309 mile range with 40 minutes left to charge

[aronth5]

So today for the first time since I've owned my Model 3 (6 months) I did a full charge or almost a full charge.
When I went to unplug the charger my range was at 309 miles with 40 minutes left on the charge. 32amp 14-50 plus. Normally I get 30 miles of change per hour. I started with 245 miles and scheduled a charge to start at 3:30am.
I know there is pretty significant taper but was still somewhat surprised. Any guesses on what my actual full charge would have been if I left it finish? I'm thinking maybe 311-312.​

 

[LargeHamCollider]

Probably 314-315, btw, nice car

 

[MyJoule]

Cells are probably balancing for those last 30-40 min, That's at least the way it works on the Model S

 

[aronth5]

Cells are probably balancing for those last 30-40 min, That's at least the way it works on the Model S

Thanks, sense. Hopefully I would have gotten to 310

 

[dswansonsb]

The best I've ever gotten is 307 miles on a full charge...

 

[Need]

The best I've ever gotten is 307 miles on a full charge...

I have yet to charge it to full since delivery almost a month ago. But it seems my range has increased because I used to charge to 90% @ around 278 or 279. Now my 90% is at 284. Maybe it factors in my normal driving habits. I am at 241 Wh/mile.

 

[mswlogo]

Is it good to full charge now and then for this “balancing”?

 

[Feathermerchan]

Does not matter. The BMS is always monitoring and balancing. Charging to 100% shortens battery life a little. That's why it is not recommended unless driving immediately after.

 

[eprosenx]

Cells are probably balancing for those last 30-40 min, That's at least the way it works on the Model S

That makes a ton of sense. When I first got my car and was picking it up at the delivery center they had it plugged in and it was near 100%, but it said it was going to take some crazy amount of time to get to 100%.

Cell balancing actually makes sense as to why that last bit would take so long. It can't do cell balancing unless you take the car to 100% I presume, but you also are not supposed to take it to 100% often unless you are going to use it soon after, so it is not something I ever see on a day-to-day basis if I am not planning a trip.

 

[Feathermerchan]

Cell balancing means making sure that each cell is at the same voltage. It can be done at any charge level.

Li-Ion cells cannot be charged past a certain cell voltage or cell damage will occur. When at a low state of charge (say 20%) a relatively large charging current can be used without exceeding maximum cell voltage. As charge level rises, cell voltage also rises and charge current must be decreased in order to prevent exceeding the max cell voltage. So the charge rate tapers off until it is almost nothing at 99% charge.

 

[aronth5]

So based on feedback it sounds like if there was still 40 minutes left to go on charging, cell balancing may not have started.

 

[dhrivnak]

So today for the first time since I've owned my Model 3 (6 months) I did a full charge or almost a full charge.
When I went to unplug the charger my range was at 309 miles with 40 minutes left on the charge. 32amp 14-50 plus. Normally I get 30 miles of change per hour. I started with 245 miles and scheduled a charge to start at 3:30am.
I know there is pretty significant taper but was still somewhat surprised. Any guesses on what my actual full charge would have been if I left it finish? I'm thinking maybe 311-312.​

It is not uncommon for the car to show some crazy and wrong charge times. So I bet you would have topped out just over 310 miles in just a few more minutes.

 

[Jedi2155]

Cell balancing normally only occurs ~100% SOC. Its been recommended to balance you pack at least once every few months. So like going to dentist, don't forget to charge to 100% every once a while. Preferably (but not required) at a slower charge rate, so either 120v, or 10A at 240 would be a random guess of mine to try. The vehicle will try adjust its own charge rate to try to do the pack balancing, but doesn't hurt to help it a bit.

 

[Feathermerchan]

Cell balancing normally only occurs ~100% SOC. Its been recommended to balance you pack at least once every few months. So like going to dentist, don't forget to charge to 100% every once a while. Preferably (but not required) at a slower charge rate, so either 120v, or 10A at 240 would be a random guess of mine to try. The vehicle will try adjust its own charge rate to try to do the pack balancing, but doesn't hurt to help it a bit.

Do you have a link that verifies that balancing only occurs at 100%?
Even my model airplane chargers balance from the beginning of the charge.

 

[Darmie]

I have often heard that the Tesla BMS is always balancing the pack. With TM-SPY or Scan my Tesla, I can see movement on the voltage of each pack jumping around. I also remember years past, using a blinky to charge RC lipo when chargers did not have balancing port. That devise was constantly pulling power off of the higher cell. Sometimes it would be so sensitive, that it would pull power from the other cell if it was a 2 cell battery. With this narrow understanding of cell balancing, I would not think a Tesla battery pack is waiting to near full to start it’s balancing act. What takes so long near 100% charge is some cells reaching 4.2volts before others. So, what happens is resistance is used to bleed off power on the higher cells as normal, while power is provided to the full pack to raise voltage on the lower cells.

 

[mswlogo]

So does charging that last 10% become wasteful too?

 

[jdcollins5]

So does charging that last 10% become wasteful too?

It is not wasteful. It just takes longer for the last 5% or so since it is balancing the pack and progressively slower charging currents.

 

[tivoboy]

I've seen this often when charging to full. Only done it about five times since new, don't need all the range often and it's not good for the battery unless needed.

that said, I see often at 308-311, it will say "remaining time" somewhere between 20-40 minutes, and I'm thinking WHAT is going on, is it really going to continue to draw power and charge for that long and what amount of miles could be added. In the end, it usually "stops charging" in about 5-10 minutes with essentially no additional mileage added.

I think it is balancing and also it's probably just gone into some trickle state and using direct power for some sort of battery optimization or conditioning. So, with THAT in mind, I don't yet know if its okay to stop charging at that point, or is it better to "completed"

 

[jgd108]

I've seen this often when charging to full. Only done it about five times since new, don't need all the range often and it's not good for the battery unless needed.

that said, I see often at 308-311, it will say "remaining time" somewhere between 20-40 minutes, and I'm thinking WHAT is going on, is it really going to continue to draw power and charge for that long and what amount of miles could be added. In the end, it usually "stops charging" in about 5-10 minutes with essentially no additional mileage added.

I think it is balancing and also it's probably just gone into some trickle state and using direct power for some sort of battery optimization or conditioning. So, with THAT in mind, I don't yet know if its okay to stop charging at that point, or is it better to "completed"

That. Don't trust the estimate when it's that close to full.
I did a full charge this summer on 110V while at a friends place and got it up to 314 mi!

 

[Feathermerchan]

OK guys. Here is what is going on. Balancing is going on all the time. It is the BMS job to keep the cells at the same voltage.
As you apply charge current to any battery, its voltage rises. Lithium batteries will fail if the cell voltage exceeds about 4.2V
So the charging system MUST start to reduce current when the first cell in the pack reaches 4.2V
When current is reduced, charge rate is reduced so reaching a full charge takes longer. The closer to full charge, the more the charge current (and rate) must be reduced. The last 10% of charge takes a very long time. Yes cell balancing is also going on but that happens all the time. It is the necessary reduction in charge rate that causes the last bit of charge to take so long.