What charge protector should I use?

gerardrice

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Oct 31, 2021
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Hey guys I’m new to this forum and im
Hoping to learn more about solar. I have (2) 100 watt renogy panels and I have 2 older panels that I got off of a friend they are (2) 75 watt panels so a total of 350 watts total in solar array. I current just have 6 heavy duty commercial batteries that are 100ah each until I can afford solar batteries. I am wondering what is the best charge protector for me? A renogy wonderer 30amp pwm came with the renogy panels when I bought it. Everything I read online says that mppt is way better so I’ve been looking at mppt is renogy rover in the 30amp or the epever 30 amp mppt . Which would you prefer or will I need a mppt at all? Just looking to set up a basic system to run lights, tv , and maybe a small refrigerator later. Any help will be great guys like I said I’m new to this and any info will be awesome .

Cheers
 

Diysolar123

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The reason an MPPT is "almost" always the right choice is that it allows for a large range of input voltage from the panels and can get the maximum amount of power out of your solar panels at any moment.
With pwm solar chargers they are configured to accept a specific input voltage and thats it...
The reason I say "almost" always is that if you only have a single panel and are sure you will never get more it does not matter that much; for anything else get an mppt charge controller with anice wide pov input voltage range.
You have four panels, that means you could put some or all of them in series depending on the input voltage limit of your selected mppt which provides a higher power at a lower current so you can use lower guage copper wires from the panels to the charge controller.
 

gerardrice

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Here are the specs on the 100 watt renogy panels
  • Maximum Power: 100W
  • Maximum System Voltage: 600V DC (UL)
  • Optimum Operating Voltage (Vmp): 18.6V
  • Optimum Operating Current (Imp): 5.38A
  • Open-Circuit Voltage (Voc): 22.3V
  • Short-Circuit Current (Isc): 5.86A
 

Bud Martin

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How about the 75W panels? The spec will affect on how you can combine them with 100W panels, you will not get 350W unless the spec are closely matched since the one with weakest spec will limit the power of the penal with higher spec.
 

gerardrice

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Oct 31, 2021
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Ok here is the specs off of the 75 watt panels

  • Maximum Power: 75Watts
  • Maximum System Voltage: 600V DC (UL)
  • Optimum Operating Voltage (Vmp): 17.0V
  • Optimum Operating Current (Imp): 4.4A
  • Open-Circuit Voltage (Voc): 21.7V
  • Short-Circuit Current (Isc): 4.8A
 

Short_Shot

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Gotta watch that input voltage too.

Now that it's fall my small panels have a hard time meeting the vbat +5v requirement to actually turn my victron on and start charging lol

They are similar voltage to yours, give or take a few tenths.
 

indalecio

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Oct 26, 2021
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I suggest you choose one special charger which has two channel for solar input, so you need not to worry about the current flow from the higher voltage to lower side. But I do not know if you could find such controller. Just have a try.
 

gerardrice

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I don’t understand . If I’m hooking these panels in parralel I will only have to worry about amps right because voltage stays the same ? And in series I have to worry about the voltage but amps stay the same . Just curious
 

Bud Martin

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The Voltage of the parallel connection will be the Voltage of the panel with the lowest Voltage, so in this case it will be 17V.
The power from the 75W panel will be 17Vmp x 4.40Imp = 75W from each 75W panel, the power from 100W panel will be 17Vmp x 5.38A = 91W, so the total power = 75W + 75W + 91W + 91W = 332W.
 

gerardrice

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Wow I didn’t know that! I figured all panels would all work and not loose voltage . So they all have to be the same watt to have no voltage drop. So am I better off selling the older panels and get another 2 100 watt renogy panels? I’m trying to decide how big of a solar system I need for lights , tv and maybe a fridge at a off grid cottage . I know a friend that has 800 watts of panels and each are on there own pwm charge protectors haha I’m trying to tell him they need to be all tied together but in this case he probably would loose alot of voltage. He has (3)100 watt panels (1) 150 watt panel and (1)big 350 watt panel lol
 

Bud Martin

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You are only loosing 18W of power, but in real world you are not going to get 332W (calculated value) either.
Why don't just try out on what you have first?
 

gerardrice

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Oct 31, 2021
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Ok so I’m thinking about a 30 amp mppt controller . Either the epever or the renogy rover. Anyone know which is the best option to go with? Thanks
 

740GLE

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Apr 30, 2021
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Parallel strings are much better with shading so that’s always a plus.
 
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