Possible to drive on empty / zero battery / charge? Any reserves?

[TontoTaycan]

Is there any type of reserve battery once miles left hits zero? Has anyone experienced this and have any info?

I'm not going to run the mileage down as I would an ICE, but it would be useful to know on that very rare occasion.

My BMW's give me at least 1/2 gallon even at "-----" when the tank is empty.

Sponsored

 

[andrewket]

I can’t answer for the Taycan, but having driven Teslas since early 2013 I’ll say this: You’ll find someone with a story across the entire spectrum, from “I was able to drive 15 miles past zero”, to “The car hit zero and died”, to the worst case “The car said I had 15 miles left and I was 3 miles from the charger and the car died.”

The battery management system in all EVs provides an estimate on the amount of energy in the battery pack. It takes a bunch of things into account, notably the voltage across the cells, the temperature of the pack, and here is the tricky part - the historic voltage of the cells when x amount of energy (kWh) has been consumed (in other words, if the pack should have 87kWh usable and the car has used 87kWh since the last charge, this is the “bottom”), and lastly, the historic voltage of the cells when it was last charged to 100% (to determine degredation over time. This is the “top”).

What I’ve told many people over the years (I used to run a Tesla club) is in the summer, you’re likely to get a bit past zero. In the winter, you’re playing Russian roulette when you hit single digits. You can help the BMS calibrate by occasionally charging to 100% and running it down to zero and then back up to 100%. This will make the estimate more accurate; it won’t reverse degradation.

I hope that helps...

 

[TontoTaycan]

It helps a lot. Very informative. Thank you!...

 

[andrewket]

I should add - when the car dies, the battery pack isn’t empty. The BMS won’t allow the cells to be fully discharged. Doing so is very harmful to their longevity.

 

[PanameraFrank]

I've driven 2 miles on 0% and turned it off and back on. FWIW. I would not recommend it.

 

[kort]

I would never depend on going beyond zero, while the meter might be a bit off it could also be spot on and sitting waiting for a tow is no fun

 

[NC_Taycan]

To add one thing to andrewket's excellent response, it is not electrically possible to directly measure the state of charge of Li-Ion cells. I believe it is chemically possible but not practical. Hence all the calculation and estimation pointed out in his answer.

 

[REIL]

I can’t answer for the Taycan, but having driven Teslas since early 2013 I’ll say this: You’ll find someone with a story across the entire spectrum, from “I was able to drive 15 miles past zero”, to “The car hit zero and died”, to the worst case “The car said I had 15 miles left and I was 3 miles from the charger and the car died.”

The battery management system in all EVs provides an estimate on the amount of energy in the battery pack. It takes a bunch of things into account, notably the voltage across the cells, the temperature of the pack, and here is the tricky part - the historic voltage of the cells when x amount of energy (kWh) has been consumed (in other words, if the pack should have 87kWh usable and the car has used 87kWh since the last charge, this is the “bottom”), and lastly, the historic voltage of the cells when it was last charged to 100% (to determine degredation over time. This is the “top”).

What I’ve told many people over the years (I used to run a Tesla club) is in the summer, you’re likely to get a bit past zero. In the winter, you’re playing Russian roulette when you hit single digits. You can help the BMS calibrate by occasionally charging to 100% and running it down to zero and then back up to 100%. This will make the estimate more accurate; it won’t reverse degradation.

I hope that helps...

I did see a video review last fall 2020 where they test drove the car to zero and then used a procedure of turning the car off and instantly back on. This gave them half a block of driving distance.
Additionally, I believe I read about this procedure in the US manual and it is for emergency purposes to allow you to pull off to the side of the road for safety. Cannot find the written procedure yet. Still searching.

 

[andrewket]

I did see a video review last fall 2020 where they test drove the car to zero and then used a procedure of turning the car off and instantly back on. This gave them half a block of driving distance.
Additionally, I believe I read about this procedure in the US manual and it is for emergency purposes to allow you to pull off to the side of the road for safety. Cannot find the written procedure yet. Still searching.

I saw that video too. It was done by the same guy that did the cannonball run.

