How to best wire new panels

[Larry12]

Hi. I have 4 new to me 250 watt, 25 volt panels. They are actually putting out 35 volts each in full sun here in Costa Rica. I have wire that I think is 10, but it has no identification on it. It is new, just kept unused for a year. It has a very thick rubber insulation containing 2 wires (white and black, each having the standard flexible plastic insulation. My question: If this wire turns out to be 12 AWG is it ok? I will be running each 2 panels in series to make two groups to parallel together, so total output of the array will be "50 volts" (actually 70 volts in full sun since each panel is giving 35 volts) and 1000 watts). My battery system is 48 volts (four 150 AH 12 volt batteries in series) I run my refrigerator, LED lights, washing machine (mid-day), and 3 Shurflo 2088 RV type water pumps for household use. Thanks in advance for your help.

 

[glandpuck]

Wire that is exposed to the air, meaning not in a conduit, should be PV rated wire. This is usually the wire between panels that goes into a combiner box or disconnect switch, etc and exits in a conduit. PV rated wire is UV resistant and meant to be exposed to sun, salt, etc. Once inside a box or enclosure and a conduit, the wire should be thhn or thwn which is insulated, but not UV resistant. This is usually the wire from the array to the inverter. You only need 12 AWG or 10 AWG size wire for your panels.

 

[Larry12]

I found 100' of #10 in the garage just now but someone said I could just use 12 AWG. That would be easier and less expensive than cutting the other.

I am already running the battery /inverter system through 4 other panels going through a different charge controller.

 

[glandpuck]

Wire for solar panels is not rubber coated.

 

[Larry12]

They are 12 AWG. I found the numbers. Fine strand.

 

[Larry12]

Wire for solar panels is not rubber coated.

Ok, thanks. So I will use conduit. I originally bought it for a long run to a water pump and never used it.

 

[littleharbor2]

Those 60 cell solar panels are not considered 24 Volt nominal. They're considered 20 Volt nominal. That being said, you want to wire all four of them in series if you want to charge a 48 Volt battery bank Hopefully your charge controller can handle the voltage Otherwise, I'd wire 3 in series and keep one off to the side, but you'd be better off wiring all four in series

 

[Larry12]

Those 60 cell solar panels are not considered 24 Volt nominal. They're considered 20 Volt nominal. That being said, you want to wire all four of them in series if you want to charge a 48 Volt battery bank Hopefully your charge controller can handle the voltage Otherwise, I'd wire 3 in series and keep one off to the side, but you'd be better off wiring all four in series

Yes they are 60 cell. The specs only tell me:
Pmax 250 watt.
Voltage at pmax 30.2 volts.
Current at pmax 8.28 amps
Open circuit voltage: 37.8 volts.
With these specs, is it certain that I have to wire all parallel for my 48 volt system? That will put me close to 100 volts. Sounds logical to me though, now that you suggested it because I guess I have a lot of rain and clouds at times potentially lowering my voltage. How do I protect myself wiring series all the way? I'm wearing kitchen rubber gloves. They might melt! I bought mc4 connecters but they included short male and female metal ends. I may have to wire with bare wire strands wired together. We live in the bush and a trip to the capital city where they sell MP4's is a pain.

 

[Larry12]

Those 60 cell solar panels are not considered 24 Volt nominal. They're considered 20 Volt nominal. That being said, you want to wire all four of them in series if you want to charge a 48 Volt battery bank Hopefully your charge controller can handle the voltage Otherwise, I'd wire 3 in series and keep one off to the side, but you'd be better off wiring all four in series

I think I will parallel 3 and use the fourth for a water heater experiment. Each panel tested 37 volts in the midday sun and my charge controller max is 150 volts. Thanks for the suggestion.

 

[littleharbor2]

Series wire the 3. You're a bit confused with your terminology I would suggest you study up before you start messing around with wiring things. Use a multi meter to check polarity. Make sure all the positives are marked with red tape. From the sounds of your limited availability you could always just ghetto wire it, twisting wire together using wire nuts and electrical tape But do yourself a favor, get a multimeter, check polarity, check voltage series wiring is plus to minus, plus to minus. Not all positives together Negatives together

 

[Larry12]

Series wire the 3. You're a bit confused with your terminology I would suggest you study up before you start messing around with wiring things. Use a multi meter to check polarity. Make sure all the positives are marked with red tape. From the sounds of your limited availability you could always just ghetto wire it, twisting wire together using wire nuts and electrical tape But do yourself a favor, get a multimeter, check polarity, check voltage series wiring is plus to minus, plus to minus. Not all positives together Negatives together

Thanks. What terminology am I messing up on? I do know the difference between series and parallel. I have four 12 volt batteries in series, so that is a 48 volt "battery". I have 4 other 12 volt panels in series already working for 3 years. I have a multimeter and do test for polarity. I did figure out how to make my MP4 kit connections yesterday, was green with that. May run out and have to ghetto wire to finish.

 

[Larry12]

Series wire the 3. You're a bit confused with your terminology I would suggest you study up before you start messing around with wiring things. Use a multi meter to check polarity. Make sure all the positives are marked with red tape. From the sounds of your limited availability you could always just ghetto wire it, twisting wire together using wire nuts and electrical tape But do yourself a favor, get a multimeter, check polarity, check voltage series wiring is plus to minus, plus to minus. Not all positives together Negatives together

 

[Larry12]

My charge controller will take up to 150 volts. I tested the panels at midday and the multimeter showed 37 volts plus ot minus a volt. With all four in series I would possibly go slightly over 150 volts at times. I mentioned being close to 100 volts based on what you said, that these are actually nominal 20 volt panels.

 

[Larry12]

My charge controller will take up to 150 volts. I tested the panels at midday and the multimeter showed 37 volts plus ot minus a volt. With all four in series I would possibly go slightly over 150 volts at times. I mentioned being close to 100 volts based on what you said, that these are actually nominal 20 volt panels.

 

[Larry12]

3 panels in series will work great. Thanks for helping me think this through, littleharbor2 !

 

[littleharbor2]

Thanks. What terminology am I messing up on? I do know the difference between series and parallel. I have four 12 volt batteries in series, so that is a 48 volt "battery". I have 4 other 12 volt panels in series already working for 3 years. I have a multimeter and do test for polarity. I did figure out how to make my MP4 kit connections yesterday, was green with that. May run out and have to ghetto wire to finish.

This, "With these specs, is it certain that I have to wire all parallel for my 48 volt system? That will put me close to 100 volts."
Also, MC-4 is the correct name of the connectors.

 

[littleharbor2]

The reason 60 cell panels are called 20 Volt nominal is if you look at the VMP rating of the panel, you'll see it's about 30 volts. Well with that 30 Volt output, when the weather gets hot, that 30 volts will be considerably lower and it won't be enough to properly charge and or equalize lead acid batteries. So hence the terminology 20 Volt nominal. You need a 72 Panel to be considered a 24 Volt nominal panel because it's got about a 36 to 37 Volt VMP , which even when degraded by heat, is still high enough to charge and equalize lead acid batteries.
Nowadays with MPPT charge controllers, especially the high voltage Input models The output voltage of your panels is fairly irrelevant. It's all a matter of just series wiring up to the voltage that works best for you but historically in the early days of solar, that's where the 12 Volt or 24 Volt panel Got its name