-
Domestic Battery Cables
I just replaced one of my inverters so now I have a pure sine wave, sw3012 Xantrex (3000 watts) and a Xantrex 458 (2500 wattts). These inverters are paired with 8 8D AGM batteries. My new SW 3012 will be responsible for charging the batteries. The manual states that this inverter should have 4/0 cables connecting the inverter to the battery bank, but I currently have 2/0 (all lengths of cable are less than 4 feet). I have read many conflicting points of view about cable lengths, cable size, inverter size etc. I have two questions, should I change my cables to 4/0 and second, my batteries are linked with each other with 2 AWG cables; should these be upgraded and if so to what size. Thanks.
-
16 Replies
-
You do need 4/0 cables for a 3000W inverter at 12V. The nominal battery current is 250A. Actual current will be a bit higher due to losses in the inverter. 4/0 wire can carry 260A at 90deg C (pretty hot) single wire, unbundled. 2/0 wire can carry only 195A at same temperature.
At 12V all your batteries will be in parallel. Assuming your battery cables are connected to the first and last battery, the first and last inter-bank cables will carry the most current (250A – 250/8)=220A. The next inter-bank cable will carry 190A and so on.
2 gauge wire will be insufficient to carry your load within the battery bank (it can carry only 130A at 90 deg C). You’ll need at least 2/0 gauge.
Could you get away with smaller wires? Maybe, if you never use the full 3000W. But electrical fires are nasty. For peace of mind I’d spend the money to get new cables. Also, make sure all connections are tight and squeaky clean. Eight batteries is a lot of connections.
Hope this helps,
Gerald
Jeff and Lindsay
91 Marathon XL -
Isn’t 2/0 heavier than 4/0?
-
Wire ga. Goes down for heavier. goes up for heavier.
-
Gerald, thanks for the information. This is just what I needed. I have the new wires ordered.
-
-
Where did you order the cables?
Ron
-
Gerald, you recommend bringing all of the battery cables to 4/0?
Ron
-
Ron,
I’ve gotten cables made at my local West Marine store. They cut the wire
to match my old cables. They crimped and shrink wrapped the ends too.
-
Thanks, John.
-
There is no reason to install smaller cables. You 2/0 wires are larger than a 4/0 wire. There is no reason to make a change.
-
I just checked a wire size calculator. 4/0 wire is 0.4600 inches in diameter. 2/0 wire is 0.3648 inches in diameter.
Now you know for sure.
-
Never ever go with a smaller cable size than original equipment. There is no disadvantage to going larger, and in fact with larger cable there will be less heat and voltage drop. With smaller cable the risk of a fire is quite a bit higher.
I completely recabled a previous coach and went up a size. It was actually pretty cheap because I bought a spool of black and red cable. Then I got cable ends that get deformed to capture the cable and the tool to reconfigure the end was about $5 and all I had to do was strip the insulation back a little, insert the bare copper strands in the cable end, and then smash the cable end around the wire using the tool and a hammer. One smack with the hammer and it looked like it was done in a factory and there was no way to pull the cable out of the terminal end.
I replaced cables that were aged and that were showing a lot of green ugly corrosion around the copper strands that went into the original cable ends.
-
Ron,
I ordered my cables from this site: https://www.windynation.com/Welding-Battery-Cable
I had the cables cut, then crimped at Napa.
-
Hey Rudy 2 cable is bigger than 4. Me and the boys use to drag these around when I was a welding shop owner.
-
Log in to reply.