My MX went from 18 miles to 1 miles after parking?

[tslaEbay]

After a long 200 mile stretch I briefly parked my car outside my in-law's home with range showing 18 miles.
The outside temp was in ~50F. After one hour, when I go back to my car it shows the range as 1 mile
After some panic attack I put the car in drive and the range goes to 0 miles
Luckily I was able to put the car into the garage and slow charge for 1 hour and got back home (only few miles away)

Is the cold temp the culprit? The original range estimate was only valid if I continued to drive?
What happend to all the 18 miles? They are gone?

In the past, after 1 hour drive I left my car several times at the range around ~30 miles. It used to hold well.

 

[Les236]

I've had similar. I think this is normal once the charge level gets low. The batteries and the management system probably balanced out and resulted in the lower level. Once I stopped for breakfast at around 6-7% about a mile from the charger, and when I got back in it had dropped to 1%, but was fine getting to the charger.

 

[ATPMSD]

In my ICE car 1/4 tank was always my minimum, in my EV I use 25%. My advice is to avoid the issue.

 

[scottf200]

After a long 200 mile stretch I briefly parked my car outside my in-law's home with range showing 18 miles.
The outside temp was in ~50F. After one hour, when I go back to my car it shows the range as 1 mile
After some panic attack I put the car in drive and the range goes to 0 miles
Luckily I was able to put the car into the garage and slow charge for 1 hour and got back home (only few miles away)

Is the cold temp the culprit? The original range estimate was only valid if I continued to drive?
What happend to all the 18 miles? They are gone?

In the past, after 1 hour drive I left my car several times at the range around ~30 miles. It used to hold well.

Make sure you let your car sit and many different SOC % levels to help in the BMS estimations. HTH

Via: How I Recovered Half of my Battery's Lost Capacity

For the BMS to execute a calibration computation, it needs data. The primary data it needs to to this is what is called the Open Circuit Voltage (OCV) of the battery and each parallel group of cells. The BMS takes these OCV readings whenever it can, and when it has enough of them, it runs a calibration computation. This lets the BMS now estimate capacity vs the battery voltage. If the BMS goes for a long time without running calibration computations, then the BMS's estimate of the battery's capacity can drift away from the battery's actual capacity. The BMS is conservative in its estimates so that people will not run out of battery before the indicator reads 0 miles, so the drift is almost always in the direction of estimated capacity < actual capacity.

So, when does the BMS take OCV readings? To take a set of OCV readings, the main HV contactor must be open, and the voltages inside the pack for every group of parallel cells must stabilize. How long does that take? Well, interestingly enough, the Model 3 takes a lot longer for the voltages to stabilize than the Model S or X. The reason is because of the battery construction. All Tesla batteries have a resistor in parallel with every parallel group of cells. The purpose of these resistors is for pack balancing. When charging to 100%, these resistors allow the low cells in the parallel group to charge more than the high cells in the group, bringing all the cells closer together in terms of their state of charge. However, the drawback to these resistors is that they are the primary cause of vampire drain.

 

[tslaEbay]

Make sure you let your car sit and many different SOC % levels to help in the BMS estimations. HTH

Via: How I Recovered Half of my Battery's Lost Capacity

Thank you @scottf200..I'll try this out.

 

[TJtv]

Similar things happen to me. I posted a similar thread on it last year Battery depletes rapidly when parked at low SOC

No known solution. It keeps happening to this day. Some people say that it's just the changing temperature or battery pack recalibrating but I don't believe it. I think these aged batteries really do have very high self discharge when they're at low SOC. Can't prove it, but that's what it feels like.

 

[tslaEbay]

Similar things happen to me. I posted a similar thread on it last year Battery depletes rapidly when parked at low SOC

No known solution. It keeps happening to this day. Some people say that it's just the changing temperature or battery pack recalibrating but I don't believe it. I think these aged batteries really do have very high self discharge when they're at low SOC. Can't prove it, but that's what it feels like.

Is it because now BMS is thinking it needs to warm up the battery and that requires 8% of energy (18 miles)? or those 18 miles got discharged? If I had continued my drive without stopping I would have got 18 miles? Maybe we never know answer for this.

From now on, I'm not going to take a break when my car shows less than 30 miles range

 

[TJtv]

Is it because now BMS is thinking it needs to warm up the battery and that requires 8% of energy (18 miles)? or those 18 miles got discharged? If I had continued my drive without stopping I would have got 18 miles? Maybe we never know answer for this.

I also don't know the answer. My suspicion is that those 18 miles got discharged. I don't think it has anything to do with the BMS thinking it needs to warm up the battery. One of my trips was on a hot 90F day and had been driven for 2+ hours before being parked at 17miles remaining. The battery should be sufficiently up to temperature in that scenario to not require heating.

 

[tslaEbay]

I also don't know the answer. My suspicion is that those 18 miles got discharged. I don't think it has anything to do with the BMS thinking it needs to warm up the battery. One of my trips was on a hot 90F day and had been driven for 2+ hours before being parked at 17miles remaining. The battery should be sufficiently up to temperature in that scenario to not require heating.

you lost 17 miles in that case too?

 

[fr100]

That's why they put up the message "We recommend charging now" when you're at low SOC. You can't rely on having that same amount of range left when you return to the car later.

 

[TJtv]

The "charge now, your battery is very low" never even came up in my cases. I have an X60D, brand new it had 200 rated miles @ 100 %, now it's ~182 rated miles @100%. Parking the car with 17 miles is still 10% SOC, parking with 34 miles is still 18% SOC. Neither of those is low enough to trigger that warning.

But even so, the charge on the battery depletes very rapidly when parked even in that 10% - 20% SOC window.

 

[Zuikkis]

Is the cold temp the culprit? The original range estimate was only valid if I continued to drive?

It is caused by temperature drop. Cold battery has less energy. Heating it up would require even more energy.
So yeah, if you had continued driving right away, 18 miles would have been correct.. But once stopped, range starts dropping rapidly if it's cold weather.

This seems to be quite normal behaviour in winter time. I don't think there's anything wrong with your car.

I found a temperature vs capacity graph from the internet:

This is for Panasonic NRC18650PD which is not exactly the cell Tesla uses, but probably is close.

 

[tslaEbay]

It is caused by temperature drop. Cold battery has less energy. Heating it up would require even more energy.
So yeah, if you had continued driving right away, 18 miles would have been correct.. But once stopped, range starts dropping rapidly if it's cold weather.

This seems to be quite normal behaviour in winter time. I don't think there's anything wrong with your car.

I found a temperature vs capacity graph from the internet:

View attachment 929888

This is for Panasonic NRC18650PD which is not exactly the cell Tesla uses, but probably is close.

But @TJtv mentioned noticing range drop from 17 miles when the outside temp was ~90F and he was driving for the past 2 hours before taking the break.

 

[Falcon73]

I made some posts about this on a thread I started. More activity here, I see.

From my (very limited) testing, I've found the problem exists at 11% SoC and below, but not at 18% and above. I wonder where the exact cutoff is, but I do know the car didn't go to sleep when it started at 11% parked the other day. It did sleep at 18%.

So, for me, when we do our road trip with our MX this summer, I will be sure to charge it immediately when stopping below 20% SoC.

Also, the 4.0kWh buffer doesn't seem to factor into this at all for some reason.

I need to do more testing, but I don't like getting our MX very low and it's not very efficient to being with.

 

[balefire]

Happens to my car in the cold parked outside with low SOC.
Doesn't happen in my heated garage.

 

[NewbyMaybe]

There's free or nearly free level 2 chargers or destination chargers available in most areas for your situation.