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Adequate fuse size for my battery system?

gac1222

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Joined
Mar 27, 2022
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Hey guys, planning on using a 200ah 12v Ampere time lithium battery for my van and using 2/0 wire to connect to my lynx distributor, then using 4awg wire to connect the distributor to the 1100 watt inverter. Will a 250amp fuse directly off the battery be sufficient to protect the 2/0 cables?
 
A main fuse should be 125% of your rated loads, class T recommended for lifepo4.

If your 1100W inverter is your max draw then consider a 150 to 175A fuse, and use 2awg wire for your inverter. It could draw as much as 120A.
120A X 125% = 150A.
200A X 125% = 250A.

Without knowing what other loads you have, this would cover the inverter.

I like this wire chart from BlueSea Systems as it's simple to check for voltage drop, ampacity, and wire size, all in one. As you can see, 2/0 wire is good for up to 200A.

DC_wire_selection_chartlg.jpg
 
A main fuse should be 125% of your rated loads, class T recommended for lifepo4.

If your 1100W inverter is your max draw then consider a 150 to 175A fuse, and use 2awg wire for your inverter. It could draw as much as 120A.
120A X 125% = 150A.
200A X 125% = 250A.

Without knowing what other loads you have, this would cover the inverter.

I like this wire chart from BlueSea Systems as it's simple to check for voltage drop, ampacity, and wire size, all in one. As you can see, 2/0 wire is good for up to 200A.

DC_wire_selection_chartlg.jpg

Yeah I was using the 4awg wire and 150a fuse for the inverter but that's simply because its the wire that came with it. The inverter will be my max draw.

I'm confused by the critical / non critical voltage drop. Wouldn't a further distance and more voltage drop (10%) equate to critical rather than non-critical?
 
I'm confused by the critical / non critical voltage drop. Wouldn't a further distance and more voltage drop (10%) equate to critical rather than non-critical?
Critical is things like the battery and the inverter. Non-critical is things like lights and fans. The idea is that you want less voltage drop for critical paths. Non-critical paths can handle a little bit more voltage drop.

So why do you plan 2/0AWG for the battery wires (which is more than large enough) but only 4AWG for the inverter? What else will be connected to the battery that results in as much load as the inverter? As stated, 2AWG would be a much better choice for the wires to the inverter. Never use wires that comes with an inverter. They give you the cheapest minimal junk they can get away with.
 
Critical is things like the battery and the inverter. Non-critical is things like lights and fans. The idea is that you want less voltage drop for critical paths. Non-critical paths can handle a little bit more voltage drop.

So why do you plan 2/0AWG for the battery wires (which is more than large enough) but only 4AWG for the inverter? What else will be connected to the battery that results in as much load as the inverter? As stated, 2AWG would be a much better choice for the wires to the inverter. Never use wires that comes with an inverter. They give you the cheapest minimal junk they can get away with.
Having this explained makes sense, I'll see if I can get some 2 awg wires for the inverter.
 
You can buy made-up cables, or you can get a crimper and lugs and make them yourself.
Out of all the sources for wire, the best one I found was ebay seller ACDCWIREANDSUPPLY: https://www.ebay.com/usr/acdcwireandsupply

Or you can buy from them directly. They have all the sizes and colors, in any length you want, at a decent price, and ship fast. Very nice welding-wire/battery wire type fine strand copper.

For my one install I bought a Tempco hammer crimper and happy with the way they turned out. For a lot of work, or heavy wire, a die-crimper makes a lot more sense. They're also very expensive.

The biggest downfall of DIY setups are the connections - if they're not done right it creates a lot of problems. And yeah, 4awg wire is 600w inverter size, perhaps up to a 1000W, but most will spec 2awg due to potential current draw at 12 volts.

I sawed one of my crimps in two to make sure I was getting good 'cold weld' in the crimp. Then heat-shrink them with proper adhesive type shrink tube.

 
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