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Hi all, I have a 24kw Leaf, 2015. Generally it behaves well, range is excellent. Of late, when using a rapid charger (early hours of the morning, with the heater on) the SOC jumps from about 92/93% to 100% and the charge completes.

I've not managed to capture this whilst running leaf spy to see if the draw from the heater (being greater than the reported delivery of 1.83KW when I last glanced up) is causing a complete mis-read by the dashboard BMS and then it rectifies. Or if there is some kind of other issue that may be a bit better known in the community.

*and before anyone says it, yes I’m charging to 100% as I will work in my car, heating/aircon on with a baby keeping her asleep whilst my wife gets some rest. It’s the middle of the night, and no-one wants to use the chargers but I also need it to be charged for the wife to use the next day when I get back.
 

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Hi all, I have a 24kw Leaf, 2015. Generally it behaves well, range is excellent. Of late, when using a rapid charger (early hours of the morning, with the heater on) the SOC jumps from about 92/93% to 100% and the charge completes.

I've not managed to capture this whilst running leaf spy to see if the draw from the heater (being greater than the reported delivery of 1.83KW when I last glanced up)
Is your car one with a heat pump (I recall some 2015 didn't have them)?
 

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GOLF GTE PHEV
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Might it just be that the preset temperature has been reached so the heater switches off. The battery voltage will rise when this happens so the BMS shows 100%?

Mine did a somewhat similar thing this morning. It has finished the 4hour off peak and the app reported 99%.

I turned on the heating, inc the driver's seat which then showed 98% (main still connected and switched back on as usual when the heating is activated remotely).

A few minutes later when the preset 18C had been reached, the SOC jumped to 100%. Normally it takes about 3/4hr to get from 98 to 100%. (shame the gom showing 248miles couldn't be relied upon!)
 

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GOLF GTE PHEV
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Although unsure, I make an assumption that it does based on the lack of draw when the heater is on, and the excellent heat output. I guess I should research how to find out :)
The HP mainly maintains the temp. The NTC elemnt use a few kw to reach the preset temp quickly.
 

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GOLF GTE PHEV
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I suppose there could have been some balancing taking place when the SOC doesn't move for a while and then the BMS decides it's had enough.
 

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A jump in SoC at the start or end of a rapid charge session can be caused by the BMS having the wrong estimation of the SoH of the battery, this causes it to estimate the SoC inaccurately.

I used to see this a lot on my Peugeot Ion after the battery had degraded a lot - for example I'd arrive at a rapid charger with 35% SoC reported, (in Canion, as the dashboard only had 16 bars so was too coarse to notice this) as soon as I started a rapid charge the value would drop to 20%, the rapid charge would reach 74% then end, then the figure would suddenly jump to 82%. (Which is where the Peugeot Ion should normally stop on a rapid charger)

Different car but similar Lithium Ion battery monitoring/management principles.

In simple terms, very low and very high SoC's are measured using voltage estimation - in between SoC is estimated using Coulomb counting, where the BMS counts the number of Ah put in or taken out and together with an estimate of the usable capacity of the battery (which is of course affected by the SoH) it tries to keep track of the SoC.

However if the BMS thinks the usable capacity (and therefore SoH) is better than it really is it will find that maximum charge voltage is reached sooner than it expected. So in your case you got to what it thought was 92% then reached the maximum voltage and at that point it had no choice but to update the SoC instantly to 100%.

If you tend to stay away from the bottom and/or top of the battery the SoH figure might be out by quite a bit now and this may cause weird jumps in SoC at both ends. A couple of deeper discharge/charge cycles may correct this but don't be upset if the reported SoH figure drops in the process.
 
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