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Leaf 24
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Discussion Starter · #1 ·
This is a question I've been wondering about, yesterday the dashboard stated that I've used up about 50% of the battery and that it would take 7 hours using 3kWh charger to fully charge, however, that doesn't make sense because 7 hours of 3kWh or even 2.3kWh is 21kWh and 16.1kWh, my car is a 24kWh one and half of that is 12kWh so the charge time should be 5 hours and 30 minutes when using a 2.3kWh 3 pin charger. Has anyone here had any experience with this issue?
 

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2021 Hyundai Kona Ultimate 64kWh
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From memory, the 3kW estimate will change depending upon the last charge session you did. So if you last used a 16A Chargepoint it will base it on the 3.3kW max charge speed, or if you last used the granny cable it will give you the time estimate from a 10A charge session.

Remember that it isn't 100% efficient. You will waste some power to things like heat, and add on time, especially when charging at slower rates like you would with a granny cable. Then there is also the extra time where it slows down when nearly full, and the cell balancing process once it is actually full.

It's not perfectly accurate. It is usually a little pessimistic in my experience, but it does give you a decent idea of how long it will take.
 

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Leaf 24
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Discussion Starter · #3 ·
From memory, the 3kW estimate will change depending upon the last charge session you did. So if you last used a 16A Chargepoint it will base it on the 3.3kW max charge speed, or if you last used the granny cable it will give you the time estimate from a 10A charge session.

Remember that it isn't 100% efficient. You will waste some power to things like heat, and add on time, especially when charging at slower rates like you would with a granny cable. Then there is also the extra time where it slows down when nearly full, and the cell balancing process once it is actually full.

It's not perfectly accurate. It is usually a little pessimistic in my experience, but it does give you a decent idea of how long it will take.
I didn't know about the slowed down charging, thanks for pointing that out. The car is always charged overnight using the granny cable, it might be a good idea to do a test once and find out how long it takes to fully charge and then compare that to the charge time that was displayed on the dashboard.
 

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There's multiple factors involved here, some already mentioned:

1) Onboard charger efficiency isn't 100%. For most EV's 80% efficiency is a safe bet. Some may approach 90%. This means it takes more kWh measured at the wall to replenish a given kWh in the battery, increasing charge times compared to a naïve calculation that ignores charger losses.

2) Charging doesn't go at full speed all the way to 100%, it will taper off at the end, however at AC charging speeds it doesn't taper until pretty close to 100%. Even charging at 6kW my leaf charges at full speed to about 95% before slowing, at 2.3kW it would probably charge to around 97% or so before it started to slow down, so this is not a big contributor to charge times.

3) Estimated charge times are rounded to the nearest 30 minutes.

4) The estimated charge time on the dashboard includes about an hours worth of cell balancing. So if it says it will take 5 hours to charge from the current SoC at the currently available charging speed, it really means it will take 4 hours to charge and then it will let the battery balance for an hour before finally switching off. If you go out to the car and check the state of charge an hour before the predicted end time you'll find it's probably sitting at 98% already and drawing almost no power from the wall, once it switches off the SoC figure will jump from 98% to 100%. (It never seems to report 99%)
 
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