My Model 3 never Stops Charging at Superchargers?

[ranss12]

I rarely charge to 100%, but I thought I’d do it today since I recently read that one should do it from time to time. The thing is, it never stopped charging. The miles got up to about 301, then the remaining time-to-charge jumped repeatedly between 20 and 25 minutes for about 15 minutes. During this 15 minutes the charging kW stayed at about 2kW but the range never increased above 301. During this 15 minutes the charge meter kept ticking up so that’s why after 15 minutes at 301 miles I called it quits and pulled the plug. Anyone have any idea what’s going on here? Is this normal? At least I’ll never get the fee for occupying a stall after charging is complete.

 

[Dana1]

I rarely charge to 100%, but I thought I’d do it today since I recently read that one should do it from time to time. The thing is, it never stopped charging. The miles got up to about 301, then the remaining time-to-charge jumped repeatedly between 20 and 25 minutes for about 15 minutes. During this 15 minutes the charging kW stayed at about 2kW but the range never increased above 301. During this 15 minutes the charge meter kept ticking up so that’s why after 15 minutes at 301 miles I called it quits and pulled the plug. Anyone have any idea what’s going on here? Is this normal? At least I’ll never get the fee for occupying a stall after charging is complete.

1 kw= 4.1 miles so, strange. At 2kw/hr I’d have though you’d see a two mile gain in 15 minutes. Mine has charged to 310 with my HPWC at home before long trips.

 

[ewoodrick]

Yep, that's pretty much the way it works.
The last part of the charging takes significantly longer than the remainder. 2kW is just above standard 120V charging.

In other words, it is bad etiquette to charge to 100% at Superchargers. You tie up a charger for a long period for which others can't use it.
Charge to 100% only at home.

Also, as it is topping off, it could be rebalancing the batteries and that takes time.

 

[mswlogo]

It takes a real long time to get to 100%

I think it may be balancing and when it is, it’s gonna make very little progress.

I’ve seen it take a full hour or more after 90% on a SC.

I’ve charged 100% twice. Once 3 months ago when I first got it and it reached exactly 310. Just did it recently and it stopped at 309.

I’d let it run until it stops on its own. If you have the time.

Both times it went down to 1kw for a very long time and making very little progress.

 

[tjkessler]

Even with an L2 charger the speed of charging tapers off dramatically as you reach a full state of charge.
E.G. yesterday I charged my 3 to 100% for a road trip. For most of the charge time I added range at
22 miles/hr. Once I got to 90% that slowed to 11 miles/hr. When I was within the last 5 miles of charge
the rate slowed down to 4 miles/hr. A supercharger will do the same thing.

 

[Feathermerchan]

The reason it takes so long to complete a 100% charge:
Any time you charge a battery of any chemistry, the cell voltage increases as you apply current and also as the battery stores the charge. With lithium batteries you may not exceed the 100% charge voltage or the batteries will be damages beyond repair. This may include rupturing and burning. The 100% charge voltage is about 4V per cell. Exact maximum cell voltage depends on chemistry and a few other things.. So when you start the charge at a low % of charge (like 50%) the battery voltage is increased but does not reach it's maximum until you reach about 80-90% of charge. Then in order not to exceed the maximum cell voltage the charging system slows down the charge. The closer to 100% charge the slower the charge must be.

What is balancing? It is the Battery Management System (BMS) working to make each cell in the battery pack the same voltage. With 96 cells in series, the BMS operates to keep them the same voltage. Note that this DOES NOT require a full charge, discharge or charging at all.The BMS can operate at any time.

 

[ranss12]

As an update, and as confirmation of posts above - After moving my 3 about 100 yards away from the SC and going to eat lunch, I returned to my car to find that the indicated range had increased from 301 to 306 during my absence - presumably a result of rebalancing.

 

[ecarfan]

As an update, and as confirmation of posts above - After moving my 3 about 100 yards away from the SC and going to eat lunch, I returned to my car to find that the indicated range had increased from 301 to 306 during my absence - presumably a result of rebalancing.

I suspect that your winter temperatures may have reduced your charge rate and the balancing process.

 

[Jedi2155]

100% charge on a supercharger is close to 2 hours from empty. You'll get to 90% in about 1 hr, and the 99% in an an hour 30. The last 1% will probably take 30 minutes or so.

I recommend people charge to 100% from close to empty at least once every few months to keep the cells balanced but try to use it as soon as possible after 100% to avoid unnecessary degradation. Staying at 100% is really bad for the battery.

 

[Feathermerchan]

Jedi - Read my post above. No need to charge for balance. It may help the BMS to determine your actual state of charge but balancing can take place any time.
That is why Tesla says you don't need to charge to 100% except if you need the range.

 

[Jedi2155]

Jedi - Read my post above. No need to charge for balance. It may help the BMS to determine your actual state of charge but balancing can take place any time.
That is why Tesla says you don't need to charge to 100% except if you need the range.

I'm quite aware that balancing can happen at any time, but balancing most often occurs (from my experience) near the top of a charge due to the greater variance in cell voltage there and usually at a low current.