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Discussion Starter · #1 ·
The Ioniq EV has a battery conditioning system by which the battery can be heated when it is too cold or can be cooled when it is too warm. But how exactly this works is not clear from the manual. The manual suggests that it works when the car is plugged in. But still some questions remain unanswered:


  • In hot weather when the car is not plugged in, is the battery not protected at all?
  • Should you always plug in the car in hot weather?
  • Or does it also work when the battery has enough charge?
  • Is this temperature management for the battery always coupled with charging?
  • For which temperatures does it start to work?
  • So, for which temperatures you better always can plug in the car?
  • When you do so, should you also set it to charge?

Now in several countries temperatures become higher such issues become more relevant. Are there experiences where it was noticed what the battery temperature management system does in warmer weather?
 

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I think you should know first what the temperature is above which the battery is damaged/degraded. I have no idea. Actually I am not planning to plug in the car when I am not charging... The car should be able to handle hot weather.
 

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Discussion Starter · #3 ·
Yes, that's what we hope. But it would still feel better if we can have some understanding to what extent and how the car does this protection.
 

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Discussion Starter · #6 ·
Having the car for more than half a year by now, and after several attempts to get information about how the Battery Conditioning System works, it still remains a mystery. Also dealers do not know it, it seems.
Many of us have experienced periods of hot weather by now; what are our experiences?


  • Who did hear the fan for this system working, and under what conditions was that?

The only cases in which I noticed it, was when charging under high outside temperatures. This does mean it never works when charging has finished or when the car is not plugged in? So, if you charge the car at work in the morning in hot sunny weather and it finishes charging around noon, will the car be unprotected for the rest of the day? It is well-known that it is bad for battery degradation to leave a fully charged battery under high temperatures for a number of hours.
 

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I've noticed the cooling fan (under rear seats) running during charging and in hot weather. But as far as I know there's no comprehensive battery temp. management system like the Bolt or Tesla.

Still better than the current gen Leaf though. They don't even have a fan.

But yeah, don't park your car under the sun for prolonged periods if you can avoid it.
 

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Discussion Starter · #8 ·
As the battery cooling system only seems to work while charging, it is best to use scheduled charging so that the battery is only full just before departure, especially when you have to leave the car in the sun. Or you can charge it up to to say 70 or 80% max by terminating the charging session in time. Or you can do both: set the scheduled charging one or two hours after your departure time.
 
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Discussion Starter · #9 · (Edited)
For those who want to see more background info about battery degradation, see, for example,
,
,
or here.
 

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Or you can charge it up to to say 70 or 80% max by terminating the charging session in time.
Jan, have you done any research into how only charging to 80% might negatively affect the battery?

I have zero experience of how batteries used in EVs are assembled, but I do know that's for some other multi-cell lithium packs where cells are organised in series, each cell has a balance tap which enables the voltage of each individual cell to be balanced to match the voltage of the individual cells of the rest of the pack.
Because charging of lithium-based batteries happens in two distinct phases i.e. the constant current phase followed by the constant voltage phase, balancing of the individual cells occurs only during the constant voltage phase which is toward the end of the charge.
Thus, if the packs aren't not charged to 100% it is possible that this balancing is not completed which will ultimately be detrimental to the pack as a whole.

This (I believe) is primarily the reason why the DC rapid chargers only charge to 80% because the remaining 20% is where all the balancing happens - a function that can only be performed by the on-board charger, which is of course bypassed when using DC.

It follows as a possibility that the BMS dynamically balances the cells when the car is switched off, but if (as an example) you have say three cells in series, two are at 4.2v and one at 3.9v, you would need to apply a load to the higher voltage cells in order to drain them down to 3.9v - not an efficient option that would reduce range.
To balance cells whilst charging, lower currents are usually applied to the entire series pack and individual cells are ’shunted’ to prevent them receiving as much current. This type of balancing can only occur as the SOC climbs toward 100%, as the level of current during the constant current phase is too high for the shunts to cope with.

I would be interested to hear your thoughts.
 

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Discussion Starter · #11 ·
Yes, it is assumed that the real balancing takes place during charging when the 100% charge is approached. For this reason it is advised that still from time to time a 100% charging is done. This is not needed very frequently, but, for example, once a month, preferably just before you have to make a somewhat longer trip. So it is good to charge up to lower percentages most of the time, but not all the time.
 

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Yes, it is assumed that the real balancing takes place during charging when the 100% charge is approached. For this reason it is advised that still from time to time a 100% charging is done. This is not needed very frequently, but, for example, once a month, preferably just before you have to make a somewhat longer trip. So it is good to charge up to lower percentages most of the time, but not all the time.
I have been using Lithium Polymer cells in model aircraft for many years now. In the early days, the advice was the same - balancing was only required periodically. As time went on, the anecdotal evidence began to pile up that resulted in the need to balance every time, such that today all RC chargers are balance chargers. Running a pack through several charge\discharge cycles without balancing not only reduced capacity, but ran the risk of overcharging the cells that had a higher voltage leading to gassing and premature failure.

