Turning solar panels off

[larryjc]

When I leave a boat for any length of time, (several months sometimes)  I like to turn everything off and isolate the batteries.  My last boat had 200w of solar panels and I fitted a cut off switch in the positive from the panels before the MPPT to turn them off  (they were wired direct to the batteries rather than through the battery main breaker).  It was also useful when mucking around with the electrics rather than having to chuck blankets over them.  The new boat has 500w of panels and I'm just about to change the PWM for a MPPT from Bimble.  I spoke to a solar electrician the other day and he said you should put a switch on the battery side of the controller and I note that the Bimble wiring diagrams also have a DC breaker on the battery side.

This seems odd to me as when you wire the panels up its made very clear that you must connect the battery wires to the controller first and the panels afterwards.  Surely putting a switch in the battery side means that you will be effectively doing the opposite every time you make the switch??  Any thoughts would be gratefully received.

[peterboat]

According to my mppt controller {midnite] it will fry the controller! Why disconnect the panels? your batteries are best left fully charged and solar doing its stuff it wont over charge them

[rusty69]

I turn our panels off with a switch (only when fully charged) as the controller has a fan in it which becomes annoying when it starts up at 5am in the summer months. It is between the panel and controller.

Edited March 5, 2017 by rusty69

[larryjc]

Why should it fry the controller?  It didn't do that to my last one (Victron).  When connecting up for the first time, the battery terminals are connected first with no leads from the panels until they are connected afterwards, which is exactly the same as switching them off with the switch on the solar panel side.

Again from my last boat,  when I left the panels on and got back, the batteries were absolutely maxed - not a bad thing but when I started the engine the alternator started overvolting because their internal resistance was so high.  When I switched everything off they still have a 12.8 volts open circuit on them after two months.  Also live electrics of any sort on an empty boat never seems a good idea to me.  And on top these points there are times when I want to fiddle with the boats electrics and need to turn everything off, the only alternative with panels is to chuck blankets over them and my wife gets snotty about that for some unknown reason.

I'm happy to fit a switch wherever it should be just can't follow the logic of fitting it past the controller if the initial installation instructions are so adamant about the sequence you must follow.

[rusty69]

38 minutes ago, larryjc said:

  I spoke to a solar electrician the other day and he said you should put a switch on the battery side of the controller and I note that the Bimble wiring diagrams also have a DC breaker on the battery side.

 

I would think that is correct.

[larryjc]

Actually just looked at the manual for the Tracer controller and it shows the breaker on the Solar panel side - I am now horribly confused and have emailed Bimble.

[mross]

My domestic system has a DC breaker before the inverter an AC breaker after it and another AC breaker next to the consumer unit.  But no instructions on which order I should turn them off in.

[Jess--]

If you want to add a switch (to shut down solar) it should be between the panels and the controller.

anything between the batteries and controller is there for protection or for maintenance isolation (cut the power in case of a fault or while the system is being worked on).

on mine I have no switches and the solar system bypasses the battery isolator but has it's own fuse for protection, therefore the solar system is never disconnected from the bank of leisure batteries.

on Wednesday of this week when I visited the boat for the 1st time since november the leisure batts were at 13.9v (with solar connected) and the starter batt was at 12.2v, starting then engine lifted both to 14.4v before settling back down to 13.9v

 

1 minute ago, mross said:

My domestic system has a DC breaker before the inverter an AC breaker after it and another AC breaker next to the consumer unit.  But no instructions on which order I should turn them off in.

logically you start from the source of power and work back from there... dc breaker then either ac breaker (since it sounds like they are in series)

[larryjc]

1 minute ago, Jess-- said:

 

anything between the batteries and controller is there for protection or for maintenance isolation (cut the power in case of a fault or while the system is being worked on).

 

Yup - but thats my problem - I may well want to 'cut the power while the system is being worked on'  and if I use a switch between battery and controller, then logically when I switch the system back on it will be reconnecting the controller in the wrong sequence - ie the panels are already connected and the batteries are now being reconnected second.

[Tony Brooks]

15 minutes ago, rusty69 said:

I would think that is correct.

Above answer to Larry C -   I spoke to a solar electrician the other day and he said you should put a switch on the battery side of the controller and I note that the Bimble wiring diagrams also have a DC breaker on the battery side.

 

I understand  many solar controllers are auto-sensing dual 12/24 units and if you connect the batteries AFTER the panels the controller may well set itself for 24 volt operation (and visa versa for a 24 volt system). I thought the golden rule is connect battery first then panel so a switch on the battery side may well cause all sorts of problems.

 

I also think the OP's idea is needless unless he has a shorted cell. Why invite sulphation caused by self discharge when you have the means to avoid it. See Jess's post.

[larryjc]

2 minutes ago, Tony Brooks said:

I also think the OP's idea is needless unless he has a shorted cell. Why invite sulphation caused by self discharge when you have the means to avoid it. See Jess's post.

Maybe - part of my idea, as the old boat had AGMs and the new one will have Trojans BUT I will still want to turn the panels off at some time for other reasons as I have explained.

[rusty69]

14 minutes ago, Tony Brooks said:

Above answer to Larry C -   I spoke to a solar electrician the other day and he said you should put a switch on the battery side of the controller and I note that the Bimble wiring diagrams also have a DC breaker on the battery side.

 

I understand  many solar controllers are auto-sensing dual 12/24 units and if you connect the batteries AFTER the panels the controller may well set itself for 24 volt operation (and visa versa for a 24 volt system). I thought the golden rule is connect battery first then panel so a switch on the battery side may well cause all sorts of problems.

