Speak EV - Electric Car Forums banner

1 - 7 of 7 Posts

·
Registered
Joined
·
4 Posts
Discussion Starter #1
Hi,

We own an early 2020 E-Golf. It's a great car and with heat pump have consistently achieved approx 4.1m/kWh (144miles total range) out of it for last 6mths (cold or warm ambient temperatures). Recently though, and suddenly, it only charges to circa 125 miles range, which is proving to be accurate still based on achieving 4.1m/kWh. Haven't changed any settings, driven any differently or excessively used air con etc. This is suggesting to me that only approx 30kWh of the original 35.8kWh battery cells is actually charging now.

Am I missing something? Any suggestions would be gratefully received

Thanks
 

·
Registered
Joined
·
3,987 Posts
Does the car not show you the current average m/kWh? It is more likely that has changed for some unknown reason (dragging brake, damaged alignment, poorly inflated tyres) than the battery capacity has dropped so dramatically as to mean that loss when the e-Golf doesn't initially use all of the capacity available. You have incidentally used the total capacity in your calculation - if you had a range of 144 miles then that would have been consumption of 4.5 m/kWh from the available 32kWh.
 

·
Registered
Joined
·
101 Posts
Maybe some drive up a hill? High motorway speeds? GOM range is a guess based on recent use pattern. Only way to know about battery health is to charge to 100% and then drive down to ~10% to calculate usable battery capacity. GOM is NOT accurate.
 

·
Registered
Joined
·
4 Posts
Discussion Starter #4
Hi,

Thanks for the quick responses, much appreciated. Just to confirm....

For the first 2,800 miles driven in the car over approx last 6mths it has consistently achieved circa. 4.1m/kWh on average, hence charging to GOM estimated range of circa. 144-150 miles each time (35.8kWh battery x 4.1m/kWh anticipated performance). Although never run down to absolute zero range, this is close enough proven over many occasions - i.e. 130 miles use, 14 miles range left etc (we don't charge the car on daily basis). I'm actually surprisingly impressed with accuracy of GOM and vehicle performance consistency, especially over colder initial months, proving potentially the heat pump does it's job too.

Then instantly one day recently it started charging to only circa. 125 miles estimated range. Again, GOM proven over a number of run-downs - i.e. 110 miles use, 15 miles range left etc. Car efficiency remains circa. av. 4.1m/kWh according to vehicle measured data. This continued m/kWh performance is not surprising as journeys remain much the same - settings unchanged, tyres correctly inflated, not just one erratic journey up a big hill etc.

Above therefore suggests that vehicle performance is fine overall but that battery is now acting as a battery with circa. 30kWh capacity, rather than one with 35.8kWh capacity. Would not be surprised if this was the case gradually after say 7yrs. But for this change to happen instantly overnight and remain this way (it's not a one-off situation based on miscalculation of the vehicle electronics) is a bit of a mystery?

Only other alternative is, as you say, that there is some reason why it suddenly isn't actually performing at 4.1m/kWh. But I think it would be too much of a coincidence for (a) sudden loss of performance due to wheel misalignment, calipers sticking etc, to occur as well as (b) vehicle data to be falsely telling me that it is still performing at av. 4.1m/kWh.

Can't come to any logical conclusion other than that I've suddenly lost some of the cells. Before talking to VW, just wandered if anybody else has previously encountered the same.

Thanks again
 

·
Registered
Joined
·
4 Posts
Discussion Starter #5
PS Hadn't appreciated that it doesn't initially use all of the battery capacity available - i.e. that we've potentially actually been achieving 4.5 m/kWh from an available 32kWh. I'm just referencing what GOP says each time, what actual range we have been getting out of it (pretty much the same) and m/kWh performance the vehicle driving data is logging. So it's still a direct comparison between first 6mths and last few weeks. Does that make sense?
 

·
Registered
Joined
·
101 Posts
In my 2017 I found 89% of 35.8 kWh gross was usable (31.9 kWh) when new. The only times I have seen a change in GOM is with either high speed driving or significant ambient temperature swings. Given the posts I have seen about bad cells, I don't think it is a bad cell as the car's BMS would probably not let you drive. In my perusing of the cell voltages (most of the 88 cells, they are all typically within 0.001 volts of each other, so in my car they are very well matched). As I said before, the best way to know is to perform a capacity test, even though your data seems to be pretty close to such a test (to be extra certain about your capacity, try to measure how much energy you put into he car when charging it from ~10% to 100%, to check the car's efficiency measurement). If you bring the car to VW, my guess is the dealer would perform such a test. If indeed you lost 20 miles of range at 4.1 mi/kWh, that is a drop of 5 kWh, and your pack would not meet the warranty threshold of 70% net capacity (25.1 kWh net assuming 35.8 kWh gross when new). I'll keep thinking about this....
 

·
Registered
Joined
·
4 Posts
Discussion Starter #7
That's really useful info, thank-you. I probably confused things a little bit originally by not appreciating lesser usable net capacity vs advertised capacity, and for even mentioning GOM range estimates. In short, actual (fairly well proven) range has dropped instantly from circa 144 miles to circa 125 miles from full battery regardless of initial range estimate. Last couple of charges it's actually been run down to 10 miles range each time as well (am blaming my wife for that!). Will continue to keep an eye on it for another month and try to measure the actual charge too.

Did wonder what the battery warranty actually meant in terms of accepted deterioration but dealerships I spoke to prior to buying it seemed to have average knowledge of what they are selling (which is fair enough) and never got round to properly researching it.

Thanks again
 
1 - 7 of 7 Posts
Top