What Causes Overcharging and Excess Voltage in Car Batteries?

[versine]

Homework Statement

All other things being equal, are you more likely to "burn out" the starter motor on your automobile if the battery is overcharged or undercharged?

Relevant Equations

Faraday's law and motional emf

I'm pretty sure the answer is overcharged by intuition. Can someone provide a reason?

 

[phinds]

I think you're likely to ruin the battery by overcharging long before you could get to where it would hurt the starter (BUT ... I'm not an auto guy so take that w/ a grain of salt). I don't think overcharging raises the voltage level much, it just screws up the electrolyte.

If you're undercharged, I don't think that hurts the starter, you just won't start.

 

[hmmm27]

I'ma vote for undercharging

 

[versine]

I think you're likely to ruin the battery by overcharging long before you could get to where it would hurt the starter (BUT ... I'm not an auto guy so take that w/ a grain of salt). I don't think overcharging raises the voltage level much, it just screws up the electrolyte.

If you're undercharged, I don't think that hurts the starter, you just won't start.

from: https://itstillruns.com/causes-alternator-overcharge-7391992.html
"Alternators that overcharge will typically produce excess voltage to the battery, making the battery case swell up, become very hot and lose its electrolyte through boiling."

Can anyone explain why overcharging will produce excess voltage (and I assume undercharging will produce decreased voltage)?