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my updated system diagram. submitted for your approval.

The shunt goes on the battery negative not the inverter negative.
 
updated w/ shunt and 400amp fuse at the fuse block

As drawn, that shunt will only measure the draw of the inverter and nothing else (making it pretty much useless). It needs to be located on the negative battery terminal and have all loads/charging circuits go through it.
 
right, so shunt between the busbar and battery negative?

Not the way you have that drawn. Just move the negative of the inverter to the top of the shunt.

Negative battery bank terminal -->shunt --> everything else
 
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@starchy do you really need a 3000 watt inverter?
3000 watts at 12 volts is a monster.
400 amps fault current is no joke.
We could make you a less expensive system with a 2000 watt inverter.
 
@starchy do you really need a 3000 watt inverter?
3000 watts at 12 volts is a monster.
400 amps fault current is no joke.
We could make you a less expensive system with a 2000 watt inveri
i already have the inverter. i was planning on building this months ago but got distracted with, well, every other aspect of the van build.
 
Curious about the spec for the 4/0 wire to the inverter. I have a 3000w inverter/charger that I plan to install to replace a 2000w inverter. A wire calc indicates that I can run 5' total wire length using #2 for 300A draw. The manual for my inverter/charger says recommended is 4/0 but no mention of run length so it seems they just spec the largest they can.
 

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Curious about the spec for the 4/0 wire to the inverter. I have a 3000w inverter/charger that I plan to install to replace a 2000w inverter. A wire calc indicates that I can run 5' total wire length using #2 for 300A draw. The manual for my inverter/charger says recommended is 4/0 but no mention of run length so it seems they just spec the largest they can.
Run length is about voltage drop.
AWG is about ampacity.

Have a look at the ampacity limits table here https://baymarinesupply.com/bosns_corner_wire_sizes
 
Run length is about voltage drop.
AWG is about ampacity.

Have a look at the ampacity limits table here https://baymarinesupply.com/bosns_corner_wire_sizes
That indicates that 2/0 to 4/0 is acceptable for 300A @ 12v. The 2/0 has a 1.2% drop which is fine for the inverter feed

Every chart and calculator uses length and acceptable drop to arrive at a wire size. Only the AC charts I found just show cable size for amps flowing.

http://circuitwizard.bluesea.com/ also shows 2/0 for 300A over 6' total wire length (3' pos, 3' gnd) and says for 6' @ 300A the 2/0 meets ABYC ampacity needs and #3 will handle it for 3% drop
 
That indicates that 2/0 to 4/0 is acceptable for 300A @ 12v. The 2/0 has a 1.2% drop which is fine for the inverter feed

Every chart and calculator uses length and acceptable drop to arrive at a wire size. Only the AC charts I found just show cable size for amps flowing.

http://circuitwizard.bluesea.com/ also shows 2/0 for 300A over 6' total wire length (3' pos, 3' gnd)
Yes but the 3000 watt inverter needs 400 amps fault ampacity.
I already showed the math earlier in the thread I believe.
 
Yes but the 3000 watt inverter needs 400 amps fault ampacity.
I already showed the math earlier in the thread I believe.
Thanks, I went back and looked at the calcs. So the inverter can draw 400A? In my system that wouldn't be able to last long as the BMS units can only supply 300A (150A ea)
 
Thanks, I went back and looked at the calcs. So the inverter can draw 400A? In my system that wouldn't be able to last long as the BMS units can only supply 300A (150A ea)
3000 ac watts / .85 conversion factor / 12 volts = 294.117647059 service amps
294.117647059 service amps / .8 fuse headroom = 367.647058824 fault amps

Service amps is the max current the inverter should draw under normal operating conditions.
But orthodoxy says to multiply the service current by 1.25 to arrive at fault current.
This is done to avoid nuisance trips.
 
ok, this is hurting my brainy bits. how 'bout now?
 

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