We can crank and crank a stubborn internal combustion engine, until the lead-acid battery seems completely flat. Ah well, we think, we need an emergency rescue service. But if we waited for an hour or so, then we might find we can crank the engine again. We wrote this post to explain how batteries rebound and recover if we rest them for a while.
The Phenomenon of Battery Rebound and Recovery
Batteries recover after they appear to be flat, because they are putting their act back together again, although only slightly. Let’s consider another example, this time a zinc-carbon battery you could make as a school experiment, if you have an adult with you:
- Lay your hands on a zinc rod and a carbon rod.
- Partly immerse these rods carefully in sulfuric acid.
- Electrons flow between the rods, and then stop.
Why is this happening? It happens because hydrogen gas builds up on the carbon rod, and prevents the electrons flowing. However – and this is a simple example of how batteries rebound and recover – if we let our zinc-carbon battery rest for a while, then the gas dissipates and the electrons start flowing again.
The Chemistry Behind Batteries Rebounding (Slightly)
All batteries recover slightly after we place them under a heavy load. Here’s another view that explains the phenomenon that temporarily boosts them:
- Heavy electrical loads put pressure on battery chemistry to react faster.
- Reaction products accumulate around terminals slowing the chemistry.
- When a battery rests, these reaction products move away and dissipate.
- The chemical reaction continues a short while, increasing battery voltage.
However, this is not recharging in the true sense of the word. The battery does not actually gain energy. It merely recovers from the stress of a heavy load. This is how batteries appear to rebound and recover, although it is actually more of an illusion.
More Information
Can We Recover Energy From Spent Batteries?
