Cause of corrosion/salts on battery terminal? Battery charger modules?

terminal

No I believe it's caused by damp. I read somewhere that it's an electrolytic effect that produces acid and/or white lead oxide. Prevention usually involves covering the exposed terminal/wire with a layer of thick grease after connecting the leads.

Disconnect the lead and clean the terminal and contacts with a wire brush or file to remove any oxide, replace connection, tighten, test battery and then smear on some grease.

Well, the equipment is on a boat (although on an air-conditioned bridge of that boat, and in an IP67 box with goretex gland), but:

a) It's a sealed lead-acid battery so acid shouldn't be able to get out. Maybe not a good quality one?

b) The terminals on these small batteries (same as in UPS units or PABX units) aren't lead I don't think. And I'm just using normal spade connectors.

Dave

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SLAs that leak aren't unknown (which is not to say that yours definitely leak). Yours do live in a humid environment though; bare terminals is asking for trouble. I would carefully clean all connectors with fine abrasive (and a base solution, just in case), dry everything, reassemble, smear on Vaseline.

leak).

base

We've also seen this problem with NiCad cells used in model aircraft where it's known as the "black wire blues" because it frequently effects the negative lead but leaves the positive like new.

You asked:

"Does anyone know what would cause corrosion at the negative battery terminal of a 7 amp/hour sealed lead acid battery?"

It's often caused by the fumes being vented from the battery during charging. These consist of hydrogen and sulfate/sulfite compounds. Since the hydrogen is normally attracted to the negative terminal and the sulfate/sulfite (being negatively charged ions) to the positive terminal, your description of the problems is somewhat of an enigma so I would rule out this as a cause.

On the other hand, if you are in a very wet or damp environment, you could have what is essentially electroplating taking place with metalic ions migrating from the positive terminal to the negative terminal. This is rather unusual, but in a salt air marine environment is entirely plausable.

The solution to either cause is the same. Clean the connections and coat them with a heavy layer of ordinary grease. Ain't pretty, but it works.

Harry Conover