25mm2 cable

[blackrose]

Ok so breakers are safety devices and can't be used as isolators? Are there any isolators that can be fitted? 

 

I don't really understand why boat batteries can be isolated even under load, but panels have to be covered?

[GUMPY]

9 minutes ago, blackrose said:

Ok so breakers are safety devices and can't be used as isolators? Are there any isolators that can be fitted? 

 

I don't really understand why boat batteries can be isolated even under load, but panels have to be covered?

Because the switches are designed to work under load the MC4 are not. 

[jonathanA]

Me neither. I don't cover up the 12 panels on the house roof but they do have a dc isolator.  And I wouldn't do any work on that system without isolating the panels and / or the mains.  

 

I don't see why you can't use suitably rated (for DC) breakers as isolators that's what they are for.  

 

Or one of these

 

https://www.ebay.co.uk/itm/134214731942?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=wc8xihkds6u&sssrc=2349624&ssuid=7VsQHjvdQA-&var=&widget_ver=artemis&media=COPY

Edited September 12, 2022 by jonathanA
Add linky

[blackrose]

Thanks. I wasn't suggesting using the MC4 interconnects to isolate the panels, I'd use suitable isolators just as I do with my batteries.

 

Perhaps it's just me but covering panels just doesn't seem the most reliable or even sensible method of removing the load and isolating them. Suppose you cover them for example, and then go down into the engine hole to work on the battery interconnects or fuses and outside unbeknownst to you the wind blows your panel covers off... You could tie the covers on but it just seems like a bit of a hassle every time you want to do something. 

 

To be honest I'm a bit surprised that there isn't an option on the controller to isolate the panels. Or is there? Epever 60amp. I can't see anything in the manual.

Edited September 12, 2022 by blackrose

[GUMPY]

With suitably rated isolators there is no need to cover the panels. Just remember to always reconnect the panels after the batteries.

[BEngo]

Covering panels means you can immediately disconnect them at the nearest convenient MC4 connector.  After that it won't matter if the covers come off. 

You should put the covers back before reconnecting the panels.

 

N

[ditchcrawler]

3 hours ago, blackrose said:

Why do the panels have to be covered when you're working on the system? Why can't they just be disconnected/isolated? Does the voltage have to go somewhere if they're left uncovered?

But the cable you are disconnecting will have 40+ volts on it. OK if its a MC4 as stated earlier they are shielded so you cant touch the conductors. Not so good it its terminals or other plug and socket.

[peterboat]

8 hours ago, Alan de Enfield said:

 

My panels are 120v EACH, if I wired them in series I'd soon be up in 'dangerous DC voltage' country. 120v is bad enough.

I am at 198 volts ish on my panels 3 strings of 5 x 330 watts a panel. Great for the immersion heater though. In reality I can't do parallel and I do need over 80 volts for the drive batteries. 

[peterboat]

1 hour ago, blackrose said:

Thanks. I wasn't suggesting using the MC4 interconnects to isolate the panels, I'd use suitable isolators just as I do with my batteries.

 

Perhaps it's just me but covering panels just doesn't seem the most reliable or even sensible method of removing the load and isolating them. Suppose you cover them for example, and then go down into the engine hole to work on the battery interconnects or fuses and outside unbeknownst to you the wind blows your panel covers off... You could tie the covers on but it just seems like a bit of a hassle every time you want to do something. 

 

To be honest I'm a bit surprised that there isn't an option on the controller to isolate the panels. Or is there? Epever 60amp. I can't see anything in the manual.

I have high voltage CD MCBs on my strings of panels to isolate them, it's what midnite solar recommends. Also MCBs into the batteries easier to turn off again, trouble is DC MCBs are expensive 

[jonathanA]

1 hour ago, blackrose said:

Thanks. I wasn't suggesting using the MC4 interconnects to isolate the panels, I'd use suitable isolators just as I do with my batteries.

 

Perhaps it's just me but covering panels just doesn't seem the most reliable or even sensible method of removing the load and isolating them. Suppose you cover them for example, and then go down into the engine hole to work on the battery interconnects or fuses and outside unbeknownst to you the wind blows your panel covers off... You could tie the covers on but it just seems like a bit of a hassle every time you want to do something. 

 

To be honest I'm a bit surprised that there isn't an option on the controller to isolate the panels. Or is there? Epever 60amp. I can't see anything in the manual.

There is on the victron blue solar controllers. Which is what I use, ( but has to be done via the app. )

 

And I included a link for a suitable isolator off fleabay sure cheaper versions are around.  These seem fine for house panels which are far larger than even Peterboats setup

[ditchcrawler]

8 minutes ago, jonathanA said:

 

 

And I included a link for a suitable isolator off fleabay sure cheaper versions are around.  These seem fine for house panels which are far larger than even Peterboats setup

But even that has to be connected in the first place

[peterboat]

21 minutes ago, jonathanA said:

There is on the victron blue solar controllers. Which is what I use, ( but has to be done via the app. )

 

And I included a link for a suitable isolator off fleabay sure cheaper versions are around.  These seem fine for house panels which are far larger than even Peterboats setup

I am at about 5kw so house size, but yes there are even bigger household arrays 

[blackrose]

45 minutes ago, ditchcrawler said:

But the cable you are disconnecting will have 40+ volts on it. OK if its a MC4 as stated earlier they are shielded so you cant touch the conductors. Not so good it its terminals or other plug and socket.

 

But why even disconnect the MC4 connectors? Why not just flip a suitably sized & specd isolator?

[blackrose]

32 minutes ago, jonathanA said:

And I included a link for a suitable isolator off fleabay sure cheaper versions are around.  These seem fine for house panels which are far larger than even Peterboats setup

 

Thanks, sorry I missed that link earlier. Is that suitable for a two panel setup in series? 

