Battery loosing charge?

Faults and Technical chat for the Honda E
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Number5
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Post by Number5 »

I also keep a watch on all the stats, results are never consistant.
The one thing I know is charging from 2% to 100% only consumed 31.48kWh from the supply. I would be surprised if the charging efficiency is greater than 88/89%.

Trykpaa
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Post by Trykpaa »

Number5 wrote: Sat Feb 06, 2021 4:37 pm I also keep a watch on all the stats, results are never consistant.
The one thing I know is charging from 2% to 100% only consumed 31.48kWh from the supply. I would be surprised if the charging efficiency is greater than 88/89%.
I measured charging loss over the first 5000km and got 9%. I get very little variance on this so stopped tracking. ACC to Nextmove charging loss should be 8-13% with Teslas being the abnormal at around 20%.

I occasionally measure range/consumption over a full charge but never get more than - 28,6KWh
Last edited by Trykpaa on Fri Feb 12, 2021 2:44 pm, edited 1 time in total.
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londiniumperson
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Post by londiniumperson »

Number5 wrote: Sat Feb 06, 2021 4:37 pm I also keep a watch on all the stats, results are never consistant.
The one thing I know is charging from 2% to 100% only consumed 31.48kWh from the supply. I would be surprised if the charging efficiency is greater than 88/89%.
The inconsistency is why I removed the outliers from the average & I forgot about the losses in charging.
Take note that the 31kWh is the amount of energy that I'm measuring on the circuit feed before my EVSE which itself uses about 4W (24x7) & then the losses of the cars onboard AC-DC charger.
Assuming total losses of 9.2%:
31kWhx0.9=28.5kWh battery :)
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Trykpaa
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Post by Trykpaa »

keithr wrote: Sat Feb 06, 2021 1:32 pm
[Edit]
Hang on a minute though. (My brains beginning to hurt now!) I presume the car displays miles/kWh based on how many miles it travelled and how many kWhs it started and finished with, i.e. starting and finishing state of charge. Therefore more regen will give a higher miles/kWh figure, but the miles travelled divided by miles/kWh will give the total number of kWh consumed from the battery, not battery consumption and regen combined. Therefore I was right to start with and the difference in available battery capacity is down to the increased battery heat losses at higher speeds. I'm not having a very good day!
More regen will only decrease the consumption because of the free milage contribution. Regen will not roll consumption backward. Simple test, see if you can get a negative consumption figure - not possible.

So energy regenerated should (only reasonable explanation I can find) increase apparent battery capacity.
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keithr
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Post by keithr »

Trykpaa wrote: Sat Feb 06, 2021 8:07 pm More regen will only decrease the consumption because of the free milage contribution. Regen will not roll consumption backward. Simple test, see if you can get a negative consumption figure - not possible.
Or is it? :!: I once drove about 4.6 miles home in my 24kWh Nissan LEAF and ended up with 1% higher state of charge than at the start of the journey. I don't think that car had a display of the individual trip miles/kWh (unless you happened to zero the trip meter at the start), unlike the 40kWh LEAF that I had next, so I didn't get to see what it thought the consumption was. I'd guess that it probably can't display negative values, and it would probably have a maximum value it could display like 99.9 miles/kWh. Perhaps I'll try it one day in the Honda just for fun - reset trip, drive down a long steep hill, then see what it displays as the economy at the bottom of the hill.
So energy regenerated should (only reasonable explanation I can find) increase apparent battery capacity.
Or it improves the energy consumption (like in a hybrid car it improves mpg).

Say the battery starts with 25kWh, you drive 20 miles, regen gives 2 miles extra range, you end up with 20kWh in the battery. Without the regen you would only have travelled (20 - 2) = 18 miles, so that would give 18 / (25 - 20) = 3.6miles/kWh (or in other words, to travel 20 miles without regen it would have used more battery capacity - (20 / 18) * 5 = 5.55kWh). With the regen it will be 20 / (25 -20) = 4miles/kWh.

If you try to calculate battery capacity from miles travelled divided by miles/kWh, then 20/3.6 gives 5.55kWh (although actually you would have only travelled 18 miles so the calculation would have still worked out as 5kWh), whereas with regen 20/4 = 5kWh. Therefore with more regen it could only calculate as the same or a smaller battery capacity, whereas I get the opposite - driving at slower speeds with more regen calculates a larger battery capacity than driving at higher speeds with less regen. The only explanation I can think of is that some battery capacity is used up generating heat in the battery pack, leaving less capacity that can be used by the car - hence the lower usable battery capacity when driving at higher speeds, due to the higher current flow through the battery and heat produced (lost energy) varies by the current squared (H = I(squared)Rt where H is heat, I is current, R is resistance and t is time).
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keithr
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Post by keithr »

My car has been holding charge as normal recently (for a couple of weeks), but now it has once again lost 5% since I last checked it 2 days ago. So turning off the location and vehicle data sharing option, which I turned off 11 days ago, hasn't stopped it losing 3 - 5% every now and again. Puzzling! This time it has been colder weather, but previously it was warmer when it lost charge, so I can't deduce that the cold weather is having an effect.
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keithr
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Post by keithr »

Trykpaa wrote: Sat Feb 06, 2021 8:07 pm More regen will only decrease the consumption because of the free milage contribution. Regen will not roll consumption backward. Simple test, see if you can get a negative consumption figure - not possible.
I couldn't help noticing the display on the VW ID.3 at about 13 seconds into this video. It shows -3kWh/100km as it's being driven (it varies from -1 to -3kWh/100km). So it is possible - even if it is only the instantaneous reading rather than the average over a journey! :)
Trykpaa
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Post by Trykpaa »

keithr wrote: Fri Feb 12, 2021 2:36 pm
Trykpaa wrote: Sat Feb 06, 2021 8:07 pm More regen will only decrease the consumption because of the free milage contribution. Regen will not roll consumption backward. Simple test, see if you can get a negative consumption figure - not possible.
I couldn't help noticing the display on the VW ID.3 at about 13 seconds into this video. It shows -3kWh/100km as it's being driven (it varies from -1 to -3kWh/100km). So it is possible - even if it is only the instantaneous reading rather than the average over a journey! :)
That's a different car. E won't show negative consumption. Try it.

However it does seems as if E is calculating negative consumption so what display shows is different values than what the computer uses.
milligoon
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Post by milligoon »

With the recent cold have the losses increased?
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keithr
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Post by keithr »

milligoon wrote: Fri Feb 12, 2021 8:35 pm With the recent cold have the losses increased?
No, not really. It has lost 3% in one day, and 5% over two days, and 9% over 5 days, but most of the time it doesn't lose any charge, e.g. it has just gone two weeks without any loss. At the start of the recent cold weather it didn't lose any charge. I know because I put the 12V battery on charge and so I checked the battery pack SOC then, and after several very cold days it had not lost any charge, but then three days after charging the 12V battery I went to do my weekly shopping and it had lost 5%. The randomness just makes it more puzzling.

The only thing I can think of is that when I close the drivers door and the window moves up, perhaps it doesn't quite reach the top position but sits there draining some power trying to finish closing the window. For example, on Tuesday when I charged the 12V battery I opened the driver's door to pop the bonnet, then 3 days later it had lost 5% charge and when driving the car it sounded noisier from the window, so I pulled up on the window switch and I think it minutely moved the window up, although it was difficult to be sure.
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