 

[daveo4EV]

adding to what @andrewket was saying

there is _NO_ way to externally tell if an Lion Battery or "cell" is empty - rather you implement some metering where a computer measures the power in & the power out - by dead reckoning - i.e. it's a "counter" - 100 watts in - 200 watts out - 50 watts in - 75 watts "out"…it's a giant SWAG (Scientific Wild Ass Guess)

so when the car indicates "zero" - first off it's not "true" zero - you can't drain LiON to full/true zero it damages the cells - 2nd off it' the zero Porsche engineering has chosen to "be zero" - and 3rd off it's the zero as determined by the in/out counters on the power in/out measurements…

I think you can drive a Taycan 'beyond' zero - however once you're down in that region of the battery capacity there Is no telling what actual amount of power you have left and even if you could access the internal meassurements/counters - even those are a "guess" and not entirely accurate

I'd recommend avoiding "zero" unless it's the most dire of circumstances.

 

[feye]

Is there any type of reserve battery once miles left hits zero? Has anyone experienced this and have any info?

I'm not going to run the mileage down as I would an ICE, but it would be useful to know on that very rare occasion.

https://www.taycanforum.com/forum/t...n-before-it-goes-into-reserve.2976/post-49395

I only charge my Taycan, when it is empty and I need more range the next day - like my ICE before.

 

[feye]

adding to what @andrewket was saying

there is _NO_ way to externally tell if an Lion Battery or "cell" is empty - rather you implement some metering where a computer measures the power in & the power out - by dead reckoning - i.e. it's a "counter" - 100 watts in - 200 watts out - 50 watts in - 75 watts "out"…it's a giant SWAG (Scientific Wild Ass Guess)

so when the car indicates "zero" - first off it's not "true" zero - you can't drain LiON to full/true zero it damages the cells - 2nd off it' the zero Porsche engineering has chosen to "be zero" - and 3rd off it's the zero as determined by the in/out counters on the power in/out measurements…

I think you can drive a Taycan 'beyond' zero - however once you're down in that region of the battery capacity there Is no telling what actual amount of power you have left and even if you could access the internal meassurements/counters - even those are a "guess" and not entirely accurate

I'd recommend avoiding "zero" unless it's the most dire of circumstances.

I recommend anybody to try out the turtle mode. It gives you a big confidence boost in your Taycan, because you experience how accurate the onboard computer is, and how reliable the range is. Just make sure, you are very near by a reliable charger.

Battery measurements are quite accurate if the right components are used. Age, charge cycles, temperature, voltage, current as well as cell characteristics are used to determine SoC and available energy.

 

[Freakzilla9]

Is there any type of reserve battery once miles left hits zero? Has anyone experienced this and have any info?

I'm not going to run the mileage down as I would an ICE, but it would be useful to know on that very rare occasion.

My BMW's give me at least 1/2 gallon even at "-----" when the tank is empty.

Car wow made a video of few electric vehicles and trying to dry the battery to zero and checking there actual range. A good video which will give u so insight

 

[plumandreal]

Is there any type of reserve battery once miles left hits zero? Has anyone experienced this and have any info?

I'm not going to run the mileage down as I would an ICE, but it would be useful to know on that very rare occasion.

My BMW's give me at least 1/2 gallon even at "-----" when the tank is empty.

I've hit zero and won't do it again!

The car cut out on me! Lucky for me I arrived home just as it hit zero. As I drove through my gates I stopped the car. As soon as the car hit zero mph it refused to budge. (I am glad it wasn't at road junction!!) Eventually, after messing with it and powering it off and on I drove the last few metres to my charger.

But then it refused to charge at any sort of decent rate. It wouldn't accept anything over about 500Ma of charge for about 1.5 hours.

Moral of story. It doesn't have a big useable reserve. The reserve may well be there, but it isn't available to the driver. As I say, I won't do it again!

 

[Roy]

Is there any type of reserve battery once miles left hits zero? Has anyone experienced this and have any info?

I'm not going to run the mileage down as I would an ICE, but it would be useful to know on that very rare occasion.

My BMW's give me at least 1/2 gallon even at "-----" when the tank is empty.

It is possible but a hidden feature.
I was driving in Belgium and the first supercharger on the map did not exist. So I drove to the next. That was there but there was a big high gate and a road between me and the charger. I had 1% left and needed to go to the other of the highway. I had 14 km to drive 23:00h in the evening.
I called my dealer he said. Drive until the car stops. Than push the on/off switch more than 10 seconds. Than you can drive 12 km at the speed of 25km/hr.

This is how i drove on the highway at walkung speed.
At 12 km the car stops.
Then I did the procedure again and drove the last 2 km to the charger.

according to the dealer it is only possible once.In my car it worked twice.
I shut down heaters, airco and all e consumers.
Reached the charger at the last mA...

so yes there is a little spare battery power for emergency.

Sponsored