2020 Model 3 LR never stops charging [resolved]

[Scelto]

Hi all,

I had a good search here and across the Internet as a whole, but didn't see anything quite like this.

In June, the family ICE car was destroyed in a flood and we decided to replace it with a Model 3. The waiting list at the time was stretching into 4+ months and with only one family car (now written off and undrivable) we were stuck in an insurance-provided rental that simply wouldn't stretch that long!

Anyway we found a 5,000 mile Model 3 LR with the acceleration boost available immediately for pretty much the same price as a brand new model, and given our time constraints decided to buy it.

With long day trips and a couple of long weekends away, we've put a little over 2,500 miles on it since picking it up with a combination of short and long trips.

One one of the trips I decided to charge to 100% at a supercharger, but charging literally never finished. We sat with the charge *showing* 100% but never "completing" for over 25 minutes before giving up and driving on with an indicated range of 299 miles.

I tried unplugging the charger and plugging it back in again, forcing a "shut down" from the screen, making sure the apps weren't connecting and keeping the car alive, all to no avail.

After that trip, I went through the palarva of a "BMS reset", letting the SoC get down to 6% and then supercharging to 100%.

The same happened again - charging never finished. It trickled down to 1kW (on a supercharger) but never finished.

The following weekend I did another BMS reset (for whatever that's actually worth), letting the charge get down to 1% this time and the same thing happened again. This time I waited 30 minutes with SoC showing 100% but never finishing, trickling at 1kW.

The Tessie app thinks the battery capacity is actually getting worse:

I do understand that range and even SoC to an extent is an "educated guess" but has anyone else had the problem where their car just never completes charging?

FWIW, there are no warning messages at all, the car is completely standard on 18" Aero wheels, and has been Supercharged five times (twice to 80%, thrice to 100%, two of those as part of the "BMS reset") since I bought it. The rest of the time it charges off level 1 (110v) in my garage. I do not leave it plugged in all the time, instead charging to 80% and using it to ~50% before plugging it in again.

Any thoughts?

Cheers!

 

[RayK]

So, the problem of never stopping the charge is only when it's set to 100%. If set to a maximum of 80% or other non-100% setting, it does stop, yes?

I would try doing a forced reboot; hold the two steering wheel buttons in for about 30-35 seconds until you see the Tesla logo on the screen and then release the buttons. See if that fixes things. You can also contact Service and ask if they can see anything in the logs. You'll probably have to give them the exact date/time of when you see the problem.

 

[MountainRatMat]

This is completely normal. The battery is rebalancing at 100% and it can take a looooooong time. My advice, when you have enough range to complete your trip just unplug, go, and don't worry about it. The BMS will do it's thing over time. Draining and fully charging the battery only recalibrates the BMS but you aren't getting any magic extra range back when you do that.

Range will decrease a bit, especially in the first 10k miles, but after that the degradation will level off.

It's a very different way of thinking from an ICE car but the Tesla BMS is second to none and just let it do it's thing.

Letting the car sit will also level out the BMS over time.

 

[Tam]

....their car just never completes charging?

It's just like watching the paint dry for 30 minutes then proclaiming that it's still wet and will never be dry.

When you want to complete 100%, leave it plugged in and go to sleep for a good restful night. When you wake up in the morning, you'll notice the "complete " message was done during the night.

If you don't want to watch the paint dry, then don't watch your car to complete 100% charge, especially at a Supercharger. That’s an abuse of time that’s meant for quick turn over.

...I do not leave it plugged in all the time....

That's contrary to your owner's manual.

, instead charging to 80% and using it to ~50% before plugging it in again.

That's contrary to your owner's manual. Please plug in and charge when you can and don't wait.

 

[Frank99]

It takes a long time to get to 100%. Perhaps you just weren't patient enough at the supercharger. Another option is that your car may have been taking significant power at the supercharger - maybe you were sitting in it (keeps the computers running) with the A/C on, and the Supercharger was simply providing enough current to keep that going? What happens if you turn off summon, sentry, and overheat protection and get out of the car and go to lunch with the car charging?

