Solar panel question

[foxxxnick]

I am new to this. I have been looking at 100W panels, comparing panels for most output, do I take the Wattage and divide it by the VMP #to get max. amp output. If this is right, HQST, NewPowa and Renogy all have different VMP #'s which give me different amp #'s. My goal is to either get 2 100W or 1 200W and a MPPT controller. I will use it on the ground so as to maximize sun. How do I compare panels to make the most amps going to battery? Thanks.

 

[Inyo_man]

I'm new to the solar world, but one of the important parts that I've been looking for in a solar panel is the "efficiency" of the panel to produce power. This enables the panel to produce sufficient power in low light situations.
I'm looking at a 200W panel with a 23.5% efficiency rating.
Cheers

 

[rruff]

I am new to this. I have been looking at 100W panels, comparing panels for most output, do I take the Wattage and divide it by the VMP #to get max. amp output. If this is right, HQST, NewPowa and Renogy all have different VMP #'s which give me different amp #'s. My goal is to either get 2 100W or 1 200W and a MPPT controller. I will use it on the ground so as to maximize sun. How do I compare panels to make the most amps going to battery? Thanks.

Amps are irrelevant with MPPT, since it automatically adjusts the volt-amps (ie power) to maximize the input to your battery.

If you want to be able to use a long cord on a remote panel to avoid shade and such, get 24V panels... or wire your 12V in series if you are attaching them together. The wire losses with 24V will be only 1/4 as much. The MPPT will have no problem converting the higher voltage for 12V batteries.

I'm new to the solar world, but one of the important parts that I've been looking for in a solar panel is the "efficiency" of the panel to produce power. This enables the panel to produce sufficient power in low light situations.
I'm looking at a 200W panel with a 23.5% efficiency rating.
Cheers

Efficiency is for minimizing size and maybe weight. Low light performance is something else... but there isn't any magic, as the available power will be reduced if the inputs (solar rays) are reduced. Panels are typically rated at max sun conditions. Performance at low light is hard to come by.

 

[Inyo_man]

Thanks for the clarification, rruff.

Does this sound about right?
"Solar cell efficiency refers to the percentage of sunlight shining on each cell that converts to electricity. The combined efficiency of each cell determines a solar panel’s overall efficiency."

Cheers

 

[fratermus]

do I take the Wattage and divide it by the VMP #to get max. amp output

The Isc number (current, short circuit) in the specs is the max amp output. Imp is current at max power. Because of cell temp derating and other factors, the observed current from the panels will likely be lower than Imp.

How do I compare panels to make the most amps going to battery?

Extracting maximal power power from the array is one of MPPT's defining features. Feed it panel that meets the input spec (input voltage range, most importantly) and it will do the rest. <-- this is why MPPT owners pay 2-3x the price of PWM

Usually MPPT has a quite generous input voltage range but some combo DC-DC/MPPT models have quite restrictive limits that would preclude running the panels in series. Read the specs for all the bits before buying anything.

You didn't ask, but: 200w of panel at retail is typically $200 ($1/W). Used commercial/residential panel is often $0.33/W off craigslist, fb marketplae, etc. 250w is a common size. So 25% more wattage for 58% less money. Food for thought.

 

[Alloy]

I am new to this. I have been looking at 100W panels, comparing panels for most output, do I take the Wattage and divide it by the VMP #to get max. amp output. If this is right, HQST, NewPowa and Renogy all have different VMP #'s which give me different amp #'s. My goal is to either get 2 100W or 1 200W and a MPPT controller. I will use it on the ground so as to maximize sun. How do I compare panels to make the most amps going to battery? Thanks.

I'm new to the solar world, but one of the important parts that I've been looking for in a solar panel is the "efficiency" of the panel to produce power. This enables the panel to produce sufficient power in low light situations.
I'm looking at a 200W panel with a 23.5% efficiency rating.
Cheers

With 12V (<30Vmp) the certificates will be few and far between so wattage can't be used as a guide.

Better off comparing household panels (>30Vmp) that have CEC,UL,ETL certificates.

 

[foxxxnick]

Thanks very much, everyone! I appreciate all of your suggestions.