Proper cable gauge for over paneling

Hello all,

A few days ago I received a new Bluetti eb70s and so far I'm really happy with it. I'm currently eyeing a 12v 200 watt Rich solar panel and I have future plans to over panel in parallel with a second 200 watt panel. I'd like to purchase an 8 gauge 20ft pv cable and it is my understanding that the eb70s won't pull more than 8amps. From what I'm seeing based on an online calculator I've tried I should be safe to pull up to 10amps @ 20ft. Is my understanding correct or am I way off base?

Also for fusing am I correct in assuming that I should put a 10amp fuse just before the eb70s?
Eb70s <--- (barrel to mc4) <---(10amp fuse) <---(20ft 8gauge pv cable)<---(200watt panel)

200 Watt Rich panel
20ft 8 gauge pv wire

FreshRust said:

Hello all,

A few days ago I received a new Bluetti eb70s and so far I'm really happy with it. I'm currently eyeing a 12v 200 watt Rich solar panel and I have future plans to over panel in parallel with a second 200 watt panel. I'd like to purchase an 8 gauge 20ft pv cable and it is my understanding that the eb70s won't pull more than 8amps. From what I'm seeing based on an online calculator I've tried I should be safe to pull up to 10amps @ 20ft. Is my understanding correct or am I way off base?

Also for fusing am I correct in assuming that I should put a 10amp fuse just before the eb70s?
Eb70s <--- (barrel to mc4) <---(10amp fuse) <---(20ft 8gauge pv cable)<---(200watt panel)

200 Watt Rich panel
20ft 8 gauge pv wire

Click to expand...

Safety is one thing efficiency is another. You probably could safely run 10 amps on 14 gauge PV wire but you will lose noticeable watts on the way. 8 Guage is plenty. I would probably do 10 guage if I was going to pack up the panels a lot just for ease of handling the wire, it’s only a 1% efficiency loss between the 2 sizes. When you calculate wire size you need to use the max power voltage (vmp ) from the panels specs not the nominal voltage. I am assuming a 17 volt vmp in my calculations. You only need fuses if you are paralleling more than 2 panels and those fuses go between the panels. A shutoff of some kind is a good idea to avoid damaging connections when you unplug the panel under a load. If the bluetti has a way of turning off the solar input that would work just as well..

I don't plan to leave the panels up unless we're doing something outside or the power is out. So going to 10 gauge makes sense and I won't complain since it'll save us some money. The vmp on the panel I'm looking at is 20.4 and the max voltage input on the eb70s is 28v. Good to know on the fuses, I doubt I'll be running more than 2 panels for now. If I get more I'll either be building a portable power station myself or buying a second eb70s.

Unfortunately the eb70s uses a barrel connector to mc4 for input and there isn't a mechanical switch or breaker on the unit I can flip to disconnect the power. From what I've seen in reviews most just unplug the barrel connector from the unit. However, if there is a better solution I'm all ears.

FreshRust said:

I don't plan to leave the panels up unless we're doing something outside or the power is out. So going to 10 gauge makes sense and I won't complain since it'll save us some money. The vmp on the panel I'm looking at is 20.4 and the max voltage input on the eb70s is 28v. Good to know on the fuses, I doubt I'll be running more than 2 panels for now. If I get more I'll either be building a portable power station myself or buying a second eb70s.

Unfortunately the eb70s uses a barrel connector to mc4 for input and there isn't a mechanical switch or breaker on the unit I can flip to disconnect the power. From what I've seen in reviews most just unplug the barrel connector from the unit. However, if there is a better solution I'm all ears.

Click to expand...

You don’t need a mechanical switch to turn off the solar panel if the bluetti will allow you to turn off the solar from the screen that would be perfectly fine. It’s not the end of the world to disconnect a live circuit of that amperage but every time you do the first unpluged connection will sustain a small amount of pitting from the arc that is created. Unless you use it allot I’m not sure a switch is worth the trouble. If it was me and I had to unplug it live I would unplug it between the solar panels cord and your extension so that I don’t risk damaging the connections on the bluetti itself. Those other connections are easily replaced in the unlikely event you ever have trouble with them.