Break Pos or Neg on Solar Panel wire to controller

[ramblinrod]

Wow. Lots of posts to what I thought was a simple question, didn't mean to start a war with this. I didn't want to 'throw a blanket over the panels' they are 6' off the transom and I need to work down below, kind of pita to go up the stairs, out the salon, thru the cockpit to cover or uncover when a simple switch where the controllers and battery and gauges and wiring would make life easier..

Clearly any break in the circuit works. I have seen homeowners put an electrical switch on the white common wire and it will of course turn off the light. However, it is conventional to break the hot wire. So I can turn off the neg, and the circuit is broken, just didn't know if any issues of controller input taking in + with neg broken. Didn't think there would be, but just checking

Note there is an accidental quotation coding error in posts 67, 68, 70, 71,72, and 75, which makes it appear that quotations are by other than who actually posted.

[chala]

Originally Posted by travellerw

I wondered why someone would actually disconnect thier solar from the controller except to service it (in that case you could even used blankets to kill the output).

Wonder no more. It all depends on what type off regulator someone own and how that regulator is used.

If the regulator is of the type that automatically detects the battery voltage, 12, 24 etc then the regulator may require that the solar panel be connected last.

If the regulator is used to feed individual batteries, let say for charging or equalizing each battery in turn, then a switch on the feed from the solar panel that is reliable would be convenient.

By the way due to this feature, "1b) PV voltage must exceed Vbat + 5V for the controller to start", a Victron regulator may not be suitable.

[Pelagic]

Originally Posted by PaulinOz

A double pole DC rated circuit breaker like this solves all your questions and concerns.

It is also the way to have a switch and fuse capability on both Positive and Negative led from the solar panel to the controller.

DC Mini Circuit Breaker | Langir Electric

This is exactly what was recommended by a Solar installer.

Much neater /terminates both pos + neg cables/ and isolates DC Buss Bars from any residual currents when working on your DC systems

[john61ct]

Originally Posted by PaulinOz

A double pole DC rated circuit breaker like this
...
DC Mini Circuit Breaker | Langir Electric

Is this supplier trusted, those breakers will safely carry their rated capacities? If so I may use for my 60A LFP 12V 4-blocks, 1C that's about the fastest I'd want the flow in or out. Saves space, buying switches separately as well.

Just worried by the low prices. . .

Double thermostat looks useful for my LFP bank as well.

Any US sources to reduce shipping overheads? eBay only carries their switches.

[Bleemus]

Amazon has those switches as well.

[john61ct]

Links please, don't see them

https://www.amazon.com/gp/aw/s/ref=is_s?k=langir+switch

maybe you mean another brand you've used and trust, or recommended by a good authority?

I don't rely on Amazon reviews for this sort of gear.

That said I've also asked for more confirmation on Langir, talking heavy amps for this DIFFERENT use case, safety first, not just isolating a low-amp self-limiting source like panels.

[Bleemus]

https://www.amazon.com/LANGIR-500vdc.../dp/B012MWNSY8

[john61ct]

Of course, breaker not switch! Thanks

[OrangeCrush]

Apologies for the thread drift but I have a quick related question:

I bought a 25amp breaker and installed it between the controllers and battery for my two 100w panels. Then I realized I had the space and I added a third panel/controller. If all my panels are putting out their maximum power at the same time and my battery voltage is low, then the current could be exactly 25amps (300 watts divided by 12.0 = 25). Then again they are cheap panels and they might not reach their max power rating, plus my battery will hopefully not get that low very often.

So how much buffer room is recommended when sizing the breaker, and how likely am I to trip the 25amp breaker while charging? I'll buy a new one if necessary but I'm thinking it might be just enough.

[john61ct]

Actually you're really protecting the wires etc from fire, danger being the bank shorting or something.

From the bank, worst case you trip a breaker.

It would need to be a very cold and bright day, and since there's losses involved in wiring and the controller, very unlikely.

[Wotname]

Originally Posted by OrangeCrush

Apologies for the thread drift but I have a quick related question:

I bought a 25amp breaker and installed it between the controllers and battery for my two 100w panels. Then I realized I had the space and I added a third panel/controller. If all my panels are putting out their maximum power at the same time and my battery voltage is low, then the current could be exactly 25amps (300 watts divided by 12.0 = 25). Then again they are cheap panels and they might not reach their max power rating, plus my battery will hopefully not get that low very often.

So how much buffer room is recommended when sizing the breaker, and how likely am I to trip the 25amp breaker while charging? I'll buy a new one if necessary but I'm thinking it might be just enough.

The real answer is to know the "time/current curve" (or trip curve) of the breaker you are using but the short answer is that a 25 amp breaker will carry 25 amps for a long time - possibly hours.

[Bleemus]

Originally Posted by OrangeCrush

Apologies for the thread drift but I have a quick related question:

I bought a 25amp breaker and installed it between the controllers and battery for my two 100w panels. Then I realized I had the space and I added a third panel/controller. If all my panels are putting out their maximum power at the same time and my battery voltage is low, then the current could be exactly 25amps (300 watts divided by 12.0 = 25). Then again they are cheap panels and they might not reach their max power rating, plus my battery will hopefully not get that low very often.

So how much buffer room is recommended when sizing the breaker, and how likely am I to trip the 25amp breaker while charging? I'll buy a new one if necessary but I'm thinking it might be just enough.

Cheap panels and voltage drop on wire length will both keep you from hitting 25amps I would imagine.

[mako]

Originally Posted by Hilbert

From my controller's manual: "A clean connection to the battery (such as is provided by a disconnect or breaker) is required on power-up. Intermittent or noisy connections can cause the controller to initialize improperly"

I used a Blue Sea's battery switch for the battery disconnect (positive wire).

For a solar panel disconnect, I used an SPST toggle switch (positive wire). I was able to get away with this because my requirements were only for 33.2 VDC/ 7.3 amps, which was at the high end of the toggle switch rating. If it ever becomes a problem, I'll either replace it with another toggle or swap it out with something more robust.

Battery Panel:

Ideally would it be better to use a double pole switch that breaks contact for both positive and negative wires? Or is there some cautionary or safety reason to leave the negative/ground wire connected?

[ramblinrod]

Originally Posted by OrangeCrush

Apologies for the thread drift but I have a quick related question:

I bought a 25amp breaker and installed it between the controllers and battery for my two 100w panels. Then I realized I had the space and I added a third panel/controller. If all my panels are putting out their maximum power at the same time and my battery voltage is low, then the current could be exactly 25amps (300 watts divided by 12.0 = 25). Then again they are cheap panels and they might not reach their max power rating, plus my battery will hopefully not get that low very often.

So how much buffer room is recommended when sizing the breaker, and how likely am I to trip the 25amp breaker while charging? I'll buy a new one if necessary but I'm thinking it might be just enough.

The correct question is, what is the max safe current carrying capacity of the wires between battery and controller. Select the breaker at or below that level. If the breaker is too light for the maximum output of the controller, that means your cables are too light.

(Secondary to this, check the controller I.M., it may have built in charge current limiting ability to protect the controller from overheating.)

[camel2012]

Originally Posted by Wotname

The real answer is to know the "time/current curve" (or trip curve) of the breaker you are using but the short answer is that a 25 amp breaker will carry 25 amps for a long time - possibly hours.

Unless defective, hydraulic magnetic breakers (typical for marine) should pass 100% of rated current forever...they typically are tested to trip at either 110 - 120 % but would take a few hours ... everything in life has tolerances , especially circuit protection devices, so depending on the manufacturer and how they calibrated the breakers you are using you may see a nuisance trip.