What exactly starts happening when batteries begin to reach very high numbers of charge cycles?

[betterthanyou]

Do they simply not hold a charge as long?

For example with a battery such as this:
SONY VTC4 18650 2000mAh Battery - Flat Top - 30A

max continuous discharging current: 30A
voltage: 3.8
full charge voltage: 4.2v

So after a very significant number of recharge cycles, is the only effect that the battery holds a charge for a lesser amount of time? Could it influence other things, such as the batteries voltage output? Could it cause the battery some type of delay before it starts putting out power/and or dropoff in power towards the end of firing it?

 

[Bunnykiller]

you will see a significant drop in usage time kinda like a 3400mAh battery new slowly dies off to a 1000mAh battery, still takes a full voltage charge but will last 1/2 the time it used to.

 

[Ryedan]

Do they simply not hold a charge as long?

For example with a battery such as this:
SONY VTC4 18650 2000mAh Battery - Flat Top - 30A

max continuous discharging current: 30A
voltage: 3.8
full charge voltage: 4.2v

So after a very significant number of recharge cycles, is the only effect that the battery holds a charge for a lesser amount of time? Could it influence other things, such as the batteries voltage output? Could it cause the battery some type of delay before it starts putting out power/and or dropoff in power towards the end of firing it?

Chemical changes inside the battery. Internal resistance goes up, voltage drop under load goes up, mAh goes down significantly, it will discharge faster while not being used and the maximum amp limit goes down. Not sure about voltage off the charger.

I've never heard of delays on power on, but if it's putting out less power that would feel like a delay. Voltage drop increases the longer the battery is being fired and that might get worse, but that's my opinion only.