Positive battery terminal keeps turning black?

[johnny haywire]

I know this is probably a rookie question, but on my '78 280z, I have to pull the positive battery cable about every 10 days to clean/sand it off because the clamp and the terminal on the battery turn black (and the car won't start due to the bad connection). Fires right up after being cleaned, though.

I've had many cars over the years and have never dealt with this before.

One thing, though - the battery on the car seems to be too small. The guy I bought it from was likely looking to cut as many corners as possible to get her running and bought a very small battery for it. I have yet to replace the battery, but it's on the short list.

Also, the stereo is currently removed from the car, the clock does work, and the dome light bulb is out.

Will this corrosion on the terminal/cable go away when I get a proper battery for the Z?

[zKars]

Weird indeed. Not the norm at all. I can't see battery size being the issue. Something in the atmosphere is electro-plating those terminals. I wondering if the battery doesn't have a leak. Sprinkle a bit of baking soda around the terminal and see if you get any sizzling...

[MotoManMike]

Your terminal is seeping, some lead molds don't get all the bubbles out of the lead and they are pourous, what kind of battery is it? Lead acid? AGM?

[johnny haywire]

Thanks for the replies, guys. I'll do the baking soda trick and let you know what happens. I'll also check what kind of battery it is. The pourous terminal sounds like the culprit. Now that I think about it, the battery took a flop as well (my friend picked the car up for me in San Diego and when he stopped for fuel on the way home, the battery was off the tray (no hold down bits at all) and leaning against the block.

So, mostly likely that terminal is seeping and/or leaking.

This is good. I was worried that I might have a small electrical draw that was causing this.

[5thhorsemann]

Another thing to look at is some of the cheap battery terminals, specifically the non molded to the cable variety, are made of an alloy that reacts to pure lead and forms a hard black crusty oxidation at the interface of the clamp and lug, but not so much on the outside surfaces that are exposed. Clean the lugs and clamps and use the red battery terminal protector spray, this will also work if its a leaking problem, just follow the directions on the can...............Rookie................

[Wade Nelson]

Positive and negative terminals are actually slightly different sizes. Be sure you have the right one. Clamped down tight even air shouldn't be able to get in there and form oxides.

If you have a "repair" bolt-on terminal, toss it and go get a new manufactured cable or have a local shop make you one.

At this point you may have scrubbed enough lead / lead oxide off the terminal NOTHING will fit tight.

[madkaw]

Search custom battery cables on the forum- good alternative for battery cables that fit right and never have a problem with

[johnny haywire]

Thanks for all the tips, everyone. The cable and clamp seem to be in good condition and are not the cheap replacement types. Getting good purchase with the clamp isn't a problem, either. I'm thinking it's the terminal spewing a very slight but consistent amount. The current battery has about 2/3 the footprint of the OEM tray and hold down so I think I'll just replace it anyhow, but I will be sure to update the post once that's done.