Disconnecting Batteries with Solar?

2oldman wrote:

stevenal wrote:
The fuse goes between the controller and battery to keep a short circuit in the controller, sourced by the battery, from starting that fire.

Yes, I should have said 'panels' in my reply. Most folks put a cat fuse on the battery to protect everything.

The wire and its fuse from the positive bus bar to the battery must be of sufficient ampacity for the total of all the amps going to the bus bar.

Individual positive wires and their fuses of various ampacities that go to the bus bar from different things (inverters, converters, solar controllers, jacks, slides, etc) need their individual fuses for their own wire sizes where their wires go back into the walls for different 12v things.

It is not good enough (AFAIK) to depend on the one fat wire's fuse at the battery to protect all those various wires of various AWGs that go to the bus. Any one of those wires could short by itself and needs its own fuse for that.

stevenal wrote:
The fuse goes between the controller and battery to keep a short circuit in the controller, sourced by the battery, from starting that fire.

Yes, I should have said 'panels' in my reply. Most folks put a cat fuse on the battery to protect everything.

2oldman wrote:
There's no compelling safety reason for fusing solar. It's not like they are batteries capable of runaway amperage starting fires.

The fuse goes between the controller and battery to keep a short circuit in the controller, sourced by the battery, from starting that fire.

Since it is hard to find solid info on which controllers will fry, it is best to assume the worst and have a way to disconnect the panels before you disconnect the batts from the controller.

Also, separate from that, many controllers are 12/24 and you need to connect to the batts first so the controller can see if it is 12 or 24 before you connect the panels.

For systems under 300 watts with a controller that won't fry without a battery connected there is no need to have either a fuse or circuit breaker between the panels and the controller.

If the controller may fry, then a simple DC switch is all that is needed.

There should be a fuse near to the battery bank for the run from the controller to the bank.

Lenny K wrote:
I did the same as Denver Transplant. It is not difficult to do and it makes any future work on your solar or batteries so easy and safe.
There is a solar installer in Quartzsite that I won't name..oops..Discount Solar that does not install any fuses or disconnects between the panels to the controller or from the controller to the batteries. They say it is not required. Makes you wonder about them doesn't it?

You're right in saying that you don't need fuses but you do need disconnects. I used the term safe in the sense that you won't possibly destroy your charge charger with all that current running around from your panels.

There's no compelling safety reason for fusing solar. It's not like they are batteries capable of runaway amperage starting fires.

I did the same as Denver Transplant. It is not difficult to do and it makes any future work on your solar or batteries so easy and safe.
There is a solar installer in Quartzsite that I won't name..oops..Discount Solar that does not install any fuses or disconnects between the panels to the controller or from the controller to the batteries. They say it is not required. Makes you wonder about them doesn't it?

Shutting off solar panels, as in covering, is step number one.

When I installed my solar panels and controller, I put circuit breakers in the + DC connections for both the panels and connection to the batteries. If you don't have fuses or circuit breakers in these circuits, you should consider adding them. They protect against accidental grounding and provide a convenient disconnect so you can work on components. Size based upon your system size. My controller is a nominal 30A controller so I used 40A breakers.

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