Solving a bad battery connection on a car.

softdown · December 3

This battery was disconnected for three years and charged on a regular basis. Its health is still acceptable.

Reconnected and found that I needed to scrub/sand/clean the positive connection every time I sought to start it. And it got worse each time. Had to scrub/sand/clean it after it sat for ONE hour.

Now no amount of scrubbing/sanding/cleaning will create a connection that allows the engine to turn over. Though radio etc have always worked fine.

I’ve never dealt with this phenomena. Seems very odd. Anybody know what is likely happening?

BB. · December 3

Sounds like the Battery is going weak/failing... And mostly starting on battery surface charge(?).

I have a daily driver car with a ~5 year old battery... Getting weak, but still starts car (mild climate, San Francisco area).

A pickup that had a 6-7 year old battery that was hardly driven, but on full time maintenance charge with this charger:

https://www.batteryminders.com/2012-12-volt-desulfating-battery-charger-worldwide-use

Has a "desulfating mode" that seemed to work OK--Although, I would not push desulfator vs just getting a good quality "float" charger.

Have several Battery Minders of this type, and one did fail after 5+ years--Second and third are still going fine.

-Bill

softdown · December 3

Seems logical. We’ll see how it responds to a truly full charge. If that works - time for a new battery!

softdown · December 5

Truly full charge made no difference. Recently tested ~600CCA which should be plenty for a 302CID engine. Guess I’ll try a different battery still.

manzanita2 · December 6

Did you clean the cable end too? Probably you did, but you didn't mention it.

johnsmith76 · December 7

It sounds like the battery itself may still be fine, but the positive terminal or cable likely has internal corrosion or damage that’s causing a high-resistance connection under load. That’s why small things like the radio work, but the moment the starter needs real current, the connection fails even after cleaning. Often the corrosion travels inside the cable under the insulation, so it looks clean on the outside but can’t carry amperage. At this point the best move is to replace the positive cable or terminal entirely, because if cleaning no longer restores a solid connection, the metal is probably too compromised to reliably carry starter current.

Wheelman55 · December 8

I had a “high end” stereo installer wire up a second battery for my truck. It failed miserably due to the fact that the installer used CCA cable instead of pure copper.

I learned to do all of my own wiring after that.

softdown · December 12

johnsmith76 said:

It sounds like the battery itself may still be fine, but the positive terminal or cable likely has internal corrosion or damage that’s causing a high-resistance connection under load. That’s why small things like the radio work, but the moment the starter needs real current, the connection fails even after cleaning. Often the corrosion travels inside the cable under the insulation, so it looks clean on the outside but can’t carry amperage. At this point the best move is to replace the positive cable or terminal entirely, because if cleaning no longer restores a solid connection, the metal is probably too compromised to reliably carry starter current.

Sounds very plausible given the batteries 630 CCA and 4.5 resistance. Yet replacing it yielded a couple easy starts so far.

manzanita2 · December 13

Btw, the specs for my 2013 truck's 302CID engine calls for a 750 CCA battery.

softdown · December 17

So far so good with battery replacement. Still say that 630 CCA should also have started it. It starts real easy as a rule.

softdown · December 17

manzanita2 said:

Did you clean the cable end too? Probably you did, but you didn't mention it.

Yes

Solving a bad battery connection on a car.

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