Circuit Breaker For Solar Charge Controller To Battery Q's

tick

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On wills site it says the recommended 40 amp controller for 24v 2000W system requires 50 amp breaker, ... Shown above



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So if Using a victron 50 amp controller, the 60 amp breaker is correct?


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And a separate Question when sizing for Fuse --- When using the Recommended 2000 W sine wave inverter1595531725898.png
I should go with the 150 amp fuze and wire ?
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24 volt system, 960 watts solar (3 320watt sunpower) . 2000 W sine wave inverter. victron 100/50


Any reply's Welcomed and appreciated
 

Dzl

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[On wills site it says the recommended 40 amp controller for 24v 2000W system requires 50 amp breaker,

So if Using a victron 50 amp controller, the 60 amp breaker is correct?

Sounds good. Make sure the wire is sized to handle more than 60A also

And a separate Question when sizing for Fuse --- When using the Recommended 2000 W sine wave inverter
I should go with the 150 amp fuze and wire ?

This is the Giandel 2000W inverter, and a 24V system? If so, I think a 150A fuse sounds about right, and the wire needs to be sized to be able to handle more than the fuse, and account for voltage drop which depends on length of the wire.
 

jesfl

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I am a real novice, and I am confused (again).

I have an EPEVER Tracer 4215BN 40 Amp Solar Charge Controller installed in my 5-month old DIY solar system. It is a 12-volt system. There are eight (8) 100W panels wired series (2 strings of 4 panels each string) to parallel and then to the controller. By my calculations from the solar panel specs, that means I could be getting a maximum (peak performance) of 79.32 Volts and 12.52 Amps into the controller on a perfect mid-summer day with the sun directly overhead my flat-mounted RV rooftop panels.

Two weeks ago, I installed a 50 Amp breaker in the controller positive output cable from the solar controller to the batteries . . . just because I had an extra 50 Amp breaker. I reasoned it would do no harm and might somehow safeguard against a catastrophic problem? At that time, I had no idea a breaker might even be needed per this discussion for a 24-volt system. Even so, from the discussion here and elsewhere, I assume a breaker is not really needed in a 12-volt system?

When I installed the breaker. it just seemed logical, even though I thought I understood the maximum output from the controller was 40 Amps?

Well, twice in the past two weeks the circuit breaker has flipped off shutting down the solar controller completely. It happened in late afternoon past the peak sun position on beautiful sunny southern Arizona desert days.

-- Why is the 40 Amp controller causing the 50 Amp breaker to flip off?
-- Is my understanding about the 4215BN supposed maximum output of 40 Amps correct?
-- Is this a problem with the Tracer 4215BN solar controller?
-- Is it somehow a problem with my wiring?
-- How much trouble am I in here?
-- Should I just remove the breaker?

I am hoping to understand this problem. Any suggestions are welcomed.

Thank you.
 

mikefitz

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If its a low cost breaker then problems are to be expected, they rarely operate to specification. Use an alternative quality breaker or fuse. As you suggest the maximum output from the controller is 40 amps.

The fuse or breaker is intended to protect against fault conditions that may overload cables and wiring within electrical items. In your system you have a solar controller connected with cable to a battery, any fault in the solar controller or in the cable run could result overheating, perhaps leading to smoke and fire. Fitting a suitable fuse or breaker at the power source end of the cable, in this case the battery, would offer protection.

Many of the videos and diagrams show the breakers and fuses in positions that are not ideal and would not offer protection.

Any system with a high capacity battery of any voltage is capable of melting cables and setting fire to nearby materials.

Mike
 

jesfl

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May 17, 2020
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Mike,

WOW! Thanks so, so much for taking the time to help me. Your information is immensely valuable to this novice.

I read it is either: (1) a (cheap) faulty breaker, or (2) something in my system causing a surge of power in the cable from the solar charge controller to the batteries.

The breaker is possibly the problem, as it is a who-knows-what brand, probably Chinese, from Amazon.com. I didn't know any better. I looked again online and found a Blue Sea Systems 50 amp breaker, and since I used that brand a lot in past years on various boats, I am under the impression it is a higher quality product (and more expensive, of course). Is there a different, higher quality breaker I should consider?

The breaker has not flipped off again since the first two incidents (now for about 2 weeks, I'm guessing). So, possibly it was an anomaly?

I don't know whether it matters, but recently I read an article that basically argued "a larger sized wire/cable is ALWAYS better, and does no harm," So, I actually installed the breaker because I was changing the output-side +/- wire/cable from the solar charge controller to the batteries from 10 AWG to 6 AWG, because I had extra 6 AWG wire and figured it would do no harm. (The input wire from my solar panels is 10 AWH, per the panel's specs.) I assume this is not a factor in the breaker flipping.

FYI, my solar controller and my inverter are wired into my system via a busbar using 2/0 AWG wire (3 12-volt LiFePO4 150 Ah batteries). Per one spec I read, I put a 100 amp fuse on the battery-end of the short cable from the busbar to the batteries. Unless that's the wrong size fuse, I'm guessing I kinda' got that correct, per your suggestions.

I've been in the process of installing (plus rewiring, repairs, replacements) my DIY solar system for nearly 6 months. Every week there seems to be another, new issue of some sort. Or, I learn of something I could do better, such as rewiring my solar panels (8 - 100W panels) from all-parallel to a series-to-parallel configuration and installing a breaker on both +/- incoming solar cables so both can be easily turned on/off simultaneously.

Thank you, thank you, once again for your most gracious guidance.

If there is something obviously (to you) very wrong with my info above, and you have a moment for a brief response, it will again be appreciated. But, you have already done a lot to help me, so please do not feel obligated.

You have my enduring heartfelt thanks.

Jim S.
 

mikefitz

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May 28, 2020
Messages
887
Blue sea breakers are good, they are usually rebranded Bussmann, a quality product.
You seem to have the wire size correct and as you say there is no harm in using a larger cable that needed.
With low voltage DC systems its usual that the cable is selected to reduce the volt drop in the cable, 0.5 volt drop in a 12v system has more effect than the same drop in a 110 system.

There are various guides to selecting cable size, there are some in the resources section, this is from BlueSea,


bluesea chart.jpg

Mike
 
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