Which MPPT Charge Controller can handle my solar?

[dr_nelson]

Hey y'all,

As you may know, I know nothing about electrical stuff.
So, I have two solar panels arriving soon. The specs per panel say:

• Max System Voltage (IEC/UL) 600V
• Maximum Power Pmax 180 W (0%, +3%) 
• CEC Listed PTC Power 158.3 W
• Voltage at Maximum Power Point Vmpp 19.67 V 
• Current at Maximum Power Point Impp 9.15 A
• Open Circuit Voltage Voc 24.06 V
• Short Circuit Current Isc 9.77 A 
• Module Efficiency (%) 18.0% 

Since I will have two of them, I will have 360 Watts of solar panels to start with. I will probably add another 100 W solar panel down the road, which will make a 460 W set on my roof. I will start with 235 AH house battery (two 6 V golf cart batteries). I am thinking 360 W should be able to fully charge 235 AH battery, even in winter in SC. I plan to "install" a 12 V system in the van. Almost everything I will try to keep 12 V, and maybe only need a small inverter to run a Playstation.

Now, I need a solar charge controller. I have decided to go with an MPPT charge controller (so, this thread is not really about PMW or MPPT, or do I have enough solar for my needs, etc.). I tried looking and reading but it's like a foreign language to me and I think I had enough of the "analysis paralysis". What I cannot figure out is, what do I have to look for in an MPPT charge controller to make sure it can handle my up-to 460 W of solar?

I am looking at two charge controllers right now:

1.  "12V/30A 400W MPPT Solar Boost 3000i Solar Charge Controller SB3000i"
2. "Morningstar TS-MPPT-30 TriStar 30 amp MPPT Solar Charge Controller"

Something tells me that these charge controllers might be not good enough to handle my solar. But I don't know what I have to look for to make sure a MPPT charge controller can handle my "up to" 460 W panels.

Any help greatly appreciated! Please keep in mind you are dealing with a Super-Noob here...
Thank you,
dr_nelson

 

[jimindenver]

Both are quality controllers. 30 amp is enough to handle the two larger panels and you will never be able to add a 100w to them as the voltages are vastly different.

 

[galladanb]

Hey Doc!

I kinda asked a similar question in another thread in here.
I wanted to plan ahead and add a suitcase later, 200w now.

The answer I got was proceed with the 200w kit and add the suitcase later using a second controller, one that was suitable for the suitcase system.

It was suggested that I simply add the suitcase when needed, by using squeeze clamps, direct to the batteries.
Along with the rooftop installed system and at the same time. The suggestion implied that both could run at the same time, and both charge the batteries together.

Maybe this idea could work for you as well. I know you want to add the third panel later, but that might not work like you want? Everything I've read and understand from this forum and others is do it all at the same time, mix and match doesn't work too well...

Hope this helps?

Such Fun!!!

 

[dr_nelson]

Yeah thanks, definitely helps to know that not every panels can be mixed. Looks like I will have to go with a separate charge controller later, bummer. It also helps to know that a 30 A charge controller is more than enough.


But what I still haven't figured out, how do I know a MPPT charge controller can handle two panels that say:

• Voltage at Maximum Power Point Vmpp 19.67 V 
• Current at Maximum Power Point Impp 9.15 A
• Open Circuit Voltage Voc 24.06 V
• Short Circuit Current Isc 9.77 A 

What numbers do I have to look at to decide on a charge controller?

Is an e.g. 30 A charge controller OK because it can handle two panels of 9.15 A Impp Current at Max Power Point?
(Because 9.15 A times 2 is 18.30 A Impp, and this is still below 30 A?)

Or do I have to look at the Short Circuit Current Isc, i.e. 9.77 A times 2 which equals 19.54 A and also would be still below 30 A?


And if so, does that mean I could go with a charge controller that has less amps (and probably save some money), i.e. 20 A and not add any more panels to it? Or would that be too close to the max?

Everywhere I read or hear that one needs a charge controller that can handle the power, but nowhere can I find how to determine that (or maybe it is out there, but I simply don't understand the electrical jibberish).

 

[jimindenver]

The 30a rating is the output resulting from the panels. 400w is generally the limits listed for a 30a MPPT controller. Another limit is Voc be it with the panels in parallel or in series. In parallel the Voc would be 24.06v. In series it would be 48.12v. I believe both controllers would handle either but always check the info for the controller.

 

[dr_nelson]

Hey Doc!

I kinda asked a similar question in another thread in here.
I wanted to plan ahead and add a suitcase later, 200w now.
(...)
Such Fun!!!

I looked at this thread of yours.

"Fun" is different...  :-/  I knew that the electrical part would be the biggest challenge for me, but I know I can do it with this forum

 

[Gunny]

dr nelson, at one time I thought I was reasonably intelligent and then along came solar. I have had guidance from JiminDenver and several others on this great forum and by the time I try and research what I need without having to message or call someone, my eyes glaze over and I take a Xanax.

I bought two panels yesterday on a leap of faith that I can make both fit, if not, one will become an expensive frizbee.

If both panels will fit, I will have almost 600 watts. The salesperson told me I would be at the upper end (whatever the hell that is) of the limits of a 40amp MPPT and should consider a 60 amp. I am of the theory that it's better to have too much than not enough, as long as too much does no harm, except to your wallet.

Rob