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Discussion Starter · #1 ·
I was rewatching an interview with the Director of e-mobility VW USA (I believe that is his title). He was explaining that the ID.4 has a higher percentage of useable battery than most EV and usually it is more limited to prevent the battery from going to full charge. The ID4 allows the drive the option of using that extra 20% when the need it. I’m very new to EV ownership so I found this very interesting.

Would you say that is the case with other EV? You charge to full but your useable kw is a smaller percentage of the entire battery capacity?
 

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Yes, maybe wth the exception of some Teslas, I believe. BMW leaves around 5% at the top, more at the bottom. Polestar and Kia leave about 3kWh total unused, i think about 5%. Nissan is around 10% of around 22 kWh.

Of those BMW is the only one who doesn't recommend something other than a full charge, and had no way internally to set a % stop point. The others all allow the user to stop charging before 100%.

The 80% rule seems to be generally accepted but also hotly debated as unnecessary. There's not great evidence either way, yet the manufactures and battery markers make this part of their