What's this "Charge Cycle" talk?

[NV Ray]

So, supposedly Tesla's Li-ion HV battery is good for about 1500 charge cycles. And then what? Error message pops up?

What is a charge cycle exactly? My understanding it's cumulative 100% charges. i.e. 1 x 0-100% charge, 2 x 50%, and 5 x 20% charges all equal one charge cycle. How does an owner know how many charge cycles have been used?

 

[philly4]

Then it's expected the battery will be at around 70-80% of the original capacity.

No error will specifically pop up.

Your example of a charging cycle is correct.

As an owner you can get an estimate by taking your average kwh/mi and odometer and doing the math for how many charge cycles you've had.

As an example a M3LR is about 400-450k miles at 1500 charge cycles depending on your driving efficiency...so not something for most owners to ever worry about.

 

[Earl]

How does an owner know how many charge cycles have been used?

Charge cycles is just a approximation. The other factor on battery life is just plain calendar degredation over time. Its affected by many things, charge cycles and time are only the big ones. It's kind of like how many miles you'll get out of a gas engine - I've had them die at 70K miles and go over 200K.
As your car gets older, you'll notice that the range while full gets a little less over time.

 

[AAKEE]

So, supposedly Tesla's Li-ion HV battery is good for about 1500 charge cycles. And then what? Error message pops up?

What is a charge cycle exactly? My understanding it's cumulative 100% charges. i.e. 1 x 0-100% charge, 2 x 50%, and 5 x 20% charges all equal one charge cycle. How does an owner know how many charge cycles have been used?

To make it easy, Full Cycle Equivalent (FCE, or sometimes EFC) is the cumulative energy that corresponds to a 0-100% cycle as per your description above.
A cycle is charging and discharging, taking the cell back to the state before the cycle.
So just "cycle" can be any dept of discharge, for example 0-10-0%. We would need 10 of these to make one FCE.

You do not know the number of cycles. You can divide the energy used since new on the ODO with the battery size. Then you will have the approximate FCE number (but you will not know every single cycle). As battery selfdischarge a little and the energy used when not driving this calculated value will be slightly low.

Apps like Scan my Tesla present a cycle number but they just calculate it by using the total charged energy(that scan my tesla find from the BMS) with the current battery capacity. The charged energy is correct so with this solution the charged energy is correct.