Question for all you solar experts

You are ordering a 24V panel? OK just exactly how are you going to connect that to your 12volt battery?

Try reading some of the stuff on the following site.

http://handybobsolar.wordpress.com/

69 Avion wrote:
I have ordered a 250 watt Sharp 24 volt Solar panel. Now for my question. I would like to use a Morningstar Sun Saver 15 MPPT controller. The problem is that the sales person said that the 15 amp MPPT Sun Saver controller isn't large enough for my panel. Does anyone have experience with this? I don't want to have to go to a 45 amp controller unless I absolutely have to.

The reason is that you will be operating at the maximum rated amps for that controller, with no safety margin. I have seen 15 amp panels produce as much as 22 amps under the right conditions, which could possibly destroy the controller.

donn0128 wrote:
You are ordering a 24V panel? OK just exactly how are you going to connect that to your 12volt battery?

The simple answer is.
They are connected to an MTTP controller, not directly to the batteries.

69 Avion wrote:
24 volt Solar panel... .. person said that the 15 amp MPPT Sun Saver controller isn't large enough for my panel.

I hope I'm expert enough to qualify! I'm not.. forget this.

250/14.4 = 17A, so you are over the limit. You won't often get 250W out of the panel. Call MS and ask if the controller will derate to protect itself and get their input on using a 250W panel.

MS MPPT 15 has a panel rating of 200w max.... plenty of posts say it works fine with 230w panels and will just clamp output at 15 amps. You may not get every watt out of the panel in ideal conditions tilted direct at the sun. However mounted flat on the roof you will be lucky to get the full 200w rating anyway.

2oldman wrote:

69 Avion wrote:
24 volt Solar panel... .. person said that the 15 amp MPPT Sun Saver controller isn't large enough for my panel.

I hope I'm expert enough to qualify!

Upon first glance it appears your controller will allow 24v input.

What's important now is to determine if the controller's amperage rating divides in half for 24v input. It probably does, meaning that at 24v your controller's max is 15/2 or 7a. You could see 10 on a good day.

At least that's what I'd be questioning.

MPPT controllers take the input voltage and current and convert it to the output voltage and current. He can possibly get 17A output, but not likely. But since this panel exceeds the controllers limit caution is the name of the game.

There are other controllers available other than Morningstar, so there is no requirement that one go all the way to 45amp.
Another valid argument that can be made for going to a larger controller it that if one desides to add to the array it will save from having to purchase an additional one or replace the existing one.

The MS Sunsaver MPPT automatically clams itself to 15 amps max output. You can put whatever size 24 volt panel you want to it. The technical libary on the MS website has a very good description of this capability and even provides examples of where exceeding the controllers nomimal max input solar power is a good thing.

Go For it, the controller is designed to do exactly what you are looking for