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

D

Dave Baker

Jan 1, 1970
0
Does anyone know what would cause corrosion at the negative battery terminal
of a 7 amp/hour sealed lead acid battery?

There is a picture at
http://www.jodael.com/images/Corrosion.jpg
showing the damage.

This unit is in a protected place - maybe too protected as the box may be
getting too hot.

Is this caused by overcharging?

On a related note, I'm looking for some sort of modular battery charger that
can charge these batteries. It should be able to take 24V DC input, and
output whatever is needed to trickle charge the above battery. Anyone have
any sources for this kind of product? I'm going to need at least 10 of them.
Ideally they will be quite small (matchbox size or smaller) and rugged.

Dave

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C

CWatters

Jan 1, 1970
0
Dave Baker said:
Does anyone know what would cause corrosion at the negative battery terminal
of a 7 amp/hour sealed lead acid battery?

There is a picture at
http://www.jodael.com/images/Corrosion.jpg
showing the damage.

This unit is in a protected place - maybe too protected as the box may be
getting too hot.

Is this caused by overcharging?

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.
 
D

Dave Baker

Jan 1, 1970
0
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.

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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M

Michael

Jan 1, 1970
0
Dave said:
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.
 
C

CWatters

Jan 1, 1970
0
Michael said:
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.

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
 
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