In any case, it doesn't really matter. It's a curiosity that the car doesn't say "Charging complete", but is unlikely to be a significant issue.

I do have another suggestion. Charge your car to 90% at the supercharger (because you say use 120V at home), then take it home and plug it in overnight with the charge limit set to 100%. When you come out in the morning, charging should be stopped. This should allow the car to do all the housekeeping that it may need to do (balancing the battery cells, determining the full capacity of the cells, etc) while you sleep. This might resolve the issue.

Then stop charging to 100%. I did it a number of times when I first got the car when I was playing with it, but just haven't felt the need for the last year or two. It turns out that I never need the extra 10% because on long road trips the first Supercharger I need to stop at after leaving home is the same whether I charge to 80, 90, or 100%. And when travelling, you'd almost never wait for the car to charge to 100% either.

<edit> and Ninja'ed by Tam and MountainRatMat.
Although I wouldn't remonstrate with Scelto about his charging scheme - it's perfectly fine.

 

[Tam]

...letting the charge get down to 1% this time...

There is a reason that your owner's manual warns against driving with low state of charge. It warns "damage" and cites the 12V battery.

What it didn’t explain was Ohm's law. In order for your motor to rotate, it needs minimum Power.

The formula is

Power = Voltage x Current.

At a lower state of charge, the Voltage drops. In order to get the same minimum Power to turn your motor, the formula would draw more Current from your cells. That torture stresses them out and that is not healthy for your battery.

 

[Tam]

...I did another BMS reset...

This practice has been warned against by Jerome Guillen I VP, WW sales and service in 2014. It's still valid in 2021:

BMS Drift - does it really matter?

...I don't know why you would say that... Because you can read from Jerome Guillen I (former VP, WW sales and service): "Thank you for your message and bringing this concern to my attention. Recently, some Model S owners have been concerned regarding displayed decreases in their vehicle's...

teslamotorsclub.com

 

[Frank99]

There is a reason that your owner's manual warns against driving with low state of charge. It warns "damage" and cites the 12V battery.

What it didn’t explain was the Ohm's law. In order for your motor to rotate, it need a minimum Power.

The formula is

Power = Voltage x Current.

At a lower state of charge, the Voltage drops. In order to get the same minimum Power to turn your motor, the formula would draw more Current from your cells. That torture stresses them out and that is not healthy for your battery.

Uhh, no.

You're right that, at lower voltages, you won't be able to get the same power out of the motor. The guys taking their cars to the dragstrip try to make sure to have a fully-charged battery when they hit it to maximize the power available.
Ohm's law, however, is not the right way to calculate current here. The inverter makes sure that the motor never becomes a simple resistor; it's always modulating the voltage to the motor to keep the core from saturating, so the motor should be modeled as an inductor where:
I = 1/L * (integral Vdt).
In essence, for a given accelerator position, a lower voltage will lead to a lower current from the battery and through the motor.

The caution against low states of charge is purely chemical. A lithium-ion battery goes through irreversible (=bad) chemical and mechanical processes when it gets to very low (or very high) states of charge. If you constantly drove your car down to 0% range, and charged to 100%, your battery would degrade much faster than driving down to 10% and charging to 90%, which would degrade just a little bit faster than driving down to 20% and charging to 80%. See A Generic Cycle Life Model for Lithium-Ion Batteries Based on Fatigue Theory and Equivalent Cycle Counting, figure 15 for an example of NMC batttery life versus depth of discharge, and BU-808: How to Prolong Lithium-based Batteries , table 2 and 4 for DOD and charge level graphs.

In addition, what Tesla is really worried about, IMHO, is all the bad things that can happen if you park the car at a low state of charge. If the main battery is nearly dead, it won't charge the 12V battery - which means that you may come out in the morning and find a dead car. If the main battery is nearly dead, it can't heat itself on a cold, cold night - and freezing the battery is not conducive to long life.

