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24v panel vs 12v panel

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skellator

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I am trying to understand how these panels would effect my setup.

I have a 12v setup. But I like the 1 panel 300w setup by renogy: https://www.renogy.com/300-watt-24-volt-monocrystalline-solar-panel/

I'd rather have one panel vs three 100 watt panels or two 150s etc... those panels are 12v.

Are there any efficiency differences between running a 24v panel on a 12v setup?

So it would be something like this 24v panel:
www.renogy.com

4pcs 320 Watt Monocrystalline Solar Panel

Primarily used for residential and commercial purposes, rooftop solar power systems are the perfect way to decrease an electric bill. Also great for large off-grid systems, the 320W Monocrystalline Panel can be used in multi-panel solar arrays for cabins and sheds.
www.renogy.com www.renogy.com
with a MPPT charge controller, and a lithium battery 12v

VS running three 12v panels like this: https://www.renogy.com/100-watt-12-volt-monocrystalline-solar-panel-compact-design/
with the same MPPT charge controller and lithium battery 12v
 
Panels have multiple cells connected in series. Voc is roughly 0.62v per cell and Vmp is roughly 0.53v per cell.

36,60, and 72 cell panels are standard common number of cells per panel. You have to be careful buying panels with less then 36 series cells as they may not have enough overhead voltage to run a MPPT controller for a 12v battery setup. For mono cells, this has been a trend by panel manufacturers to cut cost. A 32 cell panel will not operate a MPPT controller reliably for 12v battery, especially when they get hot in the sun.

As to how many in series is too many, that depends on maximum input voltage of MPPT controller. The one you have shown is a 60 cell panel. Voc will be about 37.5v at 25 degs C. It should be okay for just about any MPPT controller to a 12v battery. Each cell has a temp change of about -2.1 mV per deg C. (higher temp means lower voltage) For MPPT controller max input voltage you have to be careful on cold weather the Voc will be at its highest value.

The most common cell size is M0 designation and is 156 x 156 mm in size. Mono panels can be made from cut cells, either half or even a third of a cell. Silicon cells produce about 35 mA to 40 mA per square centimeter, or about 8.5 to 9.5 amps per full M0 cell size.

A quality factor to be aware of is called fill factor (FF). Is it (Vmp * Imp) / (Voc * Isc). It is typically in range of 0.75 to 0.88 with higher being better.

Just be aware 300+ watt panels get big and a bit heavy. Typically have to ship by truck freight.
 
Last edited:
Setup #1:
PANEL
www.renogy.com

4pcs 320 Watt Monocrystalline Solar Panel

Primarily used for residential and commercial purposes, rooftop solar power systems are the perfect way to decrease an electric bill. Also great for large off-grid systems, the 320W Monocrystalline Panel can be used in multi-panel solar arrays for cabins and sheds.
www.renogy.com www.renogy.com
CONTROLLER
www.renogy.com

Rover Li 40 Amp MPPT Solar Charge Controller

Buy Renogy's Rover 40 Amp MPPT Solar Charge Controller. Pair it with our BT-1 the BT app through bluetooth and you can monitor and adjust your solar system directly from your phone. Our Rover also comes covered in a die-cast aluminum exterior. This allows for safe heat dissipation along with...
www.renogy.com www.renogy.com
BATTERY
www.renogy.com

12V 100Ah Smart Lithium Iron Phosphate Battery

Renogy's smart lithium iron phosphate lifepo battery enables auto-balance among parallel-connections. This 12v lithium ion battery suits for caravan or marine.
www.renogy.com www.renogy.com

Setup #2
Setup #1:
PANEL
3 of these panels: https://www.renogy.com/100-watt-12-volt-monocrystalline-solar-panel-black-frame/
CONTROLLER
www.renogy.com

Rover Li 40 Amp MPPT Solar Charge Controller

Buy Renogy's Rover 40 Amp MPPT Solar Charge Controller. Pair it with our BT-1 the BT app through bluetooth and you can monitor and adjust your solar system directly from your phone. Our Rover also comes covered in a die-cast aluminum exterior. This allows for safe heat dissipation along with...
www.renogy.com www.renogy.com
BATTERY
www.renogy.com

12V 100Ah Smart Lithium Iron Phosphate Battery

Renogy's smart lithium iron phosphate lifepo battery enables auto-balance among parallel-connections. This 12v lithium ion battery suits for caravan or marine.
www.renogy.com www.renogy.com
 
RCinFLA said:
Panels have multiple cells connected in series. Voc is roughly 0.62v per cell and Vmp is roughly 0.53v per cell.

36,60, and 72 cell panels are standard common number of cells per panel. You have to be careful buying panels with less then 36 series cells as they may not have enough overhead voltage to run a MPPT controller for a 12v battery setup. For mono cells, this has been a trend by panel manufacturers to cut cost. A 32 cell panel will not operate a MPPT controller reliably for 12v battery, especially when they get hot in the sun.

As to how many in series is too many, that depends on maximum input voltage of MPPT controller. The one you have shown is a 60 cell panel. Voc will be about 37.5v at 25 degs C. It should be okay for just about any MPPT controller to a 12v battery. Each cell has a temp change of about -2.1 mV per deg C. (higher temp means lower voltage) For MPPT controller max input voltage you have to be careful on cold weather the Voc will be at its highest value.

The most common cell size is M0 designation and is 156 x 156 mm in size. Mono panels can be made from cut cells, either half or even a third of a cell. Silicon cells produce about 35 mA to 40 mA per square centimeter, or about 8.5 to 9.5 amps per full M0 cell size.

