Disconnecting Batteries with Solar?

I think it depends on what MPPT CC you have. Mine states that you should disconnect the panels from the CC but no damage will occur if you don't disconnect. I've done both many times without damage. Don't especially recommend my unit, but it is a CNBOU MUSE 40 amp, 150 volt unit. Seems to work well with my 720 watts of series/parallel panels. I often see the full 40 amps charge current going into 3 series pairs of GC2 batteries. Sorry for the off topic ramble.

Hi,

You need to be able to disconnect the panels first, so the wire may not be a good plan.

The breaker between the controller and the battery bank should be extremely close to the battery bank end of the wire.

Spridle wrote:
for my small (3)100 watts solar panels i used this for disconnects breakers and fuses:

http://www.midnitesolar.com/productPhoto.php?product_ID=79&productCatName=BOX%20ENCLOSURES&productCat_ID=10&sortOrder=1&act=p

I used one 20 amp breaker to disconnect the solar panels to the charge controller and one 30 amp breaker to disconnect the charge controller feeding the battery's. use bushings in the holes of the box. I tied the breaker handles together with a piece of tie wire so they both disconnect at the same time.

http://www.midnitesolar.com/productPhoto.php?product_ID=184&productCatName=Breakers&productCat_ID=16&sortOrder=6&act=p

for my small (3)100 watts solar panels i used this for disconnects breakers and fuses:

http://www.midnitesolar.com/productPhoto.php?product_ID=79&productCatName=BOX%20ENCLOSURES&productCat_ID=10&sortOrder=1&act=p

I used one 20 amp breaker to disconnect the solar panels to the charge controller and one 30 amp breaker to disconnect the charge controller feeding the battery's. use bushings in the holes of the box. I tied the breaker handles together with a piece of tie wire so they both disconnect at the same time.

http://www.midnitesolar.com/productPhoto.php?product_ID=184&productCatName=Breakers&productCat_ID=16&sortOrder=6&act=p

Hi BFL13,

Thanks for finding that.

A quote from the article "For arrays with only one or two sub-arrays and sub-array cables adequately sized, fusing may only be required if local installation regulations or codes require them."

BFL13 wrote:
This explains all about the real requirements for solar array fusing. Scroll down to string and array protection.

http://www1.cooperbussmann.com/pdf/1b416a65-f5ac-4730-ab77-9e2faa147945.pdf

The fuse won't protect the RV from a lighting strike.

Traveler7 wrote:
ell, A lightning strike on the panel might give you a compelling reason...

Traveler7 wrote:

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

Well, A lightning strike on the panel might give you a compelling reason...

A fuse is not going to do much of anything in the event of a direct lightning strike. A spark energetic enough to jump a mile or so through the atmosphere is not going to be deterred by a quarter inch gap in a blown fuse.

Thank you all for your responses. I figured the panels had to be disconnected or something like that. Seems like I should cover the panels, disconnect panels from controller, disconnect batteries, Reverse the order when reconnecting.

I like the idea of a disconnect switch between the panels and controller.

This explains all about the real requirements for solar array fusing. Scroll down to string and array protection.

http://www1.cooperbussmann.com/pdf/1b416a65-f5ac-4730-ab77-9e2faa147945.pdf

Lightning strikes, panels bursting into flames. Yeah, I never thought of that. Thanks.

2oldman wrote:

brulaz wrote:

Windy Nation Web Site wrote:
.. if you have 4 panels each capable of up to 15 amps, then a short in one panel can draw all 60 amps towards that short-circuited panel. This will cause the wires leading to that panel to far exceed 30 amps causing that wire-pair to potentially catch fire.

I suppose that's possible, but it's difficult to imagine any 15 amp panel sustaining a 60a load for more time than the wire.

Right. It's likely to burst into flames before the interconnecting cables do. Oh, wait.