2022 Leaf overcharging on timed L2 charger

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May 13, 2022
Davis, CA
I use the onboard timer to charge the 40 kWh battery to 80%. For the first 18 months I owned the car it reliably charged at the rate of 15% per hour, so four hours would take it from 20% to 80%. Recently that same 4 hour setting results in the battery ending near 100%. The other day the battery was at 46% and I set the EVSE for 2 hours. That should have taken it to 76% but instead it ended up at 96%. That amounts to 25% per hour or 10 kWh. Using Ohm's Law that amounts to 40 amps at 250 volts. The breaker on the EVSE is 30 amps so that charge rate for 2 hours is impossible. Is the timer not shutting off at the right time? Any ideas?
Your pack is no longer = 40kwh. The capacity has declined and degraded over time and mileage, such that you will need to adjust your calculatus eliminatus.

Your EVSE and OBC can supply ~6kWh of energy to the pack for each hour of charging--that is constant and doesn't change. But your Pack capacity is now about 25kWh instead of 40. So each hour of charging will replace 25% instead of the previous 15% per hour. Give it a try and see if my mathurbation is close to what you get.
+1 on these being potential symptoms of pack degradation, as unpalatable as that may be. I'm sorry for your loss.
You can check if the issue is caused by the Timer by setting it to the usual 2 hrs, then checking on it a few minutes after the 2-hour period to see if it is still charging. You may want to do this a few days in a row to get good test samples.

Otherwise, there's a long list of other items that could be causing it, including the EVSE itself or weak battery cells, so you may want to have your system checked.
I have a 2018, 40 kWh battery and it started out at 18% / hr and is now at 19% / hr. Try charging it on a day when you are home and can watch it. Time it for an hour and calculate the gain, then for another hour to prove to yourself that it is charging at a consistent % / hr rate. If it's consistent, then your charge timer may be messed up. I've never had my charge timer mess up but yours may be erratic?
Thank you all for your expertise. I closely monitored three timed charges hour by hour from 20% to 80%. Then I summarized the three charges by %gain in each hour. Historically it has taken 4 hours to go from 20 to 80%. In the first hour the average gain was 17-18%, the second hour was 15-16%, the third hour for all three charges was 15%, and the fourth varied between 10 and 15%. I don't know beans about lithium battery charging but my experience with more primitive batteries like lead acid or nickel metal hydride is that they accept more current when the state of charge is low and then taper off as the SOC increases. Is that the case here? The car is a 2 year old 2022 40 kWh Leaf with 7,000 miles. Leaf Spy reports SOH of 91.67%. The last quarterly battery report was mid march. The quarterly drops tend to be around 0.8%, although I lost 2% on the quarterly report 1 year ago. That's about all I know about this battery. Any thoughts? BTW I really like this car!
I have a 2018 40kwh (36kwh usable).

What is your real world range now? I cannot imagine your batter is below 30kwh capacity.

I would bet it's just an issue with timer. Your numbers you describe support this. I've given up trying to hold it to 80% charge. I just let it go to 100%.

I have personally had issues and difficulty setting the two separate schedules within the settings, and then mistaking which timer I had on or off. there is no timer on my car, just a charge schedule. Hopefully the 2022 settings are easier to navigate.

My car has a push button near the "open charge door" button to cancel the schedule. You may want to double check that this button/switch is not stuck closed.