# Would any electrician among us take a look at my circuit



## sideKahr (Oct 15, 2014)

At present this is a 160 amp hour battery backup. I plan to expand it into a solar system, that's why the cables seem oversized. The last of my parts are in and this is the way I'll assemble it, unless someone tells me not to. All advice is appreciated.


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## SOCOM42 (Nov 9, 2012)

Why would you go with 2/0 between the batteries and 1/0 to the inverter?

The load is greater going to the inverter.

If you are running the charger between two parallel batteries no need to wire to both as shown.

I would not fuse the charger @ 60A, too high.


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## Back Pack Hack (Sep 15, 2016)

SOCOM42 said:


> Why would you go with 2/0 between the batteries and 1/0 to the inverter?
> 
> The load is greater going to the inverter.


Unless the future plan is to add capacity to the system. Add more batteries, then the existing cables between these two batteries can stay in place. Then replace the cables between the batteries and the inverter. Just a guess.



SOCOM42 said:


> I would not fuse the charger @ 60A, too high.


Yup.


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## sideKahr (Oct 15, 2014)

SOCOM42 said:


> ...I would not fuse the charger @ 60A, too high.


My logic was the 4 AWG cable is rated at 70 A, so a 60 A fuse should protect it. The charger itself has an internal 30 A fuse.

What do you think is the correct size? I'm new at this stuff.


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## SOCOM42 (Nov 9, 2012)

sideKahr said:


> My logic was the 4 AWG cable is rated at 70 A, so a 60 A fuse should protect it. The charger itself has an internal 30 A fuse.
> 
> What do you think is the correct size? I'm new at this stuff.


You should be looking at device protection, if it has a 30A fuse, putting an in line 60A is a waste of time.

The net result is the same even if you put in an extra 30A.

That internal is to protect the bridge circuit not the wiring.

An inline 30A fuse will react faster than the thermal listed below.

Batteries that sulfide out or otherwise go bad usually generate a dead short that will damage the charger.

The others in parallel with them can be dragged down to.

Some chargers have a thermal breaker that resets itself not a fuse or standard re-settable breaker.

Constantly tripping the thermal will result in damage also.

Those will keep switching itself on until the strip heats up and opens, you have to be aware of the chargers protection type.


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## 8301 (Nov 29, 2014)

The diagram will work fine. By placing a fuse at the + battery terminal the wire to the controller is protected if it was ever damaged. That fuse isn't required if the 12v wire to the inverter is in conduit but I put Blue Sea fuses at the battery bank as an additional safety.


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## 8301 (Nov 29, 2014)

double post


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## 8301 (Nov 29, 2014)

The diagram will work fine and the fuses are correctly sized but I also agree that the additional fuse between the charger and battery is redundant. If you still want it and the charger manufacturer believes 30 amps is the max safe level I'd go with a 30 amp fuse even if the wire is capable of handling 70 amps.


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## tango (Apr 12, 2013)

Fuses protect the wires, not the conponents


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## Back Pack Hack (Sep 15, 2016)

tango said:


> Fuses protect the wires, not the conponents


Fuses protect _everything_ downstream. They're not selective. If there's a short in the wires, the fuse opens. If there's a short in a device or component, the fuse opens. The fuse doesn't know and the fuse doesn't care.


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## SOCOM42 (Nov 9, 2012)

tango said:


> Fuses protect the wires, not the conponents


This applies to conventional structural electrical wiring not electronics.

There may be several fuses in a unit, none to protect the input line.

Generally, the power supply is the first item protected, and from low voltage draw.

Another example, I have 5-25 HP motors controlled by mag contactors,

If there is an overload on the motors or a leg drops out,

the thermal protection will drop the contactor, not the line fusing.


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## sideKahr (Oct 15, 2014)

This is the finished project. It's not pretty but it works. Solar panels next on the list.


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## SOCOM42 (Nov 9, 2012)

Neat little job, you even used grommets.

You do need a hydrometer to check the cells with.


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## sideKahr (Oct 15, 2014)

SOCOM42 said:


> Neat little job, you even used grommets.
> 
> You do need a hydrometer to check the cells with.


Thanks!

They're sealed batteries, AGM type. Maintenance free. No hydrogen in the basement, no acid on the floor.


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## SOCOM42 (Nov 9, 2012)

It looks like they have filler caps on them, what do I know?

I had six in a series-parallel circuit to operate a 24 volt R/T that was in one of my pictures.

Had to constantly check each one, but that was 20 years ago, batteries have come a long way in my lifetime.


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