MPPT to Batteries Circuit breaker.

[HeywoodJ]

Not only is it not far-fetched, it is the basis of every single electrical code in existence. Over current protection (OCP) goes at the source end of any circuit, and is sized so that you don't damage the current carrying conductors. Despite what you might think, a battery is always a source end of a circuit, regardless of whether it is a charging circuit and you don't "think" it is a source. The charging device may also be a source and you may need OCP at both ends of the circuit, but in the OP's case solar panels and their attendant charge controllers are current-limited devices and are not considered a source (because they, by their nature, cannot deliver current in excess of their ratings - there is no source of additional electrons).

[Wotname]

^^
Very succinct explanation!

[Celestialsailor]

Originally Posted by Stu Jackson

jedi,


I guess thomm225 still hasn't gotten the Memo about his battery bank, however small it may be, is just a BIG BOMB waiting to go off and the only protection is that fuse he thinks is far fetched.


Heck, decades ago when somebody explained it to me that way, I hastened to listen and understand.


Anybody who still doesn't "get it" and thinks the fuse is only to protect the equipment downstream oughta get the Memo, too.

Oh, I can hardly wait for the usual rhetoric this is going to cause...

[thomm225]

Originally Posted by Stu Jackson

jedi,


I guess thomm225 still hasn't gotten the Memo about his battery bank, however small it may be, is just a BIG BOMB waiting to go off and the only protection is that fuse he thinks is far fetched.


Heck, decades ago when somebody explained it to me that way, I hastened to listen and understand.


Anybody who still doesn't "get it" and thinks the fuse is only to protect the equipment downstream oughta get the Memo, too.

Guess you missed my post above.

I’m ordering some in-line fuses and will install soon.

So far since 2011 I have been okay with 7 different batteries and 6 different controllers.

And 2 inverters..

I’m also thinking a solder run would blow in the controller or inverter before any major damage would occur (or component failure)

Or a component failure would cause an open doing the same thing..

I’ve smoked circuit cards with fat less current than what my batteries can deliver

[boatpoker]

I have these nifty inline breakers at both ends, between panels and MPPT controllers and between battery and controllers. Anything less is foolish and not ABYC compliant.

[s/v Jedi]

Originally Posted by boatpoker

I have these nifty inline breakers at both ends, between panels and MPPT controllers and between battery and controllers. Anything less is foolish and not ABYC compliant.

No, the controller end does not require fusing to be ABYC compliant (it is a limited current device, can never supply more than the panels can give and the wiring is sized to handle it).

It does reduce the reliability of the circuit by having two fuses in series, but safety wise it is completely fine

[noelex 77]

Circuit protection between the solar panels and the controller is not required in this case, but if you have three or more panels connected in parallel then a fuse or circuit breaker is required on the output of each solar panel.

This is in addition to a fuse between the controller and the battery (this is always required).

[boatpoker]

Originally Posted by noelex 77

Circuit protection between the solar panels and the controller is not required in this case, but if you have three or more panels connected in parallel then a fuse or circuit breaker is required on the output of each solar panel.

This is in addition to a fuse between the controller and the battery (this is always required).

Not in series, one at each power source with an appliance in between.

[s/v Jedi]

Originally Posted by noelex 77

Circuit protection between the solar panels and the controller is not required in this case, but if you have three or more panels connected in parallel then a fuse or circuit breaker is required on the output of each solar panel.

This is in addition to a fuse between the controller and the battery (this is always required).

Exactly

The reason for those fuses at each solar panel is to prevent fire in the solar panel itself, when it would develop a short and other panels start dumping energy into it.

[noelex 77]

Originally Posted by boatpoker

Not in series, one at each power source with an appliance in between.

If the panels are in series, circuit protection is not needed on the solar panel side.

I can see an exception in the rare case where the fuse value between the solar controller and the batteries is higher than the wire rating between the solar panel and the controller, but I have never seen this situation in practice on a sailboat and this would only be of value in a situation where multiple faults occurred.

Circuit protection between the batteries and solar controller is always needed.

However, the ability to switch off the solar panel input is useful. This can be a switch, but a circuit breaker is sometimes used, often because these can safely switch high DC voltages in a convenient form factor at a reasonable price.

I have used circuit breakers in this way in my own installation, although in this case it is one controller per panel. The circuit breakers between the solar panels and the solar controllers acts as a switch to turn off the solar panel input. See photo below:

[thomm225]

Originally Posted by noelex 77

However, the ability to switch off the solar panel input is useful. This can be a switch, but a circuit breaker is sometimes used......

Definitely.

Sometimes it appears both my panels are not working so I "switch one off" at a time by covering it with a heavy jacket or bed comforter folded.

Maybe when I install my battery/controller inline fuses I could think over a breaker setup for the panels.

I'll need more power if I start cruising for more than a week in the future so I may need to rethink my setup.

Smaller panels in photo are hooked to the batteries directly. The other two (65/50 watt) are going through 2 PWM controllers.

Now they go through my Smart Solar Blue Tooth Victron 75/15 which is mounted.

It's the first controller I have mounted as I was testing for the other years.

[Nicholson58]

I prefer two pole breakers on the solar connections. I also use them on each solar panel. This is a convenient disconnect for maintenance, reprogramming, electric storm isolation.

Three solar panels, one MPPT disconnect. DIN rail mount makes it easy. You could also use a fuse block like Blue Sea makes with fuses for each line.

[s/v Jedi]

Originally Posted by Nicholson58

I prefer two pole breakers on the solar connections. I also use them on each solar panel. This is a convenient disconnect for maintenance, reprogramming, electric storm isolation.

Three solar panels, one MPPT disconnect. DIN rail mount makes it easy. You could also use a fuse block like Blue Sea makes with fuses for each line.

Take care when using AC breakers for DC.

For solar panels, a 400VAC breaker as shown by N58 is good and even a 250V breaker will be okay, but a 120V breaker will not.

In most places you can easily buy DC breakers for DIN rails which is the best option

[patmvcr]

Originally Posted by noelex 77

Circuit protection between the solar panels and the controller is not required in this case, but if you have three or more panels connected in parallel then a fuse or circuit breaker is required on the output of each solar panel.

This is in addition to a fuse between the controller and the battery (this is always required).

Hmmm...

I didn't know this. I put 4 x 100 Renogy 100W Flexible Monocrystalline Solar Panels on top of my bimini when at anchor to keep my bank topped up. They are connected in parallel using a 4 way splitter to one cable to the controller (cable runs down the inside on my arch tubing). The panels are disconnected and stowed when underway and at the dock.

The setup was originally just 2 panels, so I guess my solar advisor didn't tell me a fuse was required at each panel. But now that I have 4 panels, I need one at each panel before the 4-way splitter?

[s/v Jedi]

Originally Posted by patmvcr

Hmmm...

I didn't know this. I put 4 x 100 Renogy 100W Flexible Monocrystalline Solar Panels on top of my bimini when at anchor to keep my bank topped up. They are connected in parallel using a 4 way splitter to one cable to the controller (cable runs down the inside on my arch tubing). The panels are disconnected and stowed when underway and at the dock.

The setup was originally just 2 panels, so I guess my solar advisor didn't tell me a fuse was required at each panel. But now that I have 4 panels, I need one at each panel before the 4-way splitter?

Yes, you actually have mc4 inline fuse holders compatible with your setup.