge them at home to bring up to my cabin. SO the bottom line, can I hook up my panels like that? Is 20 volts at 7 amps enough to charge 3 deep cycles? Also can I use them while charging?

Jeff

• Posts: 17,615Banned ✭✭

Welcome to the forum.

There's one critical piece of information missing from your question: How big (in Volts & Amp hours) are the batteries?

You will have (with luck) 288 Watts of panel. Normally that's enough to charge 150 to 300 Amp hours of 12 Volt battery.

How you hook the panels up depends on a couple of things: the actual Vmp of the panels and whether you use an MPPT or PWM controller. The Morningstar 30 Amp http://www.solar-electric.com/ps-30.html or http://www.solar-electric.com/ps-30m.html is a PWM type, and is meant to work with nominal array Voltage that is the same as the nominal battery Voltage. This would usually mean a panel Vmp of about 17.5 Volts for a "12 Volt" system.

You should be able to continue to use the system while charging. But remember the net charge value under those circumstances is the Amps out of the controller minus the Amps going in to the inverter.
• Posts: 7Registered Users

Thank you for the responce. You lost me a little on the amp minus amps from the charge controller. Is there a easier way to describe that? I believe the batteries are 125 amphour. I was looking at the morningstar ps-30m. Again, thank you.

Jeff
• Posts: 17,615Banned ✭✭

Okay, a little reading material to start off with. The Battery FAQ's: http://www.windsun.com/Batteries/Battery_FAQ.htm

Basically you want to achieve a charge current between 5% and 13% of the batteries' "20 hour" AMp hour rating. The thing is, the Amps actually going in to the batteries while the inverter is on is the Amps coming out of the charge controller less what is going to the inverter to supply loads. For example:

15 Amps from controller less 3 Amps being used by inverter & loads equals 12 Amps actually charging the batteries.

I think you could expect bout 15 Amps from 288 Watts of panel. The "basic" formula for that looks like this:

288 Watts @ typical 77% efficiency = 221 Watts / 14.2 Volts charging = 15.5 Amps

15 Amps is 5% of 300 Amp hours or 10% of 150 Amp hours or 13% of 115 Amp hours, to explain the battery range possible.
• Posts: 7Registered Users