Fuse in a solar circuit?

[chenderson1965]

I’ve just changed the solar controller on one of my panels from a basic pwm type to a Victron MPPT. There was an existing inline fuse in the +ve wire from the controller to the battery - which I discovered because it had blown (who knows how long ago!). The fuse was rated at 10A. I’m pretty certain the panel is 150w.

A couple of questions then:-

- Do I need the fuse now I have a quality controller regulating the current to the battery? (There is a fuse in the regulator too)
- if I do, what value should I use? (By my calculations 10A is a bit low)

Thanks a lot.

Chris

 

[Lenny HB]

Always wise to have a Fuse if there is not one in the regulator, 15 amp will be Ok.

 

[funflair]

Hi Chris

Likewise a think 10a is a touch low, you should actually have a fuse at both ends in my view as if there was a short in the cable it is actually fed with power potentially from both ends.

 

[PeteH]

I think, (never always a good idea), But if you are sure its 150W? then the theoretical Voltage at full output would be 15V? (assuming 10A fused.) Solar panels rarely produce their rated output. But a fuse would protect against spikes. BTW I often see in excess of 20Volts from the panel(s) (200W). Before the controller.

 

[autorouter]

- Do I need the fuse now I have a quality controller regulating the current to the battery? (There is a fuse in the regulator too)
- if I do, what value should I use? (By my calculations 10A is a bit low)

Any wire connected to a battery should have a fuse near the battery end. Its purpose is to protect against overheat/possible fire if there's damage to the wire and it shorts to itself or the metal bodywork.

Realistically the controller is very unlikely to output more than 10 amps with a 150W panel , so I would use the next size up which would be 15A.

Unlike batteries, solar panels do not generate large extra currents if they are shorted, so the fuse is not really for protecting the panels or the controller.

^{_{Subscribers  do not see these advertisements}}

 

[Reallyretired]

Also a fuse between panel and controller is useful as an easy way to isolate the panels. I use 30A circuit breakers which are even easier. Actually 3 of them one between panels and controller and two between batteries and controller one at each end.

 

[PeteH]

I currently have a volt meter, wired to show the Output voltage from the Solar Panels. I often "see" 19 or 20 volts. and during recent "Sunshine" It was showing 24Volts at one point. I suspect the rated voltage to be 48V?. But as I did not buy nor fit them, that I cannot confirm. I have been contemplating swapping it for a Volt/Amp combination Read out.

 

[funflair]

I currently have a volt meter, wired to show the Output voltage from the Solar Panels. I often "see" 19 or 20 volts. and during recent "Sunshine" It was showing 24Volts at one point. I suspect the rated voltage to be 48V?. But as I did not buy nor fit them, that I cannot confirm. I have been contemplating swapping it for a Volt/Amp combination Read out.

I would think that the 24v is about the max of the panel and it would be showing when the batteries were full so very little demand to pull down the panel voltage.