Anomalous Shunt - Battery GIDs drop after plugging into level-1 charger when "full."

For two days now, I've noticed a weird behavior of my 2017 Leaf. If I unplug and replug my level-1 charger when the battery is above ~93% SOC leafspy (100% according to the dash), the traction battery will discharge... somewhere!

So I'm plugged in, but draining the traction battery from 98% > 93%, GIDs are dropping from 208 > 198. Where the heck is the energy going, and why?

The dashboard lights show charging, but leafspy reports a battery drain. The vehicle is off and parked with nothing running. I left it for an hour on two separate mornings and it drained from 98% down to 90-ish %, with a corresponding drop in GIDs.

The first morning, I unplugged and replugged at 97% and found it at 90% about 30 minutes later. Leafspy stayed connected and produced a 0 mile trip log said 278 drive and 60 charge, dropping 9 GIDs over 22 minutes. It also said 0 SHVolt, but I don't know what that is, though it usually reads near 400. Everything else looked nominal.

The second morning, I unplugged and replugged at 97% and found the same thing. Unplugged and replugged again at 93% and it continued to drain down to 92% in just a few minutes.

When the battery is depleted it seems to charge overnight just fine. Sometimes it cuts off earlier than I'd like, which is why I tried the re-plugging before leaving in the hour I have awake at home before leaving.

I have a very depleted 30 kWh battery (<60% SOH) and I'm waiting for a replacement.
I only have an onboard 3.6kW charger (no fast charging, and only half-speed level 2, if I stop at a station)

What the heck is this?! Where is the battery drain coming from? Where is the energy going? Obviously, I'm not going to be plugging in at high SOC anymore, but I'd like to know if this is some sort of charge management feature or a fault.

I can limp to work and back with 30 GIDs to spare out of 195, but I'd rather start reliably with all 207 remining GIDs.

Some other weirdness:
- I burn 50 GIDs on the way to work, but nearly 100 on the way back. I am against the wind and uphill and I drive maybe an average of 5mph faster, but I do sprint up to 75mph+ on the way home. It seems that speeds over 55 radically deplete the battery. Or are the GOM and leafspy just waaaaaaay off in their battery capacity estimates and the last third of the battery is much weaker than forecast (All GIDs are not created equal)?

- None of Leafspy's measurements seem to agree with each other. It tells me I have 15 kWh at the beginning of the day, burn 1.6+2.9+.18+.18+4.1 (9 kWh), and end the day with <3kWh. Last I checked 15 - 9 = 6, not 3. While driving, it will claim between 4 and 8 mi/kWh, VERY biased toward the high end most of the time. If I were getting the low end of that, (4kWh), I'd be burning 11.5 kWh. 15 - 11.5 = 3.5 remaining kWh, which is closer, but still not right.

Is my battery so badly wrecked that Leafspy can't accurately report on it? Am I getting cell dropouts or something similar that is killing my range at low SOC? Seems something like that. I have experience with this with NiCad batteries, but I don't know enough about LI batteries to diagnose.

Thoughts?

I don't recommend plugging in when the battery is already nearly full charge unless your battery is already deteriorated and you need all the range you can get. The LBC (lithium battery controller or BMS--battery management system) is protecting the battery just like it does not allow regeneration when the battery is fully charged. The battery is probably not really discharging--just the way state of charge is being reported by the LBC. I saw the same phenomenon with my 2011 when the original battery was down to 8 capacity bars and I would try to top it off before my morning commute.

GerryAZ said:

I don't recommend plugging in when the battery is already nearly full charge unless your battery is already deteriorated and you need all the range you can get. The LBC (lithium battery controller or BMS--battery management system) is protecting the battery just like it does not allow regeneration when the battery is fully charged. The battery is probably not really discharging--just the way state of charge is being reported by the LBC. I saw the same phenomenon with my 2011 when the original battery was down to 8 capacity bars and I would try to top it off before my morning commute.

Click to expand...

I think you're right. It's not like the LEAF has a "ground" where it can shunt battery. I was wondering if maybe it turned on battery heater or something, but simply a change in calculations is more likely. I did note that I ended the day much higher in charge than I would expect from starting 10% depleted. However, I drove VERY conservatively that day due to the low charge, and did cram in a kWh at a public charger where I walk my kids to school.

Today I let it charge normally and it started the day with 208 GIDs again.

I have my charger on a smartplug, which turns off during peak electricity hours. I think I had a Monday commute that also started at "90%" one day, and it was likely due to the charger turning "on" with a full battery and causing the "depletion" or recalculation. I need to reschedule my smartplug so that it charges to 50% at the beginning of the weekend, and then 100% Sunday night.

I need every GID I can get until I get a new battery. I'm down to 7 bars now. 56.7% SOH.

High speed really does obliterate kWh. I drove about 75 for a very short time and got 2.72 mi/kWh. Then I kept it mostly under 60 (and drafted behind an 18-wheeler when I was at 60) and got 5.4 mi/kWh!