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I'm planning to setup a smaller 800W off-grid solar panel system for my weekend cottage in Western Europe.

I already bought the necessary parts, cables, and accessories, here's my design sketch for this off-grid solar panel system:

Solar panel system diagram

Parts:

  • Batteries: 4x 120Ah 12V BIG Professional Solar DC
  • Solar Panels: 8x 100W 12V Renogy Monocrystalline (compact design version)
  • Charge Controller: EPEVER Triron 4215N 40A 150V MPPT 12/24VDC + EPEVER MT50 Remote Control
  • Inverter: Novopal 3000W 24V Pure Sine Voltage Converter
  • 1x 150A ANL Fuse (between the battery bank and the inverter)
  • 2x 15A Inline Solar Panel Fuse (for the 2 clusters of 400W solar panels)
  • 1x 15A 500V DC Curcuit Breaker (between the solar panels and the charge controller)
  • 1x 40A 500V DC Curcuit Breaker (between the charge controller and the battery bank)
  • necessary Y plugs, 2x 10m of standard 10AWG (6mm2) solar cable extension cords and thick 3/0AWG (95mm2) cables for the batteries and the inverter

Short Plan Summary:

  • 1.: connect the 4 batteries in series AND parallel getting 24V of 240Ah
  • 2.: connect this battery bank with the 3000W 24V inverter, there's a 150A ANL fuse between the inverter and the battery bank
  • 3.: connect the EPEVER charge controller with the battery bank, there's a 40A 500V DC circuit breaker between them
  • 4.: create 2 clusters of 400W solar panels in series (20V 5A => 80V 5A), then connect these 2 clusters with 15A inline fuses, thus getting the 800W solar panel array (2x 80V 5A => 80V 10A) - the EPEVER charge controller can handle only 150V Max PV
  • 5.: connect the solar panel array to the charge controller, there's a 15A 500V DC circuit breaker between the solar array and the charge controller

Questions:

  • 1.: As the EPEVER charge controller can handle only 150V Max PV, the solar panel array consists of 2 clusters of 400W solar panels in series, then connect them in parallel. Is this a correct way to connect these 8x 100W solar panels to my EPEVER charge controller in my case?
  • 2.: Are the 15A inline fuses, the 15A, and 40A circuit breakers, and also the 150A ANL fuse correct/applicable for this system?
  • 3.: When the solar system is fully connected, is there a recommendation for where to connect the inverter to the battery bank to? Connect closest to the charge controller (i.e.: connect the inverter cable directly to the battery tab/terminal/bushing where the charge controller connected too), or farthest from the charge controller connection (i.e.: connect the inverter cable essentially the opposite/farthest battery tabs/terminals/bushings)

Any corrections, suggestions, and help is highly appreciated.

3 Answers 3

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This looks like a perfectly valid diagram for a working off-grid solar system.

However, several considerations:

  • Are you really sure you want to use a 24-volt system for 3000W? I would heavily recommend 48 volts for such a big wattage. Note the 95mm2 cabling you planned to use to make 3000W at 24 volts possible is insane.

  • As the solar panels can't provide the full 3000 watts, I would recommend connecting the inverter as close to battery terminals as possible.

  • Note that DC circuit breakers for high voltages and amperages are big and expensive. The reason is that unlike for AC that has 100 or 120 opportunities every second to extinguish an arc, with DC you are essentially handling a welding arc that needs to be extinguished and that won't be easy. I suspect you already noticed this as you are not planning to use a 150 ampere circuit breaker but rather a 150 ampere fuse. However, you could consider using fuses too for the 15 amp and 40 amp applications. Nothing wrong with a fuse, you need to trip a circuit breaker a big honking number of times until it becomes less expensive than a fuse and a fuse box. But maybe with a circuit breaker disconnecting it manually will be easier, to burn a fuse you always need overcurrent, so perhaps there's some merit in using circuit breakers.

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Your plan seems very well researched.

I agree with Juhist that it's best to push the battery voltage up to 48V since you're only using it to run an inverter. This will dramatically reduce wire size for the batteries and fuse sizes as well. I agree, 3/0 copper is bonkers, and it would only make sense if you were going a very short distance.

The way to connect the charge controller to the inverter looks fine. Functionally, the inverter draws from the battery while the solar panels replenish the battery.

I don't know your distances, but the advantage to series wiring the panel is reduced wire size at a given voltage drop on the distance. You know your distances so you know if that's worth paying more for a higher voltage charge controller. #6 copper is painfully expensive; if your nation has product support for aluminum wire, I'd use that where practicable. It's also a lower theft risk.

I wish you had access to North American kit. Circuit breakers rated up to 48 volts DC are available cheap, they are the "QO" line from Square D. They use North America's eccentric system of proprietary circuit breaker panel enclosures, so they only fit a QO panel. Also, larger amp breakers will only be available 2-pole, so you might as well protect both negative and positive, which doubles your protection and near doubles your interrupting power. In Europe, they do business as Schneider, but I don't know if they offer QO breakers in normal or DIN rail form.

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I don't see any problems with the way you want to connect your panels, if you have the cables and interconnects sorted out.

If your max power point tracker is like the Epever Tracer4210AN, that big wire won't fit into your connection terminals. You'll need to use 16mm2/6AWG. I've seen folks worry too much about line losses and use huge wire. Anyway, you don't want to buy big expensive wire and not be able to use it.

If you use Aluminum wiring make sure you use anti-oxidant on the wiring ends. Those terminations will get really hot and could burn your house down when corroded. Aluminum oxide corrosion may not look like much but, it has high resistance and will make things dangerously hot.

Your fuses seem fine. Connect the battery fuse within 15cm of the battery.

It will cost you some money but, it might be helpful to use one or two small junction box/control enclosures to put your circuit breakers and interconnect terminal blocks on DIN rail inside, with bushings for the wire pass throughs into it. Make a basic mechanical drawing for how everything will mount inside and leave lots of room for the wiring before you buy the box, terminals and rail. You can mount it all in the box(es) before you go to set up your system.

Just connect the battery, inverter and MPPT all together at terminal blocks. This will keep it convenient. You don't want extra connections. Connections are the biggest problem in wiring.

48V is good because the wiring will be smaller and cheaper. It's also, still less than 50V and is not a lethal shock hazard. 24V is fine, too though.

Good Luck.

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