 

I also think the OP's idea is needless unless he has a shorted cell. Why invite sulphation caused by self discharge when you have the means to avoid it. See Jess's post.

Sorry, it probably wasn't clear. I think the DC circuit breaker(or fuse) is required, but not the switch on the battery side.

The switch between panel and controller , in my case is very useful, as it allows me to turn one string of panels off, leaving a remaining panel to charge the battery without having to listen to a noisy fan at 5am.

 

Note to self to invest in silent controller .

Edited March 5, 2017 by rusty69

[Jess--]

9 minutes ago, larryjc said:

Maybe - part of my idea, as the old boat had AGMs and the new one will have Trojans BUT I will still want to turn the panels off at some time for other reasons as I have explained.

then put a switch between the panels and the controller and a fuse between the controller and batteries.

if you want to shut it down turn the switch off
if you want to work on it then turn the switch off and pull the fuse

just remember no matter how many switches you have the wiring from the panels will ALWAYS be live if the panels have light falling on them, depending on how they are wired this could be over 70v (2 panels in series @35v each open circuit)

Edited March 5, 2017 by Jess--

[larryjc]

1 minute ago, Jess-- said:

then put a switch between the panels and the controller and a fuse between the controller and batteries.

if you want to shut it down turn the switch off
if you want to work on it then turn the switch off and pull the fuse

 

Aaaaargh - this goes right back to my original question - it appears that some people are saying that putting a switch on the panel side is incorrect and I'm trying to find the right answer.

[Jess--]

1 minute ago, larryjc said:

Aaaaargh - this goes right back to my original question - it appears that some people are saying that putting a switch on the panel side is incorrect and I'm trying to find the right answer.

the switch is there for general use, i.e. "I don't want to charge my batteries today"

the fuse is there for protection or maintenance, i.e. "My controller is on fire and I need to replace it"

[rusty69]

1 minute ago, larryjc said:

Aaaaargh - this goes right back to my original question - it appears that some people are saying that putting a switch on the panel side is incorrect and I'm trying to find the right answer.

Perhaps it depends on your controller. As peterboat above said, for his midnite one  its a no.

[WotEver]

This has gone back and fro and I think OP might be in danger of getting confused. Hopefully this will help. 

The very least that a solar system requires is a fuse/breaker close to the batteries to protect the 12V cable from the controller. This MUST be fitted for your safety. Pulling the fuse or switching off the breaker will function as an isolator (but see below).

If you wish to fit a switch between panels and controller then feel free to do so but do ensure that it's DC rated for both the voltage and current that it will be carrying. 

If you wish to fit a switch between panel and batteries then you should only operate it if the panels are disconnected either by being unplugged/switched off (if you've fitted a switch), or if they are covered with a blanket. 

Edited March 5, 2017 by WotEver
Tidy it up a bit

[rusty69]

32 minutes ago, WotEver said:

 

If you wish to fit a switch between panel and batteries then you should only operate it if the panels are disconnected either by being unplugged/switched off (if you've fitted a switch), or if they are covered with a blanket. 

Or it is  dark.

Edited March 5, 2017 by rusty69

[larryjc]

I was confused and I still am because no one here seems to want to  respond to my actual question.  I know about the need for a fuse - I didn't ask about that. At the risk of endlessly repeating myself - there is conflicting advice as to where it is safe to fit a switch for the purpose of isolating the panels from the boat (for whatever reason).  Some advice I've been given is that is MUST be after the controller - which seems to conflict with the initial wiring sequence requirements.  Some say it can be before the controller.  Thanks for all the input, hoepfully Bimble will come backe to me and I'll post any response here.

[mross]

But your question has been answered!  Click on blue text below.

 

[WotEver]

27 minutes ago, rusty69 said:

Or it is  dark.

Indeed

4 minutes ago, mross said:

But your question has been answered!  Click on blue text below.

 

Thank you, I thought it was me for a moment...

14 minutes ago, larryjc said:

no one here seems to want to  respond to my actual question.

I did. In detail. 

[Tony Brooks]

1 hour ago, larryjc said:

Aaaaargh - this goes right back to my original question - it appears that some people are saying that putting a switch on the panel side is incorrect and I'm trying to find the right answer.

 

OK - then put it wherever you like but do not come back on us if you damage something.

I believe I gave you the reason why putting a switch between panel and controller is a bad idea and my controller instructions make that perfectly clear. Personally I would rather trust the instructions that came properly translated from a German company that those in pigeon english that come with some far eastern products. I would also rather trust the written instructions for a particular controller than a comment from an unnamed "solar electrician" that I take to mean solar installer.

[larryjc]

Alright - I'm not trying to be anal.  It seems the concensus here is that my desire to fit a switch between panel and controller is fine. However, Tony you say in one post 'so a switch on the battery side may well cause all sorts of problems,' and then just now you said 'I gave you the reason why putting a switch between panel and controller is a bad idea.'   Maybe you can see why I'm slightly confused.

I would never 'come back' to anyone on this forum after taking advice.

 

Edited March 5, 2017 by larryjc

[mross]

Fit a circuit breaker before and after the controller.  Switch off panels then battery; switch on battery before panels. BUT READ THE MANUAL for your MPPT first.

[WotEver]

31 minutes ago, larryjc said:

Alright - I'm not trying to be anal.  It seems the concensus here is that my desire to fit a switch between panel and controller is fine. However, Tony you say in one post 'so a switch on the battery side may well cause all sorts of problems,' and then just now you said 'I gave you the reason why putting a switch between panel and controller is a bad idea.'   Maybe you can see why I'm slightly confused.

I would never 'come back' to anyone on this forum after taking advice.

 

That was a typo by Tony B. Please re-read what I wrote.

Tony