e-Golf battery upgrade: How does an EV know the size of battery it has installed?
Posted: Sun Jun 02, 2024 1:12 pm
Hello - I'm new to this forum - hoping to learn and give back findings from my work.
For me, the VW Golf 7 is the perfect small car. The e-Golf improves on that, save for the relatively short range by modern standards.
I've developed a new obsession with the concept of upgrading the capacity of the e-Golf using new cells.
My initial approach is based on the concept that the e-Golf battery modules break down into PHEV2 form factor cells: 148 x 91 x 26.5 mm
https://pushevs.com/2020/07/03/modern-p ... ery-cells/
This would involve obtaining cells such as these:
https://www.evlithium.com/catl-battery- ... ttery.html
https://meddore.en.made-in-china.com/pr ... oters.html
If we disregard (for the moment!) the physical process of breaking down the pack and modules to get to the cells, replacing with higher capacity cells, reassembling the modules and putting the whole thing back together into the car...
Will the car throw faults now that it has higher capacity cells installed?
Since we have not changed the voltage of any of the cells, how would it even 'know' that the capacity has increased?
Readout from OBD11 shows something knows the capacity somehow - it would have to of course, so it can calculate range based on mi/kWh.
I assume that somewhere in the battery pack, in a BMS or other control module associated with the pack, there is a communication to the car that says 'I am a 35.8 kWh battery pack' and this won't change unless we tell it to: we've performed a 'dumb' swap.
So, in our thought experiment, we now have a car with 58 kWh that 'thinks' it has about 36 kWh.
Does the controller start to figure out over time that the voltage drops more slowly as charge is consumed - so the capacity must be greater?
Does it not, and so any range estimation is thrown off e.g., it reads 120 miles but this drops by 1 for every 1.6 miles driven?
Is it going to get 'confused' when charging and stop when it thinks 36 kWh should be in there, or is it more likely to charge until full 58 kWh by sensing flow of current vs voltage?
The potential for incorrect range readout doesn't bother me so much, but issues with proper charging would naturally be a problem.
VW did upgrade from 24 to 36 kWh with their 2017 facelift from mk 7 to 7.5, so perhaps it is possible to compare the information coming from the battery on both models to see where the capacity figure is stored, whether it can be edited or is on a ROM somewhere.
I get the feeling that, ultimately, I'm just going to have to try it and see in order to answer these questions with any certainty, but I wanted to understand any obvious pre-existing knowledge / pitfalls before jumping down the rabbit-hole (and potentially bricking a car... 'cheap' used e-Golfs are 8 to 10 kGBP as of 2024)
Lots of advice online appears to be 'jUsT bUy a nEw cAr' but I hope this is the right place where the spirit of this type of project and my intent is understood!
For me, the VW Golf 7 is the perfect small car. The e-Golf improves on that, save for the relatively short range by modern standards.
I've developed a new obsession with the concept of upgrading the capacity of the e-Golf using new cells.
My initial approach is based on the concept that the e-Golf battery modules break down into PHEV2 form factor cells: 148 x 91 x 26.5 mm
https://pushevs.com/2020/07/03/modern-p ... ery-cells/
This would involve obtaining cells such as these:
https://www.evlithium.com/catl-battery- ... ttery.html
https://meddore.en.made-in-china.com/pr ... oters.html
If we disregard (for the moment!) the physical process of breaking down the pack and modules to get to the cells, replacing with higher capacity cells, reassembling the modules and putting the whole thing back together into the car...
Will the car throw faults now that it has higher capacity cells installed?
Since we have not changed the voltage of any of the cells, how would it even 'know' that the capacity has increased?
Readout from OBD11 shows something knows the capacity somehow - it would have to of course, so it can calculate range based on mi/kWh.
I assume that somewhere in the battery pack, in a BMS or other control module associated with the pack, there is a communication to the car that says 'I am a 35.8 kWh battery pack' and this won't change unless we tell it to: we've performed a 'dumb' swap.
So, in our thought experiment, we now have a car with 58 kWh that 'thinks' it has about 36 kWh.
Does the controller start to figure out over time that the voltage drops more slowly as charge is consumed - so the capacity must be greater?
Does it not, and so any range estimation is thrown off e.g., it reads 120 miles but this drops by 1 for every 1.6 miles driven?
Is it going to get 'confused' when charging and stop when it thinks 36 kWh should be in there, or is it more likely to charge until full 58 kWh by sensing flow of current vs voltage?
The potential for incorrect range readout doesn't bother me so much, but issues with proper charging would naturally be a problem.
VW did upgrade from 24 to 36 kWh with their 2017 facelift from mk 7 to 7.5, so perhaps it is possible to compare the information coming from the battery on both models to see where the capacity figure is stored, whether it can be edited or is on a ROM somewhere.
I get the feeling that, ultimately, I'm just going to have to try it and see in order to answer these questions with any certainty, but I wanted to understand any obvious pre-existing knowledge / pitfalls before jumping down the rabbit-hole (and potentially bricking a car... 'cheap' used e-Golfs are 8 to 10 kGBP as of 2024)
Lots of advice online appears to be 'jUsT bUy a nEw cAr' but I hope this is the right place where the spirit of this type of project and my intent is understood!