[wtatun]

I’ve seen this in multiple other forums (other EVs), is this a thing on the ID4? Does BMS need to be reset ever (via OBDEleven or other means)? Just wondering….

Here’s a page from the Kia manual that looks like it supports this “notion.”

Thoughts? @VW TECHNICIAN ? Anyone?

 

[branden]

Given that 100% is actually 96%, I don't think this will be needed in normal use.

 

[wtatun]

Given that 100% is actually 96%, I don't think this will be needed in normal use.

I assume there’s also a buffer in Kia EVs.

 

[Don]

Given that 100% is actually 96%, I don't think this will be needed in normal use.

Actually, 77 is 94% of 82, not 96%

Don

 

[Greg V]

Actually, 77 is 94% of 82, not 96%

The buffer is split between the "top" and the "bottom". I'm not sure about the ratios, but if it were split evenly, then your "usable" would be between 3% and 97% (i.e. never discharged below 3% nor charged over 97%). Could be 2%-96%, as branden suggested.

 

[voxel]

The buffer is split between the "top" and the "bottom". I'm not sure about the ratios, but if it were split evenly, then your "usable" would be between 3% and 97% (i.e. never discharged below 3% nor charged over 97%). Could be 2%-96%, as branden suggested.

My opinion is there should be more buffer on the bottom. Once Li-ion cells drop below 3.0v they are close to dead. Anything below 2.5v and cells are damaged. I'd be curious on the SoC when the battery shows 40% charge. Are the cells around 3.7v (nominal li-ion voltage)? At 30% @ 3.6v? At 20% 3.4v? Voltage will fall off a cliff under 3.3v (approx) and I'm sure the BMS will basically stop the car before it does. Leaving Li-ions fully charged isn't great long-term but it's not instant-damage like low voltage.

I'm curious if anybody has experimented with hard accelerating with a low battery (20%). Voltage from Andy/Ross-Tech's charts shows a massive sag when accelerating from 25 to 80mph. I wonder if the ID.4 just stops accelerating or let's the cell voltages drop to 3.3v or lower?

 

[VW TECHNICIAN]

My opinion is there should be more buffer on the bottom. Once Li-ion cells drop below 3.0v they are close to dead. Anything below 2.5v and cells are damaged. I'd be curious on the SoC when the battery shows 40% charge. Are the cells around 3.7v (nominal li-ion voltage)? At 30% @ 3.6v? At 20% 3.4v? Voltage will fall off a cliff under 3.3v (approx) and I'm sure the BMS will basically stop the car before it does. Leaving Li-ions fully charged isn't great long-term but it's not instant-damage like low voltage.

I'm curious if anybody has experimented with hard accelerating with a low battery (20%). Voltage from Andy/Ross-Tech's charts shows a massive sag when accelerating from 25 to 80mph. I wonder if the ID.4 just stops accelerating or let's the cell voltages drop to 3.3v or lower?

How big was sag when Ross-Tech.com did his 100% throttle from 25-80 MPH....and what was his SOC.

 

[VW TECHNICIAN]

And for reference VW battery is measured in SOH Ah.

 

[Don]

Whether it's a larger percentage reserved at the top or the bottom, 77Ah out of a total capacity of 82Ah is still 94% with 6% held in reserve

Don

 

[voxel]

How big was sag when Ross-Tech.com did his 100% throttle from 25-80 MPH....and what was his SOC.

According to his thread... 75% and 68% in his two tests.

80 MPH Efficiency Test - Averaged 2.5 mi/kWh at 58*F -...

Today I tried as scientific as possible of a highway efficiency test. I made sure all four pressures were 42 psi cold, per the sticker in the driver's door. I removed the front plate holder (PA has no front plates) and installed a customized euro plate I've had for years from other cars. On a...

www.vwidtalk.com

The pack voltage plummeted to 347.5v from 374.25v going from 26mph to 80.73mph (peaking at 158 kW that happens in 40mph range)

The problem is the cells dropped to 3.6v (lowest value 3.614 at 76mph) under load. 3.5v is about the point where li-ion cells start seeing damage (minor at first) but of course lithium batteries do not have linear voltage curve and plummet non-linearly. So from the data, I would be concerned about hammering throttle to 100mph with this car (at under 40% SOC) and pushing voltage under 3.5v long-term. The battery IR is limiting the performance.

I wonder if the ID.4 has preventive measures to avoid going below 3.5v/3.4v/3.3v? Like ignoring the accelerator input?

 

[Don]

I would be concerned about hammering throttle to 100mph with this car (at under 40% SOC) and pushing voltage under 3.5v long-term. The battery IR is limiting the performance.

I wonder if the ID.4 has preventive measures to avoid going below 3.5v/3.4v/3.3v? Like ignoring the accelerator input?

Good point. I wonder about that as well. In a way, it's no different than the way some drivers treated their ICE's - You see a guy beating his car to death and a year later you see he has it up for sale, ready to move on and beat up another car and you think, "Man, I would never want to own any car that guy has driven for more than 10 miles . . . ."

There are cars that have been treated well, never abused, and then there are the others. In the future there will be programs for interpreting battery health and generating a report on it which will be key selling points for used EV's - Kinda like a records history of how regularly ICE's were maintained

Don

 

[VW TECHNICIAN]

According to his thread... 75% and 68% in his two tests.

