Need help with wiring and fuses

[Alohasun]

So still learning a lot about solar. I'm now reaching into uncharted waters with 4 panels. I'm hoping to hook up in parallel yeah? Can someone help me understand the connections I would need and fuses, how big and where?

System:
4 245w 37.3V 30.7Vmp 7.98Imp panels
60a controller
4 6v 210ah batteries wired for 24v
800w 24v inverter

I could run a mc4 branch from 2 panels at 30a 10awg
and wire those 2 sets with mc4 branch 40a 8awg to controller right?
and then fuse each panel, the controller, bank, and inverter?

Or am I off a bit?

[Mike90250]

So, you are into the wattage range where you should be using a 40A MPPT controller. Wiring 4 panels in series to keep your wire gauge down, is going to set you too close to the 150V threshold for killing your controller, so you will need to run panels 2S2P (2 in series, 2 in parallel giving you 61V @ 16A )

A PWM controller with all panels in parallel ( I hope you have not bought one ) will not have enough voltage, at 31v, to loose a couple volts to hot (being baked in the sun) and drop a couple volts in the controller, to be able to properly charge @ 30V and EQ 32V the batteries.

If nobody else has a sketch, I'll make up one in the AM

[Alohasun]

So basically the attached picture.
20a fuse on each series pos line yeah?
Match fuse size with controller on pos line yeah?

[SunEagle]

So basically the attached picture.
20a fuse on each series pos line yeah?
Match fuse size with controller on pos line yeah?

OK. So if you used the 2s2p configuration with your 4 x 245 watt panels, your circuit would be 2 x the Vmp value of 30.7v or 61.4v and 7.89amps for each parallel string.

The 61.4v is enough to charge a 24v battery system but with a PWM CC you can maybe 16 amps (2 x 7.89 = 15.78a) of charging or a C/13 charge rate which would be not enough for a 24V 210Ah battery system.

If the CC was an MPPT then you could get 40 amps of charging (4 x 245w / 24v = 40.8a) or a C/5.25 charge rate which would be too high for FLA batteries and almost too high for AGM type batteries.

With only 2 strings of panels you are not required to install any fusing between the panels and CC but if you wanted to install fuse you might be able to go with a 10amp for each string since the Imp = 7.89a

[Alohasun]

OK. So if you used the 2s2p configuration with your 4 x 245 watt panels, your circuit would be 2 x the Vmp value of 30.7v or 61.4v and 7.89amps for each parallel string.

The 61.4v is enough to charge a 24v battery system but with a PWM CC you can maybe 16 amps (2 x 7.89 = 15.78a) of charging or a C/13 charge rate which would be not enough for a 24V 210Ah battery system.

If the CC was an MPPT then you could get 40 amps of charging (4 x 245w / 24v = 40.8a) or a C/5.25 charge rate which would be too high for FLA batteries and almost too high for AGM type batteries.

With only 2 strings of panels you are not required to install any fusing between the panels and CC but if you wanted to install fuse you might be able to go with a 10amp for each string since the Imp = 7.89a

Yeah CC is MPPT. Thank you for reply.

[Sunking]

No fuses are required or needed for panels in 2S2P configuration. Panels are current sources, not voltage sources. So with just 2 parallel strings, it is not possible to generate enough current to ever operate a fuse.

[Alohasun]

If the CC was an MPPT then you could get 40 amps of charging (4 x 245w / 24v = 40.8a) or a C/5.25 charge rate which would be too high for FLA batteries and almost too high for AGM type batteries.

What is the remedy to a better c rate for FLA batteries?
less panel?

[Sunking]

What is the remedy to a better c rate for FLA batteries?
less panel?

C/10 to C/8 which is controlled by the right panel wattage paired with the right controller.

With MPPT Controllers is pretty simple to get panel wattage in the ball park. A 200 AH battery requires 20 to 25 amps. Wattage = Battery Voltage x Charge Amps so a 48 volt battery is 50 volts x 20 amps = 1000 watts, up to 1250 watts. Unforrtunately you have a PWM controller, thus not enough panel wattage to get you to minimum requirements.

[Mike90250]

Advanced MPPT controllers you can also set a max charge rate. So on a cloudy day, normally excess panels help your harvest

[Alohasun]

C/10 to C/8 which is controlled by the right panel wattage paired with the right controller.

With MPPT Controllers is pretty simple to get panel wattage in the ball park. A 200 AH battery requires 20 to 25 amps. Wattage = Battery Voltage x Charge Amps so a 48 volt battery is 50 volts x 20 amps = 1000 watts, up to 1250 watts. Unforrtunately you have a PWM controller, thus not enough panel wattage to get you to minimum requirements.

CC is MPPT. Battery is 24v

[Sunking]

CC is MPPT. Battery is 24v

OK wire panels 2S2P. That wil get you roughly 40 amps of peak charge current at noon if the batteries are real low. A bit high, just keep an eye on water levels.

[Alohasun]

OK wire panels 2S2P. That wil get you roughly 40 amps of peak charge current at noon if the batteries are real low. A bit high, just keep an eye on water levels.

Appreciate it.