What size bolt on fuse at the battery

[Heliman65]

Hi,
I'm having a bit of trouble working out what size bolt on fuse I require at my batteries...

My setup is:-

1x100w mono panel
30amp Epever tracer solar charger.
12 x12v fused box for my lighting.
Bus bar.
1 x 40amp breaker
8Awg cable controller side of the breaker.
4Amg cable from breaker + bus bar to battery

Batteries are:-
2 x 140ah 12v deep cycle marine/leisure
Which will be run in parallel.
The label on the Battery info:-
Type: L140
140Ah
1000 CCA
Deep Cycle


Any guidance would be very welcome...
I have to get this right as it's going to run all the lighting for 5 stables 3 out buildings 3 yard lights and the electric fence energiser...

Thanks in advance

 

[Steve_S]

The fuse is relative to the Inverter. We need to know your overall system voltage and what inverter you have and what it's rating is IE 100W / 2000W with surge etc… more info = better.

 

[kenkoh]

Hi,
I'm having a bit of trouble working out what size bolt on fuse I require at my batteries...

My setup is:-

1x100w mono panel
30amp Epever tracer solar charger.
12 x12v fused box for my lighting.
Bus bar.
1 x 40amp breaker
8Awg cable controller side of the breaker.
4Amg cable from breaker + bus bar to battery

Batteries are:-
2 x 140ah 12v deep cycle marine/leisure
Which will be run in parallel.
The label on the Battery info:-
Type: L140
140Ah
1000 CCA
Deep Cycle


Any guidance would be very welcome...
I have to get this right as it's going to run all the lighting for 5 stables 3 out buildings 3 yard lights and the electric fence energiser...

Thanks in advance

I made this chart for myself because I'm new and learning. I recieved a lot of help here so maybe this can help you. Remember, I'm new and not an expert, learning myself. Report any errors. https://www.evernote.com/shard/s719...5079a16189fd/97e4b6605a11f3dc030188d3beb909d4

 

[FilterGuy]

Does the

The fuse is relative to the Inverter.

The inverter is usually the largest load and often the only load, so that is a pretty good generalization. A more precise statement is that the fuse is relative to the load.

The only reason I even mention it is that the only thing even close to defining the load is "12 x12v fused box for my lighting"

 

[FilterGuy]

I assume this means the OP has a DC load other than an inverter.... Does the OP even have an inverter?

 

[FilterGuy]

With LiFePO4 where the discharge rate is typically 1C or less I would say the max size fuse would be 140*1.25= 175Amp. However, that would only be if the load needed 140 Amps and the wiring can handle 175Amp.....and that brings us back to what is the load?

 

[Heliman65]

I don't have an inverter it is a 12v lighting system with an electric fence energiser that is also 12v

 

[Heliman65]

Picture 1 is the 12 x 12v fused box
Picture 2 & 3 electric fence energiser
Picture 4 Battery info

 

[FilterGuy]

What I would do is measure the current with everything turned on, multiply it by 1.25 and call it good.

Some other points about fusing:

All wire that a fuse is going to protect must be sized to handle at least the amount off current of the fuse. That means if you tap off your main wire with a smaller wire, the main fuse must be small enough to protect the smaller wire *or* you need to add a smaller fuse where the smaller wire comes off the larger wire.

 

[FilterGuy]

I had to chuckle.... the fuse box is for a boat..... An electric fence on a boat????? Gotta keep those jumping sharks away!

 

[FilterGuy]

The electric fence uses almost nothing. Less than an amp. Do you know how much power your lights draw? Are they all LED?

 

[Heliman65]

What I would do is measure the current with everything turned on, multiply it by 1.25 and call it good.

Some other points about fusing:

All wire that a fuse is going to protect must be sized to handle at least the amount off current of the fuse. That means if you tap off your main wire with a smaller wire, the main fuse must be small enough to protect the smaller wire *or* you need to add a smaller fuse where the smaller wire comes off the larger wire.

Cool that makes sense 100% many thanks I'll give it a go... the horses and misses will appreciate bit of light in the stables as we are off grid regards and power..

Keep up the good work the youtube videos have got me this far.. ???

 

[Heliman65]

The electric fence uses almost nothing. Less than an amp. Do you know how much power your lights draw? Are they all LED?

Yes all LED 78w each light

 

[FilterGuy]

Yes all LED 78w each light

78W must be the "Incandescent equivalent" or they are some mighty big flood lights.

 

[Heliman65]

78W must be the "Incandescent equivalent" or they are some mighty big flood lights.

36 LED Per light SUV off road spot lights 12v/24v

 

[FilterGuy]

OK, so the current for each is 78W/12V=6.5A. So, take 6.5 x number of lights plus 1 for the electric fence, and that is your max current.

If you wire and fuse for 1.25 times the mac you should be safe.

Note: Your measured current will almost certainly be less than the calculated max so if you want to be ultra safe, wire for 1.25 times the max current and fuse for 1.25 times the measured current.

 

[JeepHammer]

8 AWG (8 Ga) conductor, 46A maximum,
45 Amp Fuse/Breaker Maximum.

4 AWG (4 Ga) conductor, 92A maximum,
90 Amp Fuse/Breaker Maximum.

The Fuse/Breaker does NOT protect the load or charge source, ect (Devices),
The Fuse/Breaker protects the wiring run and should be placed as close to 'power source' as possible.

Devices get separate fuse/breaker (best) attached to the device itself.

With cases like a breaker between battery & charge controller, both potentially power sources,
The fuse/breaker 'Hot' or 'Batt' (battery) terminal, the highest potential power source attaches to the 'Bat' or (+) terminal on the breaker.

Small breakers have one copper or brass stud, and one silver stud, the copper or brass is always the power side, the silver is always the Load side.

Larger breakers will be marked in different ways, most will have a (+) or 'Bat'/'Batt' terminal and a (-) or 'L' (Load) terminal. That's an L as in 'Load', not 'Line' as with AC breakers.