Of course, there is less risk of a cell being overcharged when only charging to 80%, but I would least think in an EV there would be some better protections in place. I would also posit that the cells used in EV batteries are matched to a much higher tolerance in terms of internal resistance, lessening the chance of an individual cell being significantly out of balance.
 

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so is the lack of the balancing phase the reason charging from rapid chargers reduces battery life?
Personal Opinion: Yes, one of them, because if charged too often without balancing sooner or later a cell will fail. The other of course, is higher charging current increases the heat generated within the cell that ultimately contributes to it's early demise.
 

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Alien and Jan, this is great insight. It leads me to 2 questions as I plan my PHEV acquisition when available in the states:

1 - I've been presuming that a PHEV could be charged off standard USA 120v wall power without a home charger. Albeit much slower than with a charger, but the battery is so much smaller than an EV that this slower rate is acceptable to get it to full charge overnight for example. Is this assumption true?

2 - We've been seeing many HEV owners report that the car never gets the HEV battery up near full charge. Is this in part due to the phenomenon Alien-S is describing where they are intentionally not going beyond 80% while the car is charging the battery, and if so what happens to the longevity of the battery if it never reaches the balancing phase? Similarly, how does this affect what Hyundai may be choosing to do on the PHEV where the car may sometimes be charging the battery and the sometimes it is getting charged by a wall plug or charging unit?

I mention #2 in reference to the PHEV as the battery is small enough that there is a chance the car could get it to a full charge on a very long descent such as coming down from the Colorado mountains where we get 5000 vertical foot or more of descent over long mileage. With the higher capacity of the EV battery I don't imaging many scenarios where the car would conceivably be able to fully charge the battery.

What are your thoughts on these?
 

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Discussion Starter · #17 · (Edited)
For your point 1- in another case it was calculated that 120 V AC wall power provides 1.44 kW power. As the total capacity of the Ioniq PHEV is 9 kWh I believe, it will take about 9/1.44 = 6.25 hours to charge it fully. It may be a bit more if balancing, battery conditioning, preheating/precooling and/or non 100% efficiency is taken into account. So, I would say 7 to 8 hours in general.
 

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Discussion Starter · #18 ·
2 - We've been seeing many HEV owners report that the car never gets the HEV battery up near full charge. Is this in part due to the phenomenon Alien-S is describing where they are intentionally not going beyond 80% while the car is charging the battery, and if so what happens to the longevity of the battery if it never reaches the balancing phase? Similarly, how does this affect what Hyundai may be choosing to do on the PHEV where the car may sometimes be charging the battery and the sometimes it is getting charged by a wall plug or charging unit?
I think the HEV and PHEV use different systems, where the PHEV is handling this like the EV version. I don't know how balancing is handled for the hybrid.

I mention #2 in reference to the PHEV as the battery is small enough that there is a chance the car could get it to a full charge on a very long descent such as coming down from the Colorado mountains where we get 5000 vertical foot or more of descent over long mileage. With the higher capacity of the EV battery I don't imaging many scenarios where the car would conceivably be able to fully charge the battery.
I previously had a first generation Prius PHEV and that was handling the battery charging like the Ioniq EV is doing: last phase before reaching the 100% charge is doing the balancing.
 

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For your point 1- in another case it was calculated that 120 V AC wall power provides 1.44 kW power. As the total capacity of the Ioniq PHEV is 9 kWh I believe, it will take about 9/1.44 = 6.25 hours to charge it fully. It may be a bit more if balancing, battery conditioning, preheating/precooling and/or non 100% efficiency is taken into account. So, I would say 7 to 8 hours in general.
All makes sense. It will also be interesting to see how Hyundai approaches PHEV battery charge levels at the low end. Will they let it get very low or will it be programmed like the HEV to try to keep the battery in the mid-range during driving. I'm guessing more toward the mid-range theory since this is a hybrid and the battery is there to work in conjunction with the ICE. A low battery is not of much help. If that is the case, then a wall charge would often be starting from a nominally mid-range charge, thus only needing 4.5 kW on the long-run average.

One more thing to hear what our early PHEV owners are experiencing.
 

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Discussion Starter · #20 · (Edited)
Then it is important to know whether the 9 kWh capacity is the usable capacity (as for the Ioniq EV, where the 28 kWh is the usable capacity) or total capacity.

In the calculations above I assumed the 9 kWh is usable capacity, but maybe it is not.
 
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