I am putting a battery disconnect in my dump. It has a Cat 3406b, with 3 group 31's, soon to be 4. A year ago a parts store sold me this: FR1044 - The Big Switch Batterty Shut-off Switch with Lock-Out and XL Terminals. Flaming River - Classic Auto Parts - Vintage Automobile Steering Components - Steering Accessories - Electrical Components www.flamingriver.com Is this switch enough? I see Waytek carries this: https://www.waytekwire.com/product/littelfuse-75908-battery-disconnect-switch?utm_source=google&utm_medium=cpc&utm_campaign=22523071103&utm_term=&utm_content=&gad_source=1&gad_campaignid=22523071103&gbraid=0AAAAADzbIvYgmW6hJaHjtzSbmV7uzADad&gclid=CjwKCAjwnN3OBhA8EiwAfpTYekfLFZv9PHZzFqxObGZaaN_2Zv25-wSE0Bl7r0l7uTDmNbRRIlf9LRoCipgQAvD_BwE The Littlefuse switch rates for 2000 amps for 30 seconds, while the Flaming River unit rates for 2500 amps for 5 seconds. How much does this starter actually draw on cold startup?
That varies with temp and condition of starter, a good MT39 290 to 315. It's extended crank time that changes.
It's not an MT 39, I have one of those sitting on the shelf for two years now, but it's getting too late in the spring, so that isn't going to happen this year either. I don't really run this in the cold, when I do run on cold weather the truck runs out of the shop at 60°. Should I get a heavier disconnect switch?
I'm going gander you have a Delco MT42, those are designed up to 1650 amp draw on high side. But tested new on a torque bench tester those will pull 700 amps. So technically your switch is fine. The trouble with MT42's, it's a straight drive where the MT39 is gear reduction. Plus the MT39 can spin up to 33% faster, the 39 is way easier on batteries.
It will work fine. I’ve put a lot of similar disconnects in big equipment and never had a problem.
I always put the disconnect on the ground side. I've seen a lot of them put on the positive side, and I always think they get arced out with heavy starter draw.
Switching the ground side is good, if anything bumps up against it, it won't arc that way. The switch itself will not burn up any quicker on the positive or negative side of the circuit. Just as much amps have to return on the ground side to the battery as left the battery on the positive side.
I am planning on putting it on the ground side.
That’s a good switch. I’ve installed many of them. If you are going to run four batteries, I would split the grounds and use two switches. You could get by with 2/0 cable that way.