 

[Scelto]

Thanks for the reassurances that this is actually normal behaviour, even with supercharging.

Odd that I didn't come across that when searching though - maybe I really was just too impatient, with the expectation that charge would finish when the car reported 100% rather than continuing to charge at 1kW... seems odd to me. /shrug

I am aware of the many conflicting recommendations and suggestions around charging regimes and the (possibly well intentioned) remonstrations about "wasting time" and RTFM are water off a duck's back. The BMS "reset" was also suggested to me by a SC tech, especially now knowing the 14 month charging history of the car before I bought it.

But I know pretty much everything is pure conjecture. Even the recommendations in the owner's guide...

I will try @Frank99's suggestion to just set 100% charge at home and let it do its thing for as long as it needs. At least up to some reasonable time measured in small number of hours!

I didn't do that before because literally the only thing I found in my research that was consistent is that it's bad to leave the battery sitting at 100% SoC

I work from home though, so will trickle it up to 100% during waking hours and take it for a 10% drive if it ever shows "complete".

Thanks again everybody.

 

[Scelto]

*NOT knowing the charging history

 

[Frank99]

I didn't do that before because literally the only thing I found in my research that was consistent is that it's bad to leave the battery sitting at 100% SoC

"bad" is a relative term. It's bad in the sense that it might reduce your range by 0.01% - so if you do it 1000 times, you might reduce your range by 10%. If you do it once, it's...0.01%. Probably worth it to see if it solves the problem.

You can have the car notify the Tesla app on your phone when it's done charging. Look under Settings->Notifications.

 

[jjrandorin]

OP others already covered this, but its 100% normal. Its balancing the battery / cells at 100%. Dont do it at a supercharger (there isnt any point to waiting for the battery to balance at a supercharger).

Do it when you are at home, overnight, as someone else mentioned, before a drive to work or something. It may take 10 minutes, it may take an hour. As @Frank99 mentions, just dont leave it like that for days. Do it before you have a drive you will be doing that will be at least 7-10% of your battery.

Or, dont, if you dont want to, the cells get out of balance, but you dont have to do any of that if you dont want to.

 

[Scelto]

Absent a working thanks button (newbie restriction?), I'll say thanks again here.

I do have charging notifications enabled and get the "almost complete" and "completed" messages for all states of charge below 100%. I still get "almost complete" messages for 100%, but never "completed", and that's consistent with my observation that charging really never ends (so far), with a 1kW charge continuing to show.

I've set it to charge to 100% on my level 1 charger at home and it should "finish" at about 10pm today.

I'll check it when I wake up tomorrow and if it's finished I'll go for a drive.

If it hasn't finished, I'll leave it going until 6pm (18 hours to rebalance, or whatever magic is going on) then take it for a drive anyway and plan a trip to a service center to see if they can find out why it never actually finishes.

I'll post whatever happens in case somebody with a similar problem comes across this thread in future.

Cheers,
Scelto.

 

[MountainRatMat]

Absent a working thanks button (newbie restriction?), I'll say thanks again here.

I do have charging notifications enabled and get the "almost complete" and "completed" messages for all states of charge below 100%. I still get "almost complete" messages for 100%, but never "completed", and that's consistent with my observation that charging really never ends (so far), with a 1kW charge continuing to show.

I've set it to charge to 100% on my level 1 charger at home and it should "finish" at about 10pm today.

I'll check it when I wake up tomorrow and if it's finished I'll go for a drive.

If it hasn't finished, I'll leave it going until 6pm (18 hours to rebalance, or whatever magic is going on) then take it for a drive anyway and plan a trip to a service center to see if they can find out why it never actually finishes.

I'll post whatever happens in case somebody with a similar problem comes across this thread in future.

Cheers,
Scelto.

Service Center can do nothing about this. It is normal operation for the car.

 

[jjrandorin]

it will finish eventually (and when it finally does finish, the next time you charge to 100% it wont take as long to finish, but may still sit there for some amount of time).

