How to test a battery cable?

Post by **scot850** » 15 Feb 2024, 19:13

I have seen/read stuff on this, but how do you test a battery cable to know if it is good? As anyone who knows and has removed one of these cables, it is a major pain as Volvo routes the +ve cable though a couple of metal ties that have to be removed, but then also through the main wiring harness at the bottom of the radiator. To remove it requires taking 2 x M6 bolts out of the top of the front engine mount and then using a pair of channel locks to try to fight the 2 tanks on the top of the cover to remove it. Then you have to cut open a plastic corrugated shroud over the wiring and then finally, cutting through a bunch of electrical tape before disconnecting the wire at the starter.

Finally you can remove the cable.

It would be good to know if the cable was good before doing all this for nothing. I cleaned the cable I pulled yesterday and then tested the continuity which read 0 ohms. Is that of any use as a measurement?

Is the only way to measure this and get a true reading of the cable being good is to fit it and then see if it heats up and do a voltage drop test? If so, what does a good cable read?

Thanks,

Neil.

Post by **abscate** » 15 Feb 2024, 19:39

You can’t test a battery cable with a VOM unless you have a mega sensitive one which no one here can afford.

So, you out the headlights on, and measure the voltage at the battery and at the main bus wire on the fuse box and report back the voltages to 4 significant figures

Post by **scot850** » 15 Feb 2024, 21:15

That doesn't work on a junkyard car or on a cable not mounted in a car though.

Neil.

Post by **misha** » 16 Feb 2024, 03:41

You can't really test it when it's removed from a car and not have a voltage and heat load on it.
Even the worst one will check out ok when you start the car and take voltage drop test right away.

It needs to be in a hot enviroment(engine heat)with a voltage load on it at least for 30 min and without turning the engine off prior to voltage drop test.
Then it shows it's weakness.

Post by **ZionXIX** » 16 Feb 2024, 07:52

It sounds like it's cheaper and easier to just replace or rebuild the cable.

Post by **volvolugnut** » 16 Feb 2024, 08:16

I think we are COLLECTIVELY smart enough to come up with a good test for the battery cable that does not require removing the cable, big bucks, and lots of equipment.
Something like a test load with cheap voltage tester.
Ideas?
volvolugnut

Post by **abscate** » 16 Feb 2024, 08:56

ZionXIX wrote: ↑16 Feb 2024, 07:52 It sounds like it's cheaper and easier to just replace or rebuild the cable.

You dont have too many Scots down in TX, do you?

Noooooooooooooo.

By the time I lug a battery, a headlight, and clips to rig a junkyard tester, I would have clicked on Ancor wire, lugs, and made my own.

Post by **volvolugnut** » 16 Feb 2024, 09:05

Something like this to test battery cable in car:
The equipment:
A known fixed load: Headlight? Fan? Heater strip? Should be cheap and easily obtained.
An external wire for voltage drop reference to ground. Long enough to reach from battery to starter.
A voltage meter, digital.
The test:
If the cable to be tested does not have a battery attached (such as a salvage yard car), bring a known good battery for the test.
Connect the external wire to the battery ground.
Remove the cable from the starter and connect the load between the starter cable and the ground at the starter.
Measure voltage drop between ground at the battery and again at the load end of the cable.
Compare the two voltages to known good cable information.
Can this work?
volvolugnut

Post by **volvolugnut** » 16 Feb 2024, 09:07

Some people just don't like science projects.

volvolugnutr

Post by **scot850** » 16 Feb 2024, 10:22

I have a 0-30V DC power supply. Could I use that by connecting either end of the cable, or do I need something like a headlight to load the cable to see if the voltage drops?

I have various headlights or cabin fan motors I could use as a load?

I have loads of parts I could use. Sure, I could just make up a cable, but I like the end clamps on the Volvo cables as apposed to the regular battery clamps.

I might just sacrifice this cable and see if the batter cable end can be removed. Got to think it is swaged on as the other end for the starter motor is just crimped. Can't see them soldering the top end. Other option is as has been mentioned elsewhere, to cut the rubber heatshrink seal of the battery end, heat it up and flux the end, and then pour molten solder into the joint to improve connectivity, then reseal with heatshrink. Problem still comes on the how to test before/after to show improvement!

You guys are amazing, and thanks for taking the time to brainstorm this. All in the interest of helping others especially when more parts are going NLA almost daily!

Neil.