Can anyone explain what physically happens in a battery when charging it with a higher voltage and current than the nominal charging specs. I know it can reduce the battery lifetime/destroy but if anyone can explain what actually happens please do. Thanks

 

Hello,

What happens with a battery when there is to much voltage / current is depended on the type of battery.
On the site of batteruniversity you will find a lot of information:
http://www.batteryuniversity.com/

Bertus

 

The heat in the battery is increased as more voltage and current is added to it.

Heat is the primary killer.

If we are talking about lead-acid batteries, then what happen if charged 'faster' is:

The electrolyte heats, boils, and evaporates. As it evaporates, there is less liquid to keep things cool, so it heats faster and gets hotter..

Also the lead plates in these batteries can flake away an cause shorts inside the cell.

When talking about NiCAD or NiMH batteries, there is no liquid, but what happens is:

The paste can shrink from heating causing it to pull away from the anode. If it is no longer touching, then there is no longer a reaction or a way to pass electrons at that area.

This makes an area in the cell that is not producing any power.

It also increases the internal resistance of the cell. This leads to more heating even at proper charging levels.

In turn, more shrinkage, more material gets pulled away, and it goes on from there until replaced.

 

Aside from what Retched said higher voltage/currents combined with heat and the exaust gasses from the vaporized electrolyte will cause chemical reactions to take place which cause the chemistry to become inert. If proper charging is done to a cell then these chemical reactions never occur and the cell lasts a long time, which is why you're supposed to follow each manufacturers recommended charging and discharging methods, only they know the exact chemistry that's in their batteries and what it can tolerate reliably.