Array Sizing

[Beek's Bluffs]

I already have a 12V system set up at my off grid cabin. I want to change my solar array. I have a aims ssc-60a mppt charge controller and want to put 6 panels up. All 400 watt. 3 in a series then the 2 series paralleled together.
Each panel has a VOC 37.07V and ISC of 13.79 amps.
I rounded up to come up with 2 strings 120V and 14Amps parelelled together giving me 120v at 28amps. The operating volts on charge controller are 5-150V and amps is 60 amps.
To me this makes sense but the tech at AIMS is saying that 800 watt array is as big as I can use. Seems like it would be very difficult to hit 60 amps with a 800 watt array.
Any help would be appreciated.

The new array is in prep for new 48V system coming in a year or two.

 

[seneysolar]

When hooked to a 12V system, figure 2400W / 12V = 200A output from Charge controller. Now, obviously the controller won't do that and a lot of people on here "over-panel", but I wouldn't over-panel by that much. I think 800-1000w would be ok. Over paneling works good on cloudy days but I have found it really raises the temps on the charge controller on a sunny day. Maybe you can get your array up and use a combiner box. Run 3 strings of 2, and just leave 2 of the breakers turned off while you are still 12V.

When you migrate to the 48V system, you'll be fine. 2400W / 48 = 50A

This is why its costly to expand 12V systems, you end up with high currents because of the low voltage. Large charge controllers get expensive.

 

[Beek's Bluffs]

Thanks, yes I have done a lot more research and figured this out.

 

[DIYrich]

The operating volts on charge controller are 5-150V and amps is 60 amps.

I looked at the manual for Aims, but don't know if it is your specific model. It does have a Max PV Input of 800W at 12v.
The max charge current of 60a is still subject to the max PV input of 800w. The lower the voltage, the higher your amps can be.

At 120v, the max current would be 6.7a to max out the 800w. At that point, you are at the 14v 60amp limit to the Battery.

 

[dopeassjackson]

One thing you may have a big issue with is the 120v pannel output and 150v max input on the CC. If your in a cold climate it may be close on hitting the 150v max, but I havent run the numbers.

If the area you want to fit the pannels will take 6 pannels than put 6 pannels up. You dont need to use all of them. You will also be luckey to see 90% of the pannel output.

You could always add another CC later and hook it up to the pannels you didnt use with the first one.

 

[Beek's Bluffs]

From what I have looked into, I think I am interpreting this correctly. As long as the max input is below 800 watts I should be okay with a bigger array. Obviously not with the full array, but I am in extreme northern Michigan where we get less the 4 hours of premium sun per day. I will test some panels and see where I am at. I have a second setup I can test 1 panel at a time.

 

[DIYrich]

From what I have looked into, I think I am interpreting this correctly. As long as the max input is below 800 watts I should be okay with a bigger array. Obviously not with the full array, but I am in extreme northern Michigan where we get less the 4 hours of premium sun per day. I will test some panels and see where I am at. I have a second setup I can test 1 panel at a time.

It will work. Instead of 6 panels (2400 watts) on one 800w controller, you would be better off with 4 panels on two 800w controllers. That assumes your batteries can be charged that fast.