Are we sure that capacity is actually being lost?

[DaveEV]

Not necessarily, as there is a voltage temperature coefficient. This means that the OCV/SoC varies depending on temperature. So temperature must be taken into account when attempting to calculate SoC from OCV. There are numerous factors, one is that the battery ECU wants to reduce stress to an already hot pack, so even though it could charge to the same SoC, (this would show up as a higher voltage) it does not.

There's also an internal resistance temperature coefficient to take into consideration.

Right - I completely agree, but as I said above typically with Lithium batteries warmer temp = more capacity = lower internal resistance.

Perhaps the 100% voltage/temperature/gid data we have is incorrect or not accurate - hard to say - it doesn't appear that we have enough voltage data to really say at this point.

Hurry up and release your LEAFSCAN already so we can get more data!

 

[Ingineer]

I have found that once a "full" charge is finished, I have found that you can sometimes force more charging (and/or balancing) simply by leaving the EVSE connected and initiating a remote climate control activation through CarWings. Last time I tried this, charging had stopped at 20.2kWh stored with 259 gids showing. After activating the CC, I made it up to 22.3kWh with 280 gids after the climate control shut itself off.

This may be a good way to effect a more accurate capacity measurement if you have a gid meter.

-Phil

 

[GaslessInSeattle]

I've suspected this. When I was doing a lot of prewarming over the winter from 80%, it would add quite a bit of charge in the same amount of time it prewarmed from 100%. I concluded that prewarming allows over charging. seems like the same would be true for climate control/cooling in the summer accept that with high temperatures and high soc being a concern now, I wonder if 100% charging and then pre-cooling (overcharging) in hot climates isn't actually accelerating aging, particularly if this is happening several times a day. I also suspect that what folks are calling cell balancing, may, more times than not, be topping off as much as "balancing" and I've noticed that if left plugged in, the charger seems to "top off" multiple times... not sure if that's the blink being blinky or what but seeing multiple small charging attempts on the screen the next day after a 100% charge is not unusual. I'm just sharing my observations as such, I don't have the instrumentation or background that many of you have.

I have found that once a "full" charge is finished, I have found that you can sometimes force more charging (and/or balancing) simply by leaving the EVSE connected and initiating a remote climate control activation through CarWings. Last time I tried this, charging had stopped at 20.2kWh stored with 259 gids showing. After activating the CC, I made it up to 22.3kWh with 280 gids after the climate control shut itself off.

This may be a good way to effect a more accurate capacity measurement if you have a gid meter.

-Phil

 

[TonyWilliams]

Are we sure that capacity is actually being lost?

Yes I am certain my 13 month old LEAF with 17,000+ miles will not go as far as it used to.
Since new some charging days are better than others. I assume the better days are after the rebalance.

My 25,000 mile 13 month old car has a measured range reduction of about 13%. It has never, not even once, been exposed to temps over about 95F, and only a few times approached 95F. It just doesnt get that hot here, with mean temperature close to 72F.

Of course, I routinely have used the full available capacity of the battery. It does not sit at 100% charge for very long, and it is in a cool garage when charged late at night (mostly).

 

[palmermd]

It has never, not even once, been exposed to temps over about 95F, and that was only a few times.

You might want to reword or clarify this confusing sentence.

 

[TonyWilliams]

It has never, not even once, been exposed to temps over about 95F, and that was only a few times.

You might want to reword or clarify this confusing sentence.

Funny. I'll fix.

 

[abasile]

My 25,000 mile 13 month old car has a measured range reduction of about 13%. <snip> Of course, I routinely have used the full available capacity of the battery.

I suspect that particular LEAF might hold the record for the most "turtle" events. How many times did you turtle it? 20? I seem to recall you also ran down the battery until the car shut down on more than occasion.

My personal experience with Li-ion batteries in consumer electronics is that fully, or close to fully, draining a Li-ion battery is one of the very worst things you can do to it. If one must continue to drive after getting a "Very Low Battery" warning, it is advisable to use as little motor power as is safe.

Moral of the story: Try hard to avoid "turtling" your LEAF! It's already been done in the name of science.

 

[davewill]

... If one must continue to drive after getting a "Very Low Battery" warning, it is advisable to use as little motor power as is safe. ...

And try to get at least 2-3 bars of charge back in the car as soon as you can.

 

[DaveinOlyWA]

sorry late into this and postinf from phone so i maybe repeating things already said but

if you are that concerned, turn off timer or leave the end time open if you are TOU. any rebalacning that is needed will happen on its own.

also, the most you might see on rebalancing is 1-2% SOC. i am currently in the middle of my largest balancing adjustment ever (or at least since getting GID meter in Feb)

thurs charged to 272 GID
Sat charged to 276 GID
today charged to 279 GID
no charging other than listed

in all but today, car sat at least 3 hours before being unplugged. so sure it takes a bit and normally i see 280 on a regular basis but that is only 8/281 or 2.8%. now, the lowest # i had seen previously was 275. at first i thought this was my degradation starting but now it looks like i have a "reprieve"