Calculating wire size and voltage drop

You can have fatter wires from the farther away battery bank to the inverter than from the closer bank, to try to even up the amps flow from each bank when the inverter is on.

Mex, I run into residential wiring issues quite frequently, not due to smaller sized wire but from homeowners that decide to be electricians. My present work location has two runs of Romex wire-tied to the garage door rail and is looped across the garage ceiling. It disappears into the sheetrock of the front wall. I am not looking forward to straightening out that mess.

The inverter is installed within 1 1/2' of one battery bank. Due to physical limitations, the new, second bank will be within 6' of the inverter. That's the best I can do with this rig. I have a 1000w inverter so power demands aren't as large as some.

I would be putting the inverter as close to the batteries as possible!
Much smaller wire will carry the higher voltage, lower current AC.

Woe to the fool who gets caught selling off-spec AWG wire. Here in Mexico, wire is ALWAYS one number circular mil sized less than genuine wire. Use it in construction in the USA and the building inspector finds it (wire has spec numbers printed on it) and AWWWWWWWWWWWWAY the contractor goes. First to defend his license and secondly to civil and maybe criminal court. I have not come across counterfeit AWG in the USA but the SAE is laughable. Non rope stranded wire is ridiculously inferior for motor vehicle use. And note that welding cable is strictly regulated.

smkettner wrote:
So is the 90 amps split between the two wires? Sounds like 45 amps each or did I read that wrong?

Sorry, SM, missed your post. Maximum draw would be 90 A in a single phase.

I got a pretty fair deal on #1 welding cable--Flexaprene. The cross sectional area and resistance are almost AWG#1 but not quite. 780 strands of 30 ga. and resistance of .137 Ohms/ft..

MEXICOWANDERER wrote:
ALWAYS ALWAYS ALWAYS

Verify the gauge by getting the circular mil spec for that gauge. Too many errors re: SAE versus AWG. Someone claims they are selling "2 gauge wire" ask for the circular mil area of the conductor. If they refuse, drop the phone receiver back on the hook. AWG is about 4% larger, and is GUARANTEED to be a certain circular mil value. SAE is made in "Xhualung Province" and is guaranteed to have at least some copper and plastic in the product.

You are correct that AWG is larger than SAE, and can be so up to 10%. SAE also specifies the wire cross section.

But, SAE stands for Society of Automotive Engineers, and AWG stands for American Wire Gauge. Wire made to either of these standards can be made anywhere in the world. The insulation is a topic on its own, and can have many different descriptors. Don't just assume that SAE is bad and AWG is good. Nothing is guaranteed. You have to know the standard and the manufacturer, but made in North America or Europe is usually good. Elsewhere is ???

So is the 90 amps split between the two wires? Sounds like 45 amps each or did I read that wrong?

Good stuff, thanks guys! Yeah, I'm using Molex brand lugs and welding cable. I'm crimping and using heatshrink to seal the lug and wire connections. When all the battery terminations are completed, I'll break out the terminal sealer, not mil. spec. stuff but is working out OK for me on my vehicles.

I had planned to pull the two cables, a pair of 14 ga. (AC run) and the battery sensor wire through a 2" pipe, transversing the bottom of the trailer. I had forgotten about the propane pipe and a center frame gusset that will be in the way. New plan is to put it into EXN or some other type of loom.

Thanks for the heads up on AWG vs SAE and diameter, Mex. I've been buying a bit of stuff through Waytek Wire, mainly because they're local. They don't publish everything but a phone call is all that is needed.

ALWAYS ALWAYS ALWAYS

Verify the gauge by getting the circular mil spec for that gauge. Too many errors re: SAE versus AWG. Someone claims they are selling "2 gauge wire" ask for the circular mil area of the conductor. If they refuse, drop the phone receiver back on the hook. AWG is about 4% larger, and is GUARANTEED to be a certain circular mil value. SAE is made in "Xhualung Province" and is guaranteed to have at least some copper and plastic in the product.