Solar question 2

[cagey]

Should I put a fuse and or a switch in the circuit between panel, controller and battery, if so where please, instinctively I want to but I don’t see it specified anywhere I’ve read.
Thanks
Keith

 

[vyv_cox]

Definitely. As close to battery as possible. A couple of years ago we watched a boat burn to the waterline, apparently the result of adding unfused solar panels.

 

[PaulRainbow]

Should I put a fuse and or a switch in the circuit between panel, controller and battery, if so where please, instinctively I want to but I don’t see it specified anywhere I’ve read.
Thanks
Keith

No need for a switch, or for a fuse between the controller and the panel, but you need a fuse between the battery and the controller, as Vyv said, as close to the battery as possible.I'd fit a blade fuse, rated for a little more than the max panel rating, but less than the cable rating.

 

[Richard10002]

Not a bad idea to have a switch between panels and controller. Makes it easy to deal with disconnecting the controller before the batteries, and connecting the batteries before the controller. With no switch, if working on the system, it is tempting to disconnect the batteries without disconnecting the panels.

 

[William_H]

The reason for the fuse between the controller and the battery is the risk that current can flow from the battery via wiring to a short in the controller or wiring. Hence fuse rating should be in excess of any expected charge current but less than the max the wiring can carry before getting too hot. As said put fuse as close to battery as possible as any wiring from battery to fuse will not be protected. Bearing in mind that this circuit will be live when all else is isolated and you have left the boat. olewill

 

[thesaintlyone]

I have a blade fuse on the positive side between battery and MPPT controller the positive wire is split with the blade fuse forming the connection

 

[cagey]

Thanks everyone for the help
Keith

 

[vyv_cox]

Not a bad idea to have a switch between panels and controller. Makes it easy to deal with disconnecting the controller before the batteries, and connecting the batteries before the controller. With no switch, if working on the system, it is tempting to disconnect the batteries without disconnecting the panels.

I was not sure what the problem is here but I think I have thought it through. I have no switch between controller and panels but have disconnected or replaced domestic batteries many times without any problems. I am aware that connections to the controller need to be made in the correct order. However, my Sunworks is a dual bank model, so presumably the starter battery is maintaining the supply to it when the domestic bank is disconnected.

 

[noelex]

A fuse or circuit breaker between the controller and the batteries is important.

The solar equipment suppliers also specify a fuse or circuit breaker between the panels and the controller. It is difficult to understand why this is necessary, I have never heard a satisfactory explanation. Nevertheless a switch between the panels and and controller is useful, especially with high voltage panels. High DC voltages deserve some respect. If installing a switch it may as well be a circuit breaker especially as switches with a high voltage DC rating are not very common.

This is my set up, but this is large (1000w) high voltage (60v+) three panel installation. Something simpler would be fine for most boats. The circuit breakers on the left are between the panels and the controller and the circuit breakers on the right are between the controllers and the battery (with one extra). The black box in the middle is a shunt that reports the output of each panel:

 

[vyv_cox]

When I worked in research the rules on electrical connections were that AC mains and DC greater than 50 volts had to be done by an electrician. DC above that level can be nasty.