Is "surface charge" the proper term?

Thread Starter

#12

Joined Nov 30, 2010
18,167
A recent post contained the phrase, "surface charge" (on a car battery). I instinctively understood this term when I first heard it, but I don't know if it is a, "shade tree mechanic" term, or is it proper usage among the well educated (EE's)?
 

Lestraveled

Joined May 19, 2014
1,946
It is a valid term used in the battery industry. It is used to describe the voltage of an unloaded battery just after being charged, that is deceptively high. A batteries state is often determined by the "resting" voltage, which is the unloaded battery voltage after it has been loaded.
 

GopherT

Joined Nov 23, 2012
8,012
A recent post contained the phrase, "surface charge" (on a car battery). I instinctively understood this term when I first heard it, but I don't know if it is a, "shade tree mechanic" term, or is it proper usage among the well educated (EE's)?
I think it would be considered "gas recombination". A charging of a battery that is overcharging because there is no additional lead sulfate .


Gas recombination deals with electolysis of water (hydrogen and oxygen) and the oxygen (or lead oxide) playing a role in the subsequent lead acid electrochemical reaction. There are sealed batteries that take advantage of this reaction but I don't know the details ( if it is for durability or efficiency, or other).
 

Thread Starter

#12

Joined Nov 30, 2010
18,167
I don't think, "gas recombination" is going to result in effective communication, but if that's what Engineers call it, I'll just have to use the wrong term at the local car repair shop.:(
 

GopherT

Joined Nov 23, 2012
8,012
I don't think, "gas recombination" is going to result in effective communication, but if that's what Engineers call it, I'll just have to use the wrong term at the local car repair shop.:(
Correction, scientists/chemists call it gas recombination (what happens). The engineers have their own language - and may well call it surface charge (what is observed).
 

Lestraveled

Joined May 19, 2014
1,946
This is from a USA Battery website:
Surface charge is the uneven mixture of sulfuric acid and water within the surface of the plates as a result of charging or discharging. It will make a weak battery appear good or a good battery appear bad. You need to eliminate the surface charge by one of the following methods:

3.1. Allow the battery to sit for four to twelve hours to allow for the surface charge to dissipate.

3.2. Apply a load that is 33% of the ampere-hour capacity for five minutes and wait five to ten minutes.

3.3. With a battery load tester, apply a load of at least one half the battery's CCA rating for 15 seconds and wait five to ten minutes.
 
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