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Discussion Starter #1
My understanding is that when level 2 charging, there is usually a 9 - 10% loss.. However, I tried to google it but I can't find any information on losses when DC charging. I understand that for example battery management/cooling on the car will pull some power from the charging current. This is very car specific as different cars have different ways to cool the battery and some have none at all.. However, other than battery cooling, what is the loss when DC charging? I would assume that there is less loss than when AC charging as there is no inverter involved as the charge goes directly into the battery.
Does anyone here have real life numbers on what charging loss you can expect on DC charger?
 

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I don't have any figures, but the answer is mostly likely "it depends". Some DC chargers will use thicker, shorter cables, so less resistance in the cable, while others will be longer, a thinner, with more losses with heat (which is why some come with liquid cooling).
 

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Discussion Starter #3
I don't have any figures, but the answer is mostly likely "it depends". Some DC chargers will use thicker, shorter cables, so less resistance in the cable, while others will be longer, a thinner, with more losses with heat (which is why some come with liquid cooling).
Let's assume a regular 50kw charger that does not have cooled cables...
 

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My understanding is that when level 2 charging, there is usually a 9 - 10% loss.. However, I tried to google it but I can't find any information on losses when DC charging. I understand that for example battery management/cooling on the car will pull some power from the charging current. This is very car specific as different cars have different ways to cool the battery and some have none at all.. However, other than battery cooling, what is the loss when DC charging? I would assume that there is less loss than when AC charging as there is no inverter involved as the charge goes directly into the battery.
Does anyone here have real life numbers on what charging loss you can expect on DC charger?
Are you talking about the conversion losses in the rapid charger, or the battery losses.?
 

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Discussion Starter #5
Are you talking about the conversion losses in the rapid charger, or the battery losses.?
I'm just trying to figure out, if the charger supplies for example 40kwh of total charge, how many kwh did the battery charge increase? 37kwh? 38 kwh?? I know that it's not even close to 40kwh.. I try to figure this out to measure battery degradation. For example, yesterday, I added 40.33 kwh of charge on a 50kw charger.. The AVAILABLE battery size of my Kona Electric is 64kwh. I added 57% of charge. If there was ZERO loss, that would translate to a available battery capacity of 70.75kwh. (40.33 / 57) * 100. So, if you "assume 9% loss", then my available battery capacity is still 64kwh and no degradation in excess of the buffer of about 4kwh has occurred.. However, I don't know if 9% is a reasonable number?? Once I know the estimated loss on a regular 50kw charger, I can get fairly close to estimating remaining battery capacity after degradation.
 

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I'd be assuming that the charging losses, I2R in the connecting cable, are near zero compared to the internal battery resistance and conversion. The DC charger output current measurement uncertainty should not be ignored either.
 

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As you paid for the loss due to heat chemical exchanges etc your vehicle consumption is the units shown on the charger.
If you spill petrol whilst filling a car you would have to pay for it and include it in mpg figures.
Miles per kWh should be based on what you purchased not the inaccurate figures given by the car in my opinion.
 

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Discussion Starter #8
I'd be assuming that the charging losses, I2R in the connecting cable, are near zero compared to the internal battery resistance and conversion. The DC charger output current measurement uncertainty should not be ignored either.
If the loss is close to zero, I'm not sure where the additional charge is going. I doubt that my available battery capacity is much over 64kwh. I know that battery cooling pulls between 1.5 and 2 kwh when it kicks on. On my last charge, battery cooling was on for 3/4 of the charging session.. My average charging speed during those 75% of my charging time pulled probably about 5% of the charging energy for 75% of the charge. Even if I apply that 5% loss to the entire charge session and not just 75%, my available battery capacity would be over 67kwh which would be 3 kwh above factory spec.. I believe that total loss has to be at least 9% as otherwise, my available battery capacity would be bigger than factory spec.
 

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Discussion Starter #9
As you paid for the loss due to heat chemical exchanges etc your vehicle consumption is the units shown on the charger.
If you spill petrol whilst filling a car you would have to pay for it and include it in mpg figures.
Miles per kWh should be based on what you purchased not the inaccurate figures given by the car in my opinion.
I'm not worrying about the loss because my consumption figures. All I'm trying to do is to figure out battery degradation.
I'm not worried about "spilling" energy (losses). I don't pay for over 90% of my charges, so this is not a concern about wasted energy or charging cost..I'm just trying to figure out the best way to determine battery degradation.. I assume that at 33500 miles, my 4kwh buffer on my car has not been used up yet and I still have the full 64kwh available but I would like to have a repeatable way of measuring it so when the time comes that my buffer is used up, I want to know how much my battery has dedgraded.
 

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I'd be assuming that the charging losses, I2R in the connecting cable, are near zero compared to the internal battery resistance and conversion. The DC charger output current measurement uncertainty should not be ignored either.
Another approach to estimating efficiency is to estimate the change in the battery pack temperature, specific heat capacity and mass. This will provide some rough figures for a Leaf but might be hard to judge for a cooled battery like the Niro, Kona etc.
 

