If the battery side + of a controller is interrupted by a bat cutoff switch between the controller and the battery, are there any major problems with such a setup when turning the cutoff on and off during normal use.I ask, due to the fact that all controllers state to hook up battery connections first, then the panel connections. Maybe that is only to tell the controller what voltage it is looking at??

My solar controller is hooked directly to the battery posts. The disconnect does not affect it.

there can beit can damage the controller, depending on the controlleryou are not supposed to disconnect the batteries from the controller and leave the solar connected feeding the controllerthere is NO reason to disconnect the batteries from solar, except to change/service the batteries or cablesno reason or need to disconnect in storageIF you live in SNOW country and think your panels will covered to the point of NO output and want to disconnect the batteries and bring them inside for storagethen you should cover the panels, disconnect panels from controller, then disconnect batteriesmost people don't go thru all that trouble, they just leave everything connected so the solar can maintain the batteries

MrWizard wrote:there can beit can damage the controller, depending on the controlleryou are not supposed to disconnect the batteries from the controller and leave the solar connected feeding the controllerthere is NO reason to disconnect the batteries from solar, except to change/service the batteries or cablesno reason or need to disconnect in storageIF you live in SNOW country and think your panels will covered to the point of NO output and want to disconnect the batteries and bring them inside for storagethen you should cover the panels, disconnect panels from controller, then disconnect batteriesmost people don't go thru all that trouble, they just leave everything connected so the solar can maintain the batteriesX2

sch911 wrote:My solar controller is hooked directly to the battery posts. The disconnect does not affect it.Ditto.

TUCQUALA wrote:If the battery side + of a controller is interrupted by a bat cutoff switch between the controller and the battery, are there any major problems with such a setup when turning the cutoff on and off during normal use.Flipping the cutoff on and off is not what II would call a "normal use". Normal wiring would be controller to battery via its own breaker. Not directly to battery, and not via general cutoff switch. Same for loads - they should be connected to battery via "loads" breaker.Then you can disconnect either loads or controller or both, if needed. Disconnecting loads is what you do in storage, - this is better than battery disconnect because you stop battery drain but keep controller running, maintaining the battery. Or flip controller breaker if you absolutely have to - and then it should be the FIRST thing to do.In my trailer the only "battery disconnect" is a battery fuse, mounted on the battery Pos terminal. From there, Pos goes to Pos buss, and from there - to the aforesaid loads breaker and controller breaker. I bypassed the general trailer fuse under the frame - too darn inconvenient. Serious guys have a proper battery switch by Blue Sea, besides the battery fuse. I've been postponing this for years 'cause don't see what exactly it will give me.

How does solar play with a battery disconnect!!??

27 Replies

westend
Explorer
Mar 08, 2016
I have this manual Circuit breaker beteen module and controller. It makes an easy disconnect and also affords circuit protection.
2oldman
Explorer II
Mar 07, 2016
TUCQUALA wrote:
Further reading here kinda gives me the idea that a switch in the output of the solar panel is not a good idea either!! ????
I have a disconnect switch to cut off the panels. Much needed when doing any rewiring downstream, of which I've done a fair amount. I've not heard of any problems with that.

I switched them off, and back on. Appears the Outback has some pretty good 'padding' in there as the expected Voc voltage doesn't spike at all. It gradually rises.
time2roll
Nomad
Mar 07, 2016
TUCQUALA wrote:
Further reading here kinda gives me the idea that a switch in the output of the solar panel is not a good idea either!! ????
I have a 70 amp fuse in a holder that needs a screwdriver to remove.
Makes me stop and think vs. just flip a switch.
brulaz
Explorer
Mar 07, 2016
TUCQUALA wrote:

...

Further reading here kinda gives me the idea that a switch in the output of the solar panel is not a good idea either!! ????

I have a breaker between the panels and controller.
Is that what you mean?
It's recommended by my controller manufacturer.
TUCQUALA
Explorer
Mar 07, 2016
Thanks to all for your replies. Main reason I asked was that a wiring diag I saw for a trailer looked like the opt solar wires would be directly connected to the batteries. Looking closer (a fuzzy pdf!!) I can see that they are on the batt side of the cut off switch. So my question has been answered.

Further reading here kinda gives me the idea that a switch in the output of the solar panel is not a good idea either!! ????
MEXICOWANDERER
Explorer
Mar 07, 2016
There is ONE valid reason to disconnect panels from the batteries. Something is wrong and the circuit must be opened.

Hmmmm please bring Mountain to Mohammad...

Throw tarp, towels, sheets over the panels, removing them from sunlight.

Leave shading in place until the panels are ready to work again.
time2roll
Nomad
Mar 07, 2016
2oldman wrote:
If I have a catastrophe fuse on the battery +, why do I need one on the controller wire to the buss/battery?
Depends on the fuse and the wire size. And if the wire is in plain view and reasonably protected.
2oldman
Explorer II
Mar 07, 2016
Almot wrote:
If battery fuse blows - between the battery and buss - but the loads breaker remains open
You mean closed..as in 'not blown.'?

Kinda hard to see how a 300 amps cat fuse would blow but not a loads breaker. But yeah, I guess you don't want that 300 amps surging through your controller.

My wiring is pretty small so I could probably get by with a 60amp cat fuse.
Almot
Explorer III
Mar 07, 2016
pianotuna wrote:
My catastrophic failure fuses are 350 amps each. My wire from the battery buss to the controller is not capable of sustaining 350 amps, so I would fuse to the wire size between the controller and the battery bank. The rule is "always fuse to the wire size".

This is one reason, and here is another.

If battery fuse blows - between the battery and buss - but the loads breaker remains open (let's say for some brief time?) - then controller remains connected to loads via the same buss, while not connected to battery. No good.
pianotuna
Nomad III
Mar 07, 2016
My catastrophic failure fuses are 350 amps each. My wire from the battery buss to the controller is not capable of sustaining 350 amps, so I would fuse to the wire size between the controller and the battery bank. The rule is "always fuse to the wire size".

In addition, since I have twin battery banks and switches to select where the solar harvest is sent, I have fused to protect the lovely switches that have led's in the stem. This approach worked to my favor when a technician managed to wire my system for 24 volts. I lost one Castrophic failure fuse, the reverse polarity fuses in the converter, and one of the fuses protecting the switch on that "leg".

Perhaps some one might consider this a belt and suspenders approach, but it paid off *big time* for me.

2oldman wrote:
If I have a catastrophe fuse on the battery +, why do I need one on the controller wire to the buss/battery?