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)?

 

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.

 

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).

 

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.

 

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).

 

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.