Its not necessary to re balance the cells often or anything, but if you are going on a trip anyway, its a good idea to charge to 100% before you start your journey, including letting the cells balance (so charging overnight is normally what we recommend).

Since it appears you are charging on level 1 at home, and driving more than you can charge in an overnight period (thus supplementing with supercharging?), replace "charge overnight" with "let sit at 100% till it says complete while at home". you may be driving more than an "overnight" charge can replace on L1 charging.

it will finish eventually (and when it finally does finish, the next time you charge to 100% it wont take as long to finish, but may still sit there for some amount of time).

Its not necessary to re balance the cells often or anything, but if you are going on a trip anyway, its a good idea to charge to 100% before you start your journey, including letting the cells balance (so charging overnight is normally what we recommend).

Since it appears you are charging on level 1 at home, and driving more than you can charge in an overnight period (thus supplementing with supercharging?), replace "charge overnight" with "let sit at 100% till it says complete while at home". you may be driving more than an "overnight" charge can replace on L1 charging.

Absent a working thanks button (newbie restriction?), I'll say thanks again here.

Those features appear for new users after some amount of minimum posts. I dont know the exact number (I am a volunteer mod like most of the other mods here, so dont set that number) but believe its somewhere around 10 or so.

 

[Scelto]

I charged KITT overnight on Friday.

I started charging after a short drive at 9:45pm with 93% SoC (having interrupted the slow charge to 100%) and didn't check it again until I woke up at about 6:30am on Saturday.

It did in fact report "Completed" just before 5am (so 7 hours after charging started), and looking at the Tessie app it looks like it spent about 3 hours at an actual 100% SoC before giving in and admitting it was done.

So that particular mystery is... erm... solved?- thanks to all who gave me useful advice there!

At 100% the car shows a range of 299 miles but I've done a lot of short and... enthusiastic... drives (300-600kWh) covering a total of about 250 miles in which I understand plays into that mystery calculation so I'm not seeing any obvious problem after all!

Thanks again everybody

 

[Scelto]

Oh, I forgot to address one thing:

>Since it appears you are charging on level 1 at home, and driving more than you can charge in an overnight period

That's not the case actually. I do use level 1, but it's more than enough.

My wife and I work from home and my son walks to school, so we have no actual need of the car most days - apart from grocery shopping our daily miles are just for fun, and usually less than 10 miles/day averaged over the "working" week.

We do try to get out at weekends though - summer is short here in Chicago - and that's when we supercharge en route, driving up to ~4 hours each way and typically supercharging - to less than 100% - once in each direction.

I actually bought the level 2 charger and was ready to have my electrician install it when I realized in the first two weeks that we just don't need it so sent it back for a refund!

Cheers,
Scelto
(a Brit in Chicago)

 

[Frank99]

Great to hear.

 

[drtimhill]

But I know pretty much everything is pure conjecture. Even the recommendations in the owner's guide...

The basics are a bit more than conjecture, as others have noted in the thread, it's based on battery fundamentals. Essentially, if you want to be stress-free, it comes down to keeping the car in the 90% to 10% band, or if you want to be really conservative, the 80% to 20% band. Charge when you can (you dont have to "deep cycle" the battery, regular daily top-ups are fine), and dont fret about a 100% charge when you need it for peace of mind on a long trip. That's it really.

 

[drtimhill]

I actually bought the level 2 charger and was ready to have my electrician install it when I realized in the first two weeks that we just don't need it so sent it back for a refund!

But you might want to think about the economics long term. For various reasons, the car has a fixed overhead power-draw while charging, in addition to the actual energy its putting into the battery. With L1 charging, this fixed overhead is a significant percentage of the total power coming from the wall outlet. This means that, for a given number of miles of range added to the battery, you will use less energy (and less $$ on your electric bill) when using L2 charging vs L1. So long-term you might (depending on your driving habits) end up saving money (and the environment a bit as well) by going the L2 route, even after you factor in the L2 charger purchase.