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Fill up to 100%

Drive with HVAC off in 80 degree weather until 0%

Note total/average consumption.

Then you’ll know your actual usable capacity. Empirically.
 

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If the loss is close to zero, I'm not sure where the additional charge is going. I doubt that my available battery capacity is much over 64kwh. I know that battery cooling pulls between 1.5 and 2 kwh when it kicks on. On my last charge, battery cooling was on for 3/4 of the charging session.. My average charging speed during those 75% of my charging time pulled probably about 5% of the charging energy for 75% of the charge. Even if I apply that 5% loss to the entire charge session and not just 75%, my available battery capacity would be over 67kwh which would be 3 kwh above factory spec.. I believe that total loss has to be at least 9% as otherwise, my available battery capacity would be bigger than factory spec.
Your battery charging losses will manifest as a temperature change in the pack and what is dumped to air via the liquid cooling system. Get an estimate of these and you will be able to better judge the 9%.
 

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Discussion Starter #13
Another approach to estimating efficiency is to estimate the change in the battery pack temperature, specific heat capacity and mass. This will provide some rough figures for a Leaf but might be hard to judge for a cooled battery like the Niro, Kona etc.
I do have all those numbers.. When battery cooling kicks in, you can immediatly see a 1.5 to 2kwh drop in charge power. Before cooling kicks in, the energy received by the car matches the energy delivered by the charger.. Once battery cooling kicks in, there is a 1.5 - 2 kwh drop in the energy that the battery is receiving.. That's less than 5% loss for most of the charge. Battery Temperature increased from about 95F (35 C) to 100.4F (39C). Towards the end of the charge when the car started drawing less energy, the battery temperature dropped to about 98.6F (38C)
 

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Discussion Starter #14
Fill up to 100%

Drive with HVAC off in 80 degree weather until 0%

Note total/average consumption.

Then you’ll know your actual usable capacity. Empirically.
I'm very cautions with my battery pack.. Low SoC is not good for battery life and the lowest SoC that I have ever had was 9%.. I really don't want to run the pack down to zero or close to zero.. I also rarely charge to 100%, probably less than 10 times per year.. There is s top end buffer on the pack but there is no bottom end buffer, so low SoC is not too good for the battery pack. The only thing bad that I'm doing to my battery is using DC fast charging frequently as I have access to a free 50kw charger, not too far from me..
 

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I'm very cautions with my battery pack.. Low SoC is not good for battery life and the lowest SoC that I have ever had was 9%.. I really don't want to run the pack down to zero or close to zero.. I also rarely charge to 100%, probably less than 10 times per year.. There is s top end buffer on the pack but there is no bottom end buffer, so low SoC is not too good for the battery pack. The only thing bad that I'm doing to my battery is using DC fast charging frequently as I have access to a free 50kw charger, not too far from me..
So if you’re never going to use the extremes of the battery, why are you worried about degradation?
 

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The car charging efficiency is better than 93% at peak charging current. During the charging cycle the efficiency varies and is lower at lower charging currents.
 

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Discussion Starter #17
never going to use the extremes of the battery, why are you worried about degr
I'm worried about degradation as I'm driving a lot of miles per year.. I usually drive 35k to 45k miles per year. I got the Kona 6/28/2019 and added 31k miles in my first year. It would have been a lot more if it wasn't for COVID19.. I'm planning on keeping the Kona in the family indefinitely. I do have a LIFETIME warranty on the battery (available on 2019 Kona Electric in the USA only) which is supposed to kick in if the battery goes bad OR if battery degrades below 70%. However, the latter was just communicated to me orally over the phone when I inquired with Hyundai USA if the LIFETIME warranty covered degradation.. I don't have it on paper, so I don't want to find out. Based on my use, I will be at over 200k miles after only 6 years, so I want to find a reliable way of keeping track of my battery. At 33500+ miles right now, I do not have any noticeable reduction in range.
I hope to get over 400k miles out of the battery before it degrades below 80%.
 

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DC-DC losses are 5% or less assuming the battery cooling/heating systems are off.

AC-DC losses are >=10%, and can be as bad as 25% for early ZOE I believe at low current rates.

Presumably if you have a knackered battery using wall figures becomes less helpful as greater internal battery resistance means more kWh to charge up, masking degradation levels.

Is knowing individual cell voltages at a full balanced charge the most accurate measure?
 

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Based on my use, I will be at over 200k miles after only 6 years, so I want to find a reliable way of keeping track of my battery.
Well, I already told you how to work it out.

Failing that there's a diagnostic app I think, but that will always show 100% SOH.
 

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At charge rates of 1 to 1.5 C (i.e. 50 - 75 kW charger on a 50kW battery) the degradation is minimal, the problem is with higher power chargers 100kW and above. At 2C degradation is significant and above that it’s serious. This of course is based on current battery chemistry which is why very fast charge rates will need different cell chemistry.
 
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