Battery cables 4-0 seems like overkill

[cruisintoo]

My 48 year old battery cables are failing. I cannot find what the amperage draw on my Delco Remy starter is. The run from 8 D batteries to starter is about 12 feet. My mechanic feels like 4 0 is unnecessary and probably2 0 would suffice. Any info would be greatly appreciated

[Avenger]

So, a 24 foot circuit? There's tables for that sort of thing, but if it had 4/0 it probably needs 4/0.

[CMeacham]

That seems to me to be an absolute horrible place to try to save a dollar.

I would keep it 4/0.

[Pascal]

I will never try to spare a buck by downsizing wires. Not worth it. I pretty much use 4/0 on every DC battery cable …

Plus if you are paying someone to replace a battery cable, the cable costs is nothing compared to the labor

[Play'N Hooky Too]

Keep the 4/0 wire....replace the mechanic.

[Captain Ralph]

Keep the 4/0 wire....replace the mechanic.

Let me retype that slower for the reading impaired;
Keep the 4/0 wire....replace the mechanic

[whoover]

If you don't mind crawling around it's an easy job to take on yourself. I did all of mine. I bought my hydraulic crimper on eBay, my lugs by the bag on Amazon (anchor) and my wire from local marine supply. I also ordered red and yellow shrink tube for the ends. Mine were so bad that I was using the cross over switch to start the engines, afterwards never a problem. 4/0 is the wire size, do not go smaller.

Walt Hoover

[sgharford]

The way I recall with electric motors, it has to do with the Full Load Amps (FLA) rating when you initially put power to them versus the the Run Load Amps (RLA) when an electric motor is actually running. The FLA draw is huge, albeit it only last for a second or 2 (why capacitors on some). Wire is sized by amperage so you go with the FLA rating of the motor. If you are going to do yourself, don't skimp on the crimper as suggested (would not recommend the type you 'hammer' shut), use commercial grade crimper as suggested. That was most memorable, and perhaps best, piece of advice I got on this forum 12 years ago from BoatsB when I was installing an inverter and dealing with allot of 4/0 wire. With inverters, way I recall, large wire size has to do with impedance. As aside, I always go at least one wire size larger then recommended with everything, saves allot of nuisance trips (like windlass) from happening.

As another aside - when you look at wire charts based on amperage and length, you take the full circuit round trip length, not just one way.

[q240z]

My old Constellation 52 with Detroit 671 naturals had OEM 2/0 cables that I replaced with 2/0. Never had a problem.

I have a longer cable run with my Roamer to Cummins 6CTAs, and it's 12vdc whereas the Connie was 32vdc, and the online wire size calculator said use 4/0, so that's what I did.

It's easy enough to measure the existing cables and plug the numbers into the online calculators. Going bigger than what the calculators recommend won't hurt anything but your wallet. Going smaller is a YUGE no-no.

[krush]

Cables don't wear out. Why are you told they need replacement?

Are they getting hot?