are Mppt controllers worth it for 12 volt panels?

[landslide03]

Hi

I am looking for a charge controller for my solar setup. so far i have a 120 watt setup on 12 volt panels. I am eventually looking to expand to about 500 watts. My question is, do i really need a mppt charger for 12 volt panels or do i only need i if i have higher voltage panels. I was thinking about getting a morningstar ps-30m controller, will it be alot more efficient if i pay the extra money for the mppt controller?

Thanks

[john p]

My answer is no dont get a MPPT controller for that size Use the extra money to buy a bigger solar panel.. far better return for your dollar

[russ]

If your panel output voltage is close to the range you will use - say 17 volts for a 12 volt system - you gain little from a MPPT controller.

If the panel output is 40 volts and you are charging a 12 volt battery system at 17 volts then you lose significantly.

You need to select the correct panels for the controller or the opposite. Mismatches are where you lose out.

Russ

[landslide03]

Thanks guys for the input, this is my first setup so i am sure i will be buying a second set of things later on if i decide to really get into it. Well i decided to go with a mppt controller. it is a digital lcd one from china, I got it for about 20 bucks more than a standard one on ebay. hopefully it works for a season until i can afford a nicer name brand ne.

[russ]

I would suggest you put it in a place so that if you happen to have an incident it will not burn your house down. It may work perfectly fine for you but better safe than sorry.

Equipment that is not UL (or equivalent) listed should not be connected in such a manner as to invalidate your home owners insurance.

Good luck,
Russ

[Mike90250]

Each install varys, you may need to set PV for higher voltage for a long DC run, then MPPT becomes more attractive, $300 in wire goes pretty fast. At $350, rewire panels to series, use smaller wire & MPPT controller.

[john p]

His system he claims is only ever going to reach 500w thats about 3x175 w panels in parallel at 13v thats an absolute max of 40a. (a figure never likely to be achieved) so #8 wire is more than adequate for that,, and $300 would most unlikely be needed to buy enough cable. so going to a smaller size by raising the panel voltage by going to series is likely to save next to nothing.. and it still likely his super cheap MPPT controler is not much more efficient than a good PWM one and most likely more likely to fail.
I have never tested a cheap chinese MPPT controller that was better than a PWM one .