Solar wiring

[Orchidius]

Hi there,

So I got the panel, got the eco-worthy MPPT charge controller, I'm almost good to go! I'm a bit bummed out by the lack of information on the wiring of the charge controller though.

I'll be doing everything myself, and have read quite a bit about solar installations over the last few months. But I'm still stuck with a few questions.

So the manual pretty much just says "solar connections here -->", "battery connections here -->", "load connections here -->". Period. Obviously I'll need a fuse in the positive lead to the battery, but how big a fuse? And what kind?
Also, will I need a switch to turn the panel off or a contraption (can't think of the name) that prevents current flowing the wrong way at night?

I really would hate to blow anything up in the process of installation, so if I'm missing anything big, please do tell

Ooh, ofc, panel is a 255W one with a max unloaded voltage of 38,3V, batterybank is still to be purchased but will be 12V. MPPT controller is 20A eco-worthy.

[jkindredpdx]

Add a controller and isolator to avoid frying your batteries, ruining your alternator, and discharging at night.


JimK

[sailorboy1]

I wired my controller output to a breaker in the main DC panel as that was easy and made it easy to turn it off. The panel input to the controller I installed a fuse sized to protect the panel (the panel spec sheet gave the size needed). The output breaker size was based on the max current the controller could handle to protect it, which was more than the solar panel could put out and WAY below what the wire could handle. In general breakers/fuses need to be sized to the smaller of the rating of the wiring or the devise being protected.

So for my 290W panel system I have a 20A fuse on the panel output and a 50A breaker on the controller output.

[jkindredpdx]

Call warehousesolar.com. They are really nice people and will help you wire everything correctly


JimK

[Orchidius]

Any input on solar discharge and possibly a diode?

[mitiempo]

Originally Posted by sailorboy1

I wired my controller output to a breaker in the main DC panel as that was easy and made it easy to turn it off.

The controller output should be wired directly to the battery positive post through the appropriate fuse. The run should be kept short. The controller has a set output voltage and if wired through a panel the batteries could be getting a lower voltage than intended. Even 3% voltage drop starting at 14.4 at the controller ends up being under 14 volts.

[sailorboy1]

Originally Posted by mitiempo

The controller output should be wired directly to the battery positive post through the appropriate fuse. The run should be kept short. The controller has a set output voltage and if wired through a panel the batteries could be getting a lower voltage than intended. Even 3% voltage drop starting at 14.4 at the controller ends up being under 14 volts.

You can not seriously be trying to say my system that has been working great for 2 years is wrong and expect me to believe you. I don't have a 3% drop because I know how to size wiring.

[socaldmax]

Originally Posted by Orchidius

Hi there,

So I got the panel, got the eco-worthy MPPT charge controller, I'm almost good to go! I'm a bit bummed out by the lack of information on the wiring of the charge controller though.

I'll be doing everything myself, and have read quite a bit about solar installations over the last few months. But I'm still stuck with a few questions.

So the manual pretty much just says "solar connections here -->", "battery connections here -->", "load connections here -->". Period. Obviously I'll need a fuse in the positive lead to the battery, but how big a fuse? And what kind?
Also, will I need a switch to turn the panel off or a contraption (can't think of the name) that prevents current flowing the wrong way at night?

I really would hate to blow anything up in the process of installation, so if I'm missing anything big, please do tell

Ooh, ofc, panel is a 255W one with a max unloaded voltage of 38,3V, batterybank is still to be purchased but will be 12V. MPPT controller is 20A eco-worthy.

I would recommend a 30 A fuse by the battery. Keep all cable runs as short possible, use 8 or 6 awg wire. Make sure you connect the battery first and solar panels last, like the manual says. Because of that, I would not install a switch between the controller and batteries, it may damage the controller.

After you get it hooked up and running, test the system at night by disconnecting one of the solar panel wires at the controller and testing for current flow. I'm pretty sure there's no current flow at night.

[GILow]

I have a pretty similar setup to yours, 280 watts of solar, with a Votronic regulator.

The regulator has it's own (40 amp) fuse to the battery side, so I did not have to worry about that. I did wire it straight back to the battery bank, via the main battery isolator switch, so that it can charge the house bank even if the main house bank switch is off. I used AWG 8 wire for that run, and kept it short, about 100mm (4 inches) of cable from the regulator to the isolator switch and bus. The current from the regulator does travel through the main battery monitoring system so it forms part of the overall equation of power use/replenishment on the boat.

For the panel run I used AWG 9 wire and a 20 amp fuse, though with the panels wired in series, maximum current is only 8 amps.

The setup is very new, and I have not yet had full power from the panels to test the voltage loss on the main feed from the panels to the regulator, but according to the wire size calculators, I should have a power loss of under 2%. I would say the power lost between the regulator and the batteries is negligible.

I hope that helps.

Edit: One more thing... my regulator does not have a load circuit. I didn't want one as there is no advantage in my setup to have a very limited load that is not part of the main battery power auditing system. I am not sure of your needs but I would surprised if you found a use for the load circuit either. Most boats I have looked at just disregard the load circuit on the regulator altogether.


Matt

[Hartleycruiser]

Orchidius

Most solar panels have diodes fitted check inside the connection box .

Greg

[barnakiel]

Match the fuses to the CABLES (not to the expected current of the application nor the current on the panels). Fuses on battery side: at the battery. Fuses on the solar side: at the solars (or none, quite often).

b.

[Seadaddler]

My controller instructions said to add a switch both sides of the controller
and so I used blue sea circuit breakers on both sides one near batteries and one going to the solar panels.
I can shut power to batteries and shut power from panels,when working on wiring cover the panels or wait for night time.
Nick

[mitiempo]

Originally Posted by sailorboy1

You can not seriously be trying to say my system that has been working great for 2 years is wrong and expect me to believe you. I don't have a 3% drop because I know how to size wiring.

What gauge wire and what distance there and return?

I do not run any charging through a panel or battery switch. Direct to the batteries.