Test for over charging battery?

Crispin

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So one of my new Mr-T batteries leaks a bit of "stuff" out of the vent hole. For the last month, it has also forms some corrosion around the negative terminal. Not much, about as high as a match head.
I poured some water / bi-carb on it and it's definitely electrolyte as there was lots of fizzing.

A call to my friendly parts man at Toyota to ask about this as it should be under warranty etc. He said the warranty covers dead batteries and this is probably due to over charging.
So, a quick test with meter and with the engine running, the battery is at 13.8 at idle, 14.0 / 14.1 when revving it.

Is 14v considered over charging?
Why would only one battery have a problem?
Out of interest, any reason it's the negative terminal with the corrosion? Is it a chemical / electrical thing (current flowing from positive to negative over the top of the battery / leaked electrolyte?) or is it just that that seal was weaker than the positive?
 

Steve Wright

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Mar 4, 2010
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Crispin said:
So one of my new Mr-T batteries leaks a bit of "stuff" out of the vent hole. For the last month, it has also forms some corrosion around the negative terminal. Not much, about as high as a match head.
I poured some water / bi-carb on it and it's definitely electrolyte as there was lots of fizzing.

A call to my friendly parts man at Toyota to ask about this as it should be under warranty etc. He said the warranty covers dead batteries and this is probably due to over charging.
So, a quick test with meter and with the engine running, the battery is at 13.8 at idle, 14.0 / 14.1 when revving it.

Is 14v considered over charging?
Why would only one battery have a problem?
Out of interest, any reason it's the negative terminal with the corrosion? Is it a chemical / electrical thing (current flowing from positive to negative over the top of the battery / leaked electrolyte?) or is it just that that seal was weaker than the positive?
Hi Crispin

14.1 Volts is not over charging at all (But) is that with everything switched off ?

You say you have two batteries, are they wired in parallel ? and are both batteries showing the same voltage when
the engine is running ??

as for the corrosion, make sure the connections are clean and tight, and check the connections at the other end of
the negative leads are good and tight, and as for tracking across the top of the battery ! I would not thing so, not at
12 volts

another test when the car is not running, test both batteries and see if are both the same voltage, as if one is a lot lower than the other that will cause a charging problem.

Also you say "one of your new batteries" did you get them as a pair ?

Steve
 

Crispin

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Slow reply.....Sorry :oops:

I measured with two other testers and for what it's worth, my 15 year old one seems to disagree with the other two. 14.2/14.3. Not exactly much of a difference.

Steve, yes, that was with everything off, engine idling.

I checked all connections and all are sound and clean. The corrosion is green deposits between the terminal and the battery case, not the terminal and the connector.

Both batteries are at the same voltage both when engine running and not.

The spares guy was correct when he asked "Is it the one closest to the alternator which has the problem?". It RH battery is connected to all alternator as well as the main loom in the car. The left (when looking at the car) simply has a large earth strap and a large cable going to the other positive terminal (they are connected in parallel).

Yes Steve, I bought them as a pair from Mr-T as the others were 5something years old and lost a charge after listening to the radio without the engine on. I don't recall them doing the same as this.
 

Steve Wright

Well-Known Member
I am in great_britain
Mar 4, 2010
364
34
48
Glossop
Crispin said:
Slow reply.....Sorry :oops:

I measured with two other testers and for what it's worth, my 15 year old one seems to disagree with the other two. 14.2/14.3. Not exactly much of a difference.

Steve, yes, that was with everything off, engine idling.

I checked all connections and all are sound and clean. The corrosion is green deposits between the terminal and the battery case, not the terminal and the connector.

Both batteries are at the same voltage both when engine running and not.

The spares guy was correct when he asked "Is it the one closest to the alternator which has the problem?". It RH battery is connected to all alternator as well as the main loom in the car. The left (when looking at the car) simply has a large earth strap and a large cable going to the other positive terminal (they are connected in parallel).

Yes Steve, I bought them as a pair from Mr-T as the others were 5something years old and lost a charge after listening to the radio without the engine on. I don't recall them doing the same as this.
Hi Again

One other thing to check:
Lift the +terminal of one of the batteries and the get your multimeter, and set on amps, and see if there is any current flow between the two batteries !

Steve
 
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Crispin

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Long time....

Ok, so the two batteries disconnected from each other have differing voltages of .2 (Should also have checked them each with the lights on for some load. :roll: )

Did a test for charging. After driving home for 30 miles the truck stood overnight with nothing on. In the morning started the engine off both batteries. Disconnected leaky one and put an ammeter on. It was pulling 7A for about 30 seconds then dropped to 4 and would not go lower. While this was happening it was sitting at the ±14.2V
A test on the second one did about the same although it did not hit 7 to start with but stayed around 5.5-6 and then tailed off to about 4A.

Is 4A a normal charging current for a battery?
 

Steve Wright

Well-Known Member
I am in great_britain
Mar 4, 2010
364
34
48
Glossop
Crispin said:
Long time....

Ok, so the two batteries disconnected from each other have differing voltages of .2 (Should also have checked them each with the lights on for some load. :roll: )

Did a test for charging. After driving home for 30 miles the truck stood overnight with nothing on. In the morning started the engine off both batteries. Disconnected leaky one and put an ammeter on. It was pulling 7A for about 30 seconds then dropped to 4 and would not go lower. While this was happening it was sitting at the ±14.2V
A test on the second one did about the same although it did not hit 7 to start with but stayed around 5.5-6 and then tailed off to about 4A.

Is 4A a normal charging current for a battery?

How did you measure the current ?

Steve
 

Crispin

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not sure what you mean "while connected to battery" :?

I started the car, disconnected the negative lead from one battery and then stuck the tester in series with that and the battery effectively reconnecting the battery to the car. The "normal" way to test current usage.
 
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