[Silverspoon]

I’m sure this has been discussed many times but can anyone explain why my egolf seems to have 34kwh usable battery when it should be nearer to 32kwh.
Here’s my logic - I arrive at rapid charger with 32% battery left and charge to 100% which takes 23.2kwh. So 23.2/0.68 (68% difference) = 34.1kwh usable battery... discuss!!

 

[f1geek]

The rapid charger show the energy it delivered to your car, not the energy put into the battery while the car was charging. There is energy loss during charging from heating charging cables (it is likely the losses in the cable connected to the rapid charger are also included in the indicated number), running the car’s computer, etc. if you had the car turned on during the charge session, HVAC usage consumes energy, etc. A better estimation of usable capacity is to drive from 100% to 10% or lower and use the in car efficiency data to calculate capacity.

 

[Michael_G]

I have the 2016 version with a 24kWh battery. I use exactly the same tactic as "Silverspoon" to monitor the SOH of my battery. Admittedly a bit crude, but if you use this method frequently and keep track of the data, I believe that you can track the State of Health. I have recorded the data on over 100 charges. Typically going from 35% to 80% and the battery health is holding steady at about 22.5 to 23kWh of capacity. This is what I understand the is the "real" capacity of the 24kWh battery.

 

[f1geek]

As time passes and you use the pack, the internal resistance will increase and thus it will take more energy to charge the battery, due to energy dissipation by joule heating. Tracking the energy delivered by the DCFC is not a reliable way to measure state of health. The real initial capacity of the e-Golf 24.2 kWh pack is 89% of the gross, or 21.5 kWh net. At least initially, the real usable capacity will not hold steady, so it seams your method is already showing its weakness.

 

[Silverspoon]

I see f1geek’s point - Teslabjorn‘s battery test is from... ‘fully charged and then driven to below 5% state of charge. Battery capacity can then be calculated with the driven kilometers and average consumption’. He also points out many times that the battery has less capacity when driving at motorway speeds.

 

[Michael_G]

As time passes and you use the pack, the internal resistance will increase and thus it will take more energy to charge the battery, due to energy dissipation by joule heating. Tracking the energy delivered by the DCFC is not a reliable way to measure state of health. The real initial capacity of the e-Golf 24.2 kWh pack is 89% of the gross, or 21.5 kWh net. At least initially, the real usable capacity will not hold steady, so it seams your method is already showing its weakness.

I'm not using a DC fast charge. My vehicle does not have that option. I am using a home installed 240v charging station. I have the car control the amperage to 10a. I get a report from the charge station as to how much energy is "pushed" into the battery. It seems that I could use my own calculated Miles/kWh (not the cars) as another means to monitor battery health.

 

[f1geek]

Again, your home EVSE reports energy delivered to car, not battery. There are still losses due to internal resistance of pack and wiring but when you charge on AC you also have to account for the inefficiency of the on board charger as it converts AC to DC power.

 

[Michael_G]

Again, your home EVSE reports energy delivered to car, not battery. There are still losses due to internal resistance of pack and wiring but when you charge on AC you also have to account for the inefficiency of the on board charger as it converts AC to DC power.

Ok. "pushed" into the car. I would think that as the battery degrades, I would begin to see less miles for the same amount of energy pushed into the car. Could this not be used as a "tell" to determine the health or more accurately "The slow decline in battery life"? I acquired the vehicle with 13,000 miles on it. There is no DCFC feature, so one could possibly assume that the battery was as in as good health as might be possible. I have been tracking miles per kWh since I took possession. Wouldn't it be possible to use this data to monitor battery SOH?

 

[Tooks]

Ok. "pushed" into the car. I would think that as the battery degrades, I would begin to see less miles for the same amount of energy pushed into the car. Could this not be used as a "tell" to determine the health or more accurately "The slow decline in battery life"? I acquired the vehicle with 13,000 miles on it. There is no DCFC feature, so one could possibly assume that the battery was as in as good health as might be possible. I have been tracking miles per kWh since I took possession. Wouldn't it be possible to use this data to monitor battery SOH?

Well, yes, it might give you an indication of any trend in degradation.

But, let’s be honest, it’s a given that batteries will degrade, and what are you going to do about it anyway?

