Charge limit based on wattage

[stevenBowtie]

With the help of Emoncms, I caught my 2015 Leaf "packing" charge into the battery. When it reaches a normal fully charged state, it turns off for five minutes, charges another five, and repeats that cycle three times. Literature says it adds 0.7% capacity for that charge, but nothing about what it does to the battery long term. They ditched the option to limit charge to 80% in 2014 either because people complained that it hurt their range or because it didn't actually matter compared to other factors, I've not found consensus on this. Others have suggested using a time window to limit charge, but it seems rather ineffective in my use case. Looking at the graph, I think one could hit an arbitrary charge point between 65-90% by turning off at a specific wattage threshold. The bulk of the variation in the charge cycle is in the constant current phase, the constant voltage phase is almost the same every time regardless of how much energy was added to the battery.

TL;DR what is the most simple way to turn off the charge at a specific wattage threshold (ev_power)? At a glance I think using the web API and a Python script would get it done, but I would prefer not to add another computer to the mix.

Thanks!

[KipK]

It's probably your car BMS is balancing battery cells at the end of the charge.

[stevenBowtie]

That was my first thought, but according to the Nissan Leaf Forums/an old article (https://web.archive.org/web/20160316153329/http://insideevs.com/nissan-discusses-method-for-topping-off-leaf-battery/) it is to increase the total charge capacity. The article isn't great and doesn't go into any details aside from comparing it to pouring a beer and waiting for the foam to settle, which is arguably related to cell balancing. That brings up an interesting point, if the batteries are only being charged to 80% they can't be equalized effectively. I wonder if the factory "80% limit" option would fully charge the battery periodically? It would be trivial to do a full charge once a week to address it.

Background aside, my core question is can I feasibly add this to the firmware? What part of the source code should I look at to bodge in this feature. My guess is that the answer is "that's what the API/MQTT is for", but I thought it would be worth asking.