Solar fuse size?

[Lady_Trish]

Hello!

 

What amp fuse would I need on a 12v system between my MPPT controller and the batteries with 500w of solar?

 

Upgrading from 250w, which currently has 30A fuse

 

:-)

[nicknorman]

Hello!

What amp fuse would I need on a 12v system between my MPPT controller and the batteries with 500w of solar?

Upgrading from 250w, which currently has 30A fuse

:-)

You should be OK with a 50A fuse but also, be sure the cable can take 50A without overheating.

[Lady_Trish]

I have a fuse already that is 60A, but it says 60a32v, will that do?

[valrene9600]

Hello!

 

What amp fuse would I need on a 12v system between my MPPT controller and the batteries with 500w of solar?

 

Upgrading from 250w, which currently has 30A fuse

 

:-)

Is the controller sufficient for the extra solar or are you upgrading the controller as well.

[Chewbacka]

Concerning your fuse question - Short answer is Yes, provided that the cable is suitable for 60A.

 

Long answer

A fuse is normally derated by 25% in other words you would use a 60A fuse to protect a circuit current of 45 Amps.

500W at 12V is 42Amps so your 60A fuse is fine but you MUST ensure the cable is safe at 60A. So 10mm2 is the minimum I would expect. For a 12v system to minimise power losses you would want a thicker cable, and that depends upon it's length, but from a safety viewpoint 10mm2 is ok.

 

 

The voltage rating is to ensure that any arc formed when the fuse blows will be extinguished, so the fuse voltage must be the same or higher than the circuit it is protecting, as you are 12V and the fuse is 32V, you will be ok.

 

Good point above - Is the controller ok for 500W of solar?

Edited August 19, 2015 by Chewbacka

[Lady_Trish]

Concerning your fuse question - Short answer is Yes, provided that the cable is suitable for 60A.

 

Long answer

A fuse is normally derated by 25% in other words you would use a 60A fuse to protect a circuit current of 45 Amps.

500W at 12V is 42Amps so your 60A fuse is fine but you MUST ensure the cable is safe at 60A. So 10mm2 is the minimum I would expect. For a 12v system to minimise power losses you would want a thicker cable, and that depends upon it's length, but from a safety viewpoint 10mm2 is ok.

 

 

The voltage rating is to ensure that any arc formed when the fuse blows will be extinguished, so the fuse voltage must be the same or higher than the circuit it is protecting, as you are 12V and the fuse is 32V, you will be ok.

 

Good point above - Is the controller ok for 500W of solar?

Yeah updating the controller from 20a to

40a. As for the cable, 10mm from controller to batteries, but 8mm between panals. This is what Bimble reccomends I think, is that ok?

Edited August 19, 2015 by Lady_Trish

[Chewbacka]

Short answer - if that is Bimble's recommendation it should be fine.

 

Long answer is that a heavier cable between the box and the batteries in theory would reduce your losses when at full power, but in the UK you will almost never see the full output, just not enough sun. So at the realistic charging levels you will get, then the cable will not make much difference. In case you are interested, the panels are measured at a sunshine level of 1000w per sq meter. This level of sunshine is the sun at mid day in Southern Europe, and with the panel pointing directly at it. Can't remember the last time we had a day like that.

 

Out of interest are you fitting them or getting someone to do it for you?

Edited August 19, 2015 by Chewbacka