Edited September 12, 2022 by blackrose

[Richard10002]

8 minutes ago, blackrose said:

 

But why even disconnect the MC4 connectors? Why not just flip a suitably sized & specd isolator?

I use a breaker between panels and controller, which also acts as a switch. In fact I have a few similar breakers enabling me to cut the power to/from a couple of other things.

 

There is no way I would be pissing about covering panels or disconnecting MC4 connectors, when I can flick a handy switch.

[GUMPY]

5 minutes ago, Richard10002 said:

I use a breaker between panels and controller, which also acts as a switch. In fact I have a few similar breakers enabling me to cut the power to/from a couple of other things.

 

There is no way I would be pissing about covering panels or disconnecting MC4 connectors, when I can flick a handy switch.

The only time I have disconnected my panels was when the boat was repainted. Hardly worth putting an isolator on for that

.

And i disconnected after dark so no covering needed 

[blackrose]

 

2 hours ago, Loddon said:

With suitably rated isolators there is no need to cover the panels. Just remember to always reconnect the panels after the batteries.

 

These high DC voltages are new to me. With a mains battery charger switched on you don't need to worry too much, but I switch mine off when topping up the batteries, but that's mainly to avoid any bubbling acid emissions when I flip open the cell lids.

 

I think I'll put a notice on the battery box to remind me to isolate the panels. Are there any capacitors, etc in the controller that could give me a belt even with the panels isolated?

 

Edit: sorry I guess by the time the current has left the controller the voltage has been regulated, so it's the same as a battery charger?

Edited September 12, 2022 by blackrose

[ditchcrawler]

31 minutes ago, blackrose said:

 

But why even disconnect the MC4 connectors? Why not just flip a suitably sized & specd isolator?

How do you connect the isolator in the first place? Cover the panels.

Its a mater of specifying which bit of the system you plan to work on, hopefully none of it once connected.

13 minutes ago, blackrose said:

 

 

These high DC voltages are new to me. With a mains battery charger switched on you don't need to worry too much, but I switch mine off when topping up the batteries, but that's mainly to avoid any bubbling acid emissions when I flip open the cell lids.

 

I think I'll put a notice on the battery box to remind me to isolate the panels. Are there any capacitors, etc in the controller that could give me a belt even with the panels isolated?

 

Edit: sorry I guess by the time the current has left the controller the voltage has been regulated, so it's the same as a battery charger?

I would suggest once your solar system is up and running you leave well alone and don't go round turning things on and off, that seems to be when problems start. Also power it up in the correct order.

[blackrose]

21 minutes ago, ditchcrawler said:

How do you connect the isolator in the first place? Cover the panels.

Its a mater of specifying which bit of the system you plan to work on, hopefully none of it once connected.

 

I would suggest once your solar system is up and running you leave well alone and don't go round turning things on and off, that seems to be when problems start. Also power it up in the correct order.

 

Yes I understand the panels need to be covered during installation, I was talking about after that.

[cuthound]

When I.was working I always used to specify DC MCCB's (Moulded Case Circuit Breakers) to isolate DC sources. Unlike MCB's (Miniature Circuit Breakers), they are rated for frequent isolation.

 

Something like the 63A version of this.

 

https://www.mitsubishielectric.com/fa/products/lvd/lvcb/items/dcmccb/index.html

Edited September 13, 2022 by cuthound
Clarification

[blackrose]

On 12/09/2022 at 11:06, Jen-in-Wellies said:

You only have two panels. If you place them close together and remember not to moor in shade, then there are no advantages to parallel. 

 

I'm pretty sure I'll connect them in series. The only thing I still don't understand is that if you connect in series you double the voltage, if you connect in parallel you double the amps.

 

So if you connect in parallel and have double the amps going into the controller don't you get more amps coming out of the controller to the batteries? Or doesn't it work like that?

[Jen-in-Wellies]

4 minutes ago, blackrose said:

 

I'm pretty sure I'll connect them in series. The only thing I still don't understand is that if you connect in series you double the voltage, if you connect in parallel you double the amps.

 

So if you connect in parallel and have double the amps going into the controller don't you get more amps coming out of the controller to the batteries? Or doesn't it work like that?

Power (Watts) = Volts x Amps. For the same power out of the panels, if the volts goes down the amps go up and visa versa. 

Amongst other things, the MPPT controller is converting from a high voltage from the panels, either in series, or in parallel, to something close to 12V for the batteries. The current in to the batteries goes up correspondingly, but the power remains the same.*

 

*minus some conversion losses of course.

Edited September 13, 2022 by Jen-in-Wellies

[blackrose]

Ok I see. Thanks.

[Alan de Enfield]

30 minutes ago, blackrose said:

Ok I see. Thanks.

 

 

If you look at my 'monitor' you'll see that the panel is outputting 103.1 volts and 0.8 amps.

 

 

 

The MPPT controller takes this input, shakes it around a bit, checks the state of charge of the battery, decides the battery will take 14.7v and converts the 103 volts to 14.7 volts which results in the 0.8 amps being bumped up to 5.9 amps.

 

 

 

 

The other pictures shows the  panel output at 96.9 volts / 1.6 amps and the MPPT juggles it about and puts out 14.6 volts / 10.8 amps

 

 

 

 

 

 

 

 

Edited September 13, 2022 by Alan de Enfield

[blackrose]

This is a schematic of my proposed installation. Does it look ok? Any glaring errors? I'm using 6mm2 cable from panels to controller over a 6m (one way) distance and 25mm2 cable from controller to batteries (2m one way). Should the 60amp megafuse be close to the batteries or controller?

 

Edited September 16, 2022 by blackrose