How much further can you Drive your GT when your range says 0 miles?

[RyanRA]

Edit: Sorry folks -- this was previously posted: (https://www.macheforum.com/site/threads/mustang-mach-e-gt-range-test.17994/)

Here’s one test.

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[Mach1E]

Here’s one test.

Soo…….

Does he ever say how far it went? I only heard “quite a few miles.”

That doesn’t really help to do a test and hide the results.

I wonder if roadside charges you if you TRY to get towed on purpose.

 

[generaltso]

Looks to be the same video that was posted when it came out 5 months ago.

https://www.macheforum.com/site/threads/mustang-mach-e-gt-range-test.17994/

 

[RyanRA]

Looks to be the same video that was posted when it came out 5 months ago.

https://www.macheforum.com/site/threads/mustang-mach-e-gt-range-test.17994/

Duh... yup same one. New to the forum (that's my excuse : ) )

 

[RyanRA]

Soo…….

Does he ever say how far it went? I only heard “quite a few miles.”

That doesn’t really help to do a test and hide the results.

I wonder if roadside charges you if you TRY to get towed on purpose.

"10 miles past 0%"

 

[generaltso]

"10 miles past 0%"

Not sure that's even accurate anymore since Ford supposedly added 3 kWh of usable capacity below zero to 2021 ER batteries since then (2 kWh to SR batteries).

 

[phil]

Not sure that's even accurate anymore since Ford supposedly added 3 kWh of usable capacity below zero to 2021 ER batteries since then (2 kWh to SR batteries).

Turns out the additional usable capacity is actually above zero. See discussion here:

https://www.macheforum.com/site/threads/operating-at-lsc-low-state-of-charge.22810/post-534479

 

[dtbaker61]

Edit: Sorry folks -- this was previously posted: (https://www.macheforum.com/site/threads/mustang-mach-e-gt-range-test.17994/)

Here’s one test.

don't try this on your car folks..... hard on the battery

 

[AllenXS]

Brings a new meaning to going flat out?

 

[Vulnox]

It's also important to note that amount below 0 will vary from car to car. The car does not precisely what the actual usable kWh in the battery is at any given time. It can measure consumption and how much is put in, but the battery level is determined by the BMS and it uses current in and current out to determine battery level. There isn't a way to really "measure" to extreme precision the actual charge. Some items like measuring voltage of the cells give a good indicator though.

The point of all that is to say, for those that charge to 80% daily and then drive to work get home at 71% then charge to 80% again, the actual "bottom" of the battery can get further and further away from the BMS. Due to normal battery degradation and losses due to other factors, the BMS can assume there are 4-5kWh less charge in the battery than there really is.

It's why you should from time to time run the battery down to a low level, the lower the better within your comfort level, then charge it back up. It gives the BMS a better idea of where the "bottom" of the pack is.

This only really matters if you are super concerned with the accuracy of the percent of charge shown in the car. But all that is to say, this reviewer may have gone 10 miles past 0, but you may go 20 before the car dies in the same conditions. All depends where the BMS thinks 0 is and it's not going to be the same across all cars. Where for two identical ICE vehicles with the same engines and gas tank sizes and that could expect almost exactly the same mileage below "0" or Empty if all other things are equal.

 

[RyanRA]

don't try this on your car folks..... hard on the battery

I wonder if someone on the forum ended up with that MachE.

 

[dtbaker61]

The point of all that is to say, for those that charge to 80% daily and then drive to work get home at 71% then charge to 80% again, the actual "bottom" of the battery can get further and further away from the BMS.

I don't think this is the way the BMS works.

Most BMS systems 'reset' the ah counter at 100% charge, and have a 'top balancing' design that gets all cells up to the same end of charge voltage. This is why you occasionally want to charge to 100%, not 0%.

The BMS tracks energy consumed by watching current and voltage.... and displays approximate state of charge based on counting amount of energy expended versus theoretical 'full'. The voltage is very flat 'in the middle' with Lithium, so watching amp-hr and voltage to calculate kWhr expended is the only way to even have a clue when voltage is somewhere in the middle.

Then, as the pack nears 'empty', in the last 15% or so, the pack voltage DOES start dropping fairly rapidly, and the BMS systems are usually designed to start throwing warnings at that point because if ONE cell empties before the others, and you are still driving, it will kill that cell forever. Towards the very bottom, whatever voltage sensor hits 'bottom voltage' first shuts the whole thing down. If every single cell has a sensor, you'd be safe. But, usually the sensors are on the smallest parallel strings inside the pack, and if ONE of the cells has less capacity than others, it dies and you lose that capacity forever.

THIS is why it is *really bad* to drive an EV 'until it stops'.

 

[Vulnox]

I don't think this is the way the BMS works.

Most BMS systems 'reset' the ah counter at 100% charge, and have a 'top balancing' design that gets all cells up to the same end of charge voltage. This is why you occasionally want to charge to 100%, not 0%.

The BMS tracks energy consumed by watching current and voltage.... and displays approximate state of charge based on counting amount of energy expended versus theoretical 'full'. The voltage is very flat 'in the middle' with Lithium, so watching amp-hr and voltage to calculate kWhr expended is the only way to even have a clue when voltage is somewhere in the middle.

Then, as the pack nears 'empty', in the last 15% or so, the pack voltage DOES start dropping fairly rapidly, and the BMS systems are usually designed to start throwing warnings at that point because if ONE cell empties before the others, and you are still driving, it will kill that cell forever. Towards the very bottom, whatever voltage sensor hits 'bottom voltage' first shuts the whole thing down. If every single cell has a sensor, you'd be safe. But, usually the sensors are on the smallest parallel strings inside the pack, and if ONE of the cells has less capacity than others, it dies and you lose that capacity forever.

THIS is why it is *really bad* to drive an EV 'until it stops'.

Yeah, the BMS does top balancing, but it doesn't change that it top balances based on voltage and the percentage on the screen doesn't know what the bottom is exactly, how could it?

You are describing balancing when talking about going to 100% and letting the BMS top balance, I am describing calibration. The BMS is involved in both, but what I said is accurate.

https://tesla-info.com/guide/tesla-bms-calibration.php

That is for Tesla, but the idea is the same since EVs are EVs. It describes balancing vs calibration. You need both ends to calibrate, you need one end to balance.

I didn't see anything you said that is counter to what I said. I agree I wouldn't drive my car to 0 either if it can be avoided. The BMS should cell balance even at lower voltages though so a single cell being killed off should be a rare event.

 

[Logal727]

seems like a real genius

 

[RetiredDP]

Soo…….

Does he ever say how far it went? I only heard “quite a few miles.”

That doesn’t really help to do a test and hide the results.

I wonder if roadside charges you if you TRY to get towed on purpose.

I went 20 miles past zero in my GTPE, running 245/45R20 XL CrossClimate 2's. Heated steering mode and heated seats shut off at about the 30-miles-to-zero point, and it went into turtle mode 3 miles before I got home. I was still driving at the -20 miles point! It took 10 hours and 38 minutes to recharge back to 100%, on a 40-amp charger.

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