A quality factor to be aware of is called fill factor (FF). Is it (Vmp*Imp) / (Voc * Isc). It is typically in range of 0.85 to 0.88 with higher being better.

Just be aware 300+ watt panels get big and a bit heavy. Typically have to ship by truck freight.
Click to expand...

So in summary it sounds like unless I want to get super scientific it will charge and function well?
 
skellator said:
Setup #1:
PANEL
Click to expand...
Okay so you are not really “adding” a 300w panel to an existing system...

I think having bigger and fewer panels is a good thing. Especially if not moving them around often.
That is a large SCC for 300w panel(s) and 100ah battery. It will accept another panel and battery in the future should tou need them though.
That should be a nice little setup. You did not specify your use or energy consumption needs so cannot comment on sizing.
 
As others have said, that 60 cell panel will work fine with at least a 25A MPPT charge controller for a 12V battery. But I have to say my pet peeve, despite what Renergy calls it, that is a 20V solar panel, not a 24V panel. A 72 cell panel is a 24V panel. In the hot weather, it won't charge a 24V battery bank well. They drive me nuts, it's fine for 12V systems, but bad for 24V, not high enough voltage.
 
I went from three 100w 17v Renogy panels to one 327w 54v Sun power panel for my 12v system. So much more efficient and easier. ?
 
skellator said:
Are there any efficiency differences between running a 24v panel on a 12v setup?
Click to expand...
The biggest 'penny drop' knowledge you need to understand this is twofold:
  1. MPPT solar charge controllers effectively isolate the output from the input. In other words, if you have a 12V battery system, you could well have 1,000V or a Million Volts on the PV side of the SCC (OK, exaggerating a little there...).
  2. A "12V" or "24V" solar panel is not a 12V or 24V panel, this is just a marketing term used to help newbies select unfamiliar components. In reality, a "12V" panel will usually output around 21.6V i.e. Voc = 21.6V, and a "24V" panel will usually output around twice that, though their internal cells connections make this more variable, but is doesn't matter because of point (1.) !!
In your case, this 300W panel outputs 38.8V (yes, even though it is marketed as a "24V" panel), so 38.8V would exist on the PV side, but your SCC will then convert this down to whatever your battery needs e.g. 12V / 24V nominal. Your SCC supports up to 100V on the PV-side so you could, in theory, connect up to two of these panels in series for an array Voc of 77.6V (remember PV-side is independent of battery-side) and that would still be OK to charge a 12V battery.

Make sense?
 
Thanks, Tictag, I was about to ask that question myself as my PIP-2424LV-MSD appears to isolate the two inputs.
 
tictag said:
  1. In reality, a "12V" panel will usually output around 21.6V i.e. Voc = 21.6V
Click to expand...

Unless you are in West Texas -- its 108 degrees by noon -- and your 12V panel rated at 21.6 is STRUGGLING to clear 14V due to the heat ....and the panel is literally hot enough to cook an egg on .... to mess with the techs back at the monitoring station I love to take the fire hoses out here and spray water on the small solar farms we have and watch the amperage jump through the roof ... they STILL haven't figured out what causes the system to spike off the chart at times ... LOL .... but honestly the panels are so hot you have to wear thermal gloves to work with them .... looking forward to winter where it drops to a low of 70 .... LOL
 
wow! I live in California and it was 108F yesterday and expected to reach 106F today. So since my PIP-2424LV-MSD controller/inverter can handle easily 48v array system, I better think about using 48v array vs 24v array.
 
ghostwriter66 said:
Unless you are in West Texas -- its 108 degrees by noon -- and your 12V panel rated at 21.6 is STRUGGLING to clear 14V due to the heat ....and the panel is literally hot enough to cook an egg on .... to mess with the techs back at the monitoring station I love to take the fire hoses out here and spray water on the small solar farms we have and watch the amperage jump through the roof ... they STILL haven't figured out what causes the system to spike off the chart at times ... LOL .... but honestly the panels are so hot you have to wear thermal gloves to work with them .... looking forward to winter where it drops to a low of 70 .... LOL
Click to expand...
Interesting. If I ever get to build an off grid house I will definitely set up a roof sprinkler system for the solar panels. My grandfather lived in Florida and had a patio with a sprinkler system for the roof. It did a good job of cooling off the patio.
 
[/QUOTE]
If you're going to use a MPPT controller, you must make sure that the panel delivers
SolarQueen said:
As others have said, that 60 cell panel will work fine with at least a 25A MPPT charge controller for a 12V battery. But I have to say my pet peeve, despite what Renergy calls it, that is a 20V solar panel, not a 24V panel. A 72 cell panel is a 24V panel. In the hot weather, it won't charge a 24V battery bank well. They drive me nuts, it's fine for 12V systems, but bad for 24V, not high enough voltage.
Click to expand...

There's a thread elsewhere in the forum that discusses how the Electrodacus & a PWM controller (actually a PWM relay) was better than a MPPT on 60 cell panels.
 
Freep said:
Interesting. If I ever get to build an off grid house I will definitely set up a roof sprinkler system for the solar panels. My grandfather lived in Florida and had a patio with a sprinkler system for the roof. It did a good job of cooling off the patio.
Click to expand...
Great idea, but here in my area of California, we are prone every 4 to 6 years to have a 2 drought. It's been 5 years since the last one and expects one later this summer where they will force us to water ration up to 40% of last year's usage. - That really sucks!
 
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