If you start to have concerns about the battery, take it in to the dealer and let them check it?

I don’t think trying to second guess the capacity/health of your battery when its capacity will vary with temperature anyway is particularly helpful is all.

 

[Michael_G]

Well, yes, it might give you an indication of any trend in degradation.

But, let’s be honest, it’s a given that batteries will degrade, and what are you going to do about it anyway?

If you start to have concerns about the battery, take it in to the dealer and let them check it?

I don’t think trying to second guess the capacity/health of your battery when its capacity will vary with temperature anyway is particularly helpful is all.

You're correct. Nothing to be done about. I am just having some fun learning about my new toy.

 

[Silverspoon]

You're correct. Nothing to be done about. I am just having some fun learning about my new toy.

They are such good fun aren’t they!!👍

 

[Snax]

Ive had a lot of fun lately! Yesterday morning 100% charge gave us 140 miles and this morning parked in full sunshine on the drive, 100% was 160 miles. 120 mile trip both ways on the m1 gave us 4.6m/kWh yesterday and today I got 5.7 into central london and back. The traffic levels are pretty much back to pre-lockdown, speeds around town much slower.

its the best car I’ve ever owned, for sure

 

[Michael_G]

Silverspoon, Snax, You must have a much newer model than me. I can only dream of those distances on a charge. That being said. I am having a lot of fun. I truly love the car.👍

 

[Brew]

OBDeleven might be of interest. It's been mentioned on here before on other threads if you want to hunt them down. Basically an OBD plug and app.

Here's what mine output for the 3 occasions I checked the battery. MY2019 e-Golf with 13K miles on the clock.

I'm not sure what the difference is between the two measurements apart from having EM in the title. There's circa 5% difference between the values so maybe it's the non-usable part of the battery.

HV Battery Charge State	High Voltage Battery Energy Information [Wh]	Calculated 100% [kWh]	HV-EM High Voltage Battery Energy Information [Wh]	Calculated 100% [kWh]
67.0%	20600	30.75	19650	29.33
36.0%	10875	30.21	9950	27.64
64.5%	19600	30.39	18650	28.91

 

[Arianto Nugroho]

Yea.. I always wonder what's the different between the 2 values. Odbeleven support is not so helpful.

Anyway, my 2017 has similar values, so I guess I'm still in good shape.

 

[f1geek]

Some data from a trip: ran car from 93% to 7%, based on in car consumption data the car used 23.6 kWh: suggests 27.4 kWh usable. DCFC delivered 24.8 kWh, so there was 1.2kWh lost in the charging process. Assuming 31.8 kWh usable when new, this suggests 14% degradation at 21,000 miles on the odometer. Not great. I thought the pack would hold up better. I will need to perform a 100% to ~5% SoC test to verify this data. I

 

[Eguy]

Some data from a trip: ran car from 93% to 7%, based on in car consumption data the car used 23.6 kWh: suggests 27.4 kWh usable. DCFC delivered 24.8 kWh, so there was 1.2kWh lost in the charging process. Assuming 31.8 kWh usable when new, this suggests 14% degradation at 21,000 miles on the odometer. Not great. I thought the pack would hold up better. I will need to perform a 100% to ~5% SoC test to verify this data. I

I wonder how accurate the consumption data you are seeing is. Did you get this by dividing your actual miles traveled by the stated miles/kwhr or with an app or code reader? Your plan to check it again from 100% down to as low as you can sounds like a good one. You seem to be very tuned in to your car’s behavior and if the pack has degraded by that much I bet you would have noticed the drop in range. I’m interested to hear about your next test results.

 

[f1geek]

I used the car's data visible in the infotainment screen. I don't know how to get more accurate consumption data as I am pretty sure the kWh/100 km data (gives me one more decimal than mi/kWh metric) is the best info available. I don't notice a dramatic drop in range from daily driving but while my daily commute is pretty consistent it is also not unusual that I drive a different route every day to pick up a child, stop by the store, etc. This data was from a 145 mile stint (49 miles down a mountain) and based on taking a similar trip for the past two summers (though the road was repaired this year and I was able to drive faster than in the past two years), I did not expect to have to draft a truck at 55 mph for 15 miles to ensure I made my target of a single DCFC session for the 240 mile trip.