80 MPH Efficiency Test - Averaged 2.5 mi/kWh at 58*F -...

Today I tried as scientific as possible of a highway efficiency test. I made sure all four pressures were 42 psi cold, per the sticker in the driver's door. I removed the front plate holder (PA has no front plates) and installed a customized euro plate I've had for years from other cars. On a...

www.vwidtalk.com

The pack voltage plummeted to 347.5v from 374.25v going from 26mph to 80.73mph (peaking at 158 kW that happens in 40mph range)

The problem is the cells dropped to 3.6v (lowest value 3.614 at 76mph) under load. 3.5v is about the point where li-ion cells start seeing damage (minor at first) but of course lithium batteries do not have linear voltage curve and plummet non-linearly. So from the data, I would be concerned about hammering throttle to 100mph with this car (at under 40% SOC) and pushing voltage under 3.5v long-term. The battery IR is limiting the performance.

I wonder if the ID.4 has preventive measures to avoid going below 3.5v/3.4v/3.3v? Like ignoring the accelerator input?

Using obd2 dongle Bluetooth will have so much delay between sending...receiving and processing that your individual cells voltage will be all over the board.
To measure real world data you will need can bus connection
Regarding cutting power at low SOC or lowest cell in the pack is dependent on chemistry...
So what you have found researching li-ion on the internet is not what you will find on VW battery pack if you do single cell benchmark.
There is also built in algorithms how much current you can pull depending on SOC and temperature.....

 

[voxel]

Using obd2 dongle Bluetooth will have so much delay between sending...receiving and processing that your individual cells voltage will be all over the board.
To measure real world data you will need can bus connection
Regarding cutting power at low SOC or lowest cell in the pack is dependent on chemistry...
So what you have found researching li-ion on the internet is not what you will find on VW battery pack if you do single cell benchmark.
There is also built in algorithms how much current you can pull depending on SOC and temperature.....

Lithium batteries are pretty universal... there are variants like LFP/A123/LiFe (home storage or Tesla Model 3 in China), Li-ion with NMC (almost all EVs) or NCA (Telsa), LiPo (hobby RC or high performance low short burst applications), etc. Some have nominal voltages of 3.3v... some 3.7v, some HV at 3.9v (these are never used in cars). There's no magic to them. They have a minimum cell voltage before damage and they all have the same voltage drop off curve (completely different from NiCd, NiMh, etc. which "different" chemistries - these have linear voltage drops from full to discharged).

As long as all of the data is in sync, I don't care about the delay. I am concerned about the massive voltage sag. It just shows the battery can not sustain more than a ~2C load (82 kWh x 2) which is around the peak 158 kWh it was pushing while accelerating. Putting a battery under load and measuring the voltage drop is how you determine battery IR which determines it's "C-rating"

 

[VW TECHNICIAN]

Lithium batteries are pretty universal... there are variants like LFP/A123/LiFe (home storage or Tesla Model 3 in China), Li-ion with NMC (almost all EVs) or NCA (Telsa), LiPo (hobby RC or high performance low short burst applications), etc. Some have nominal voltages of 3.3v... some 3.7v, some HV at 3.9v (these are never used in cars). There's no magic to them. They have a minimum cell voltage before damage and they all have the same voltage drop off curve (completely different from NiCd, NiMh, etc. which "different" chemistries - these have linear voltage drops from full to discharged).

As long as all of the data is in sync, I don't care about the delay. I am concerned about the massive voltage sag. It just shows the battery can not sustain more than a ~2C load (82 kWh x 2) which is around the peak 158 kWh it was pushing while accelerating. Putting a battery under load and measuring the voltage drop is how you determine battery IR which determines it's "C-rating"

2C rate 164 Kwh is not enough to run AWD.
If this is something you think is true...then AWD would need completely new battery pack .
What type of app and specifically what PID did you use to observe this....I'm very familiar with Tesla EV batteries and what they drop under heavy foot.

 

[voxel]

2C rate 164 Kwh is not enough to run AWD.
If this is something you think is true...then AWD would need completely new battery pack .
What type of app and specifically what PID did you use to observe this....I'm very familiar with Tesla EV batteries and what they drop under heavy foot.

Yeah you are right. My guess of 2C for the battery is far off. In separate forum, the Mach-E was measured to have an IR of 36mOhm (which is very good) and an estimate 4C rating.

The data is from Andy @ Ross-Tech. I only briefly glanced at the peak power and the voltage sag during the hard acceleration. I could compute a loose battery IR and estimate a C-rating from a few sample points...

 

[VW TECHNICIAN]

Yeah you are right. My guess of 2C for the battery is far off. In separate forum, the Mach-E was measured to have an IR of 36mOhm (which is very good) and an estimate 4C rating.

The data is from Andy @ Ross-Tech. I only briefly glanced at the peak power and the voltage sag during the hard acceleration. I could compute a loose battery IR and estimate a C-rating from a few sample points...

VW ID4 has way better design and much lower resistance under heavy current vs Mach-E ( it uses same design like GM Bolt pack).
Sustained high demand over 30 seconds will easily feed 2X times of AWD ID4 demand.
Voltage sag is not the issue....it is more related to heat in the pouch style that is limiting factor....and is well tested to find good balance.
Different types of cooling design could improve this cell design and chemistry to sustain 8C-10C.
But it will require VW IDR cooling system.
Something similar what was used on GM Volt battery pack. But more advanced fluid Dynamic design.

 

[John411iD]

These data points - including cell voltage, BMS SOC and peak power - can be gathered in ID.4 with free Car Scanner Elm Obd2. Delay is only 50-70 ms with 2-3 sensors on screen (I turned on ping and UDS-optimisation).

The exported csv file rounds off cell voltage to 3 decimal places. There's data galore, I am not an excel vizard...

 

[Huey52]

btw: Just got confirmation from our esteemed resident technicians that the 12V battery gets recharged whenever it needs to be, regardless if vehicle is off or not main battery charging. So now we know.