Newbie keeps blowing a fuse

I'm an electrical novice trying to put together a milk crate battery system with solar for use with my CPAP when the power goes out. Everything was working fine until I attached the solar panel cables to the solar controller. Now I keep blowing 20AMP fuses and it is not apparent why. I have attached a picture of the system. Any suggestions? Thanks.

Houstonchef said:

I'm an electrical novice trying to put together a milk crate battery system with solar for use with my CPAP when the power goes out. Everything was working fine until I attached the solar panel cables to the solar controller. Now I keep blowing 20AMP fuses and it is not apparent why. I have attached a picture of the system. Any suggestions? Thanks.

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My first instinct is to say due to inrush current, but that is a guess.

Which part of the circuit is the fuse protecting? a wire that runs from a to b, presumably. a = battery, what is the device at b?

I'm assuming you are talking about the (currently removed) fuse hooked up to the charge controller.

It's hard too see in the picture but it looks like the charge controller has 20A output. So a 20A fuse is too small. The approach is to choose a wire that can safely handle the amps. Then you pick a fuse size to protect the wire. I would use 14AWG (or thicker) and a 25A fuse. The 14AWG wire can easily handle the 20A and the 25A fuse will protect the wire while avoiding nuisance trips from the 20A output of the charge controller.

You should post more details about what size everything is if my assumptions don't actually match what you have.

DerpsyDoodler said:

My first instinct is to say due to inrush current, but that is a guess.

Which part of the circuit is the fuse protecting? a wire that runs from a to b, presumably. a = battery, what is the device at b?

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The fuse is protecting the Bat+ on the solar controller and the battery +.

Sounds like rmaddy is dead on.

BTW, how much power are the solar panels?
It is is 20A charger so the fuse between charger needs to be higher than 20A as suggested by others, is user manual should indicate what the fuse size and the wire gauge should be.

Houstonchef said:

I'm an electrical novice trying to put together a milk crate battery system with solar for use with my CPAP when the power goes out. Everything was working fine until I attached the solar panel cables to the solar controller. Now I keep blowing 20AMP fuses and it is not apparent why. I have attached a picture of the system. Any suggestions? Thanks.

Click to expand...

As your system stands, it looks like you should connect your charge controllers positive directly to the battery.

You could also get a bus bar and install a breaker between the bus bar and battery. Then connect all your positives to the bus bar.

KeiJon said:

As your system stands, it looks like you should connect your charge controller positive directly to the battery.

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But then there is no fuse between the SCC and the battery.

That's why I said as your system stands now. If you use a bus bar and breaker you won't need a fuse. The breaker will act as the fuse and an on and off switch.

BTW, since right now you do not have the new fuse installed yet, you should not have the PV panels connected to the SCC until the fuse is replaced first since you may damage the SCC if you have panels connected without the battery connected to the SCC first.You may want to have DC breaker or removeable fuse holder on the PV so you can disconnect the PV panels from the SCC first.