size of ground wire

[jBrew]

i have a battery bank of 4 x 12v 100ah
2S2P using 4awg wire to make a 24v 200ah bank

what would be the size of the ground wire from negative to frame of a van

 

[Samsonite801]

i have a battery bank of 4 x 12v 100ah
2S2P using 4awg wire to make a 24v 200ah bank

what would be the size of the ground wire from negative to frame of a van

What's the maximum amps you want to run through it under peak load?

 

[Short_Shot]

If it were me, it would get a 2/0 as short as is practical (< 3 feet) but if you have a smaller bms that may be overkill.

That's also kind of pricey if the budget is low.

 

[time2roll]

Same as the largest wire that leaves the battery.

 

[Boondock Saint]

Agree with 2/0 short run, and lots of clean contact area to frame.

Agree with "Same as largest wire . . ." to the extent that you may have multiple wires from a distribution point / busbar and if so I would also use 2/0 from the batts to that location on a short run.

If you go longer, go 3/0


.

 

[12VoltInstalls]

what would be the size of the ground wire from negative to frame of a van

yes, same size as the pos(+) cable
However:

You are assuming that the frame of the van is adequately grounded to the engine block/battery. It may not be. You should verify that..
And I’m assuming you’re trying to charge the batteries from the vehicle… Am I correct?

Verify the frame-to-block neg(-). The little flat braided ones from the factory- if that’s all that’s there- are only good for 60- optimistically 100A tops in many cases; an inverter rated at 1200W continuous is 100A load with a ~200A surge. That’s why you should verify the frame-tie cable.

 

[Short_Shot]

Always worth considering a full "big 3" upgrade from the car stereo world under the hood as well.

People claim the chassis just isn't a good ground due to resistance but frankly a large enough piece of steel is far better than any copper wire the average person likely to install. Hell. It's far better than the tiny cable the factory installed. And that's where the issue really is.

However as @12VoltInstalls points out you can correct that fairly easily.

Read this. Emphasis on "clean the connection points".

https://nvx.com/blog/how-to-install-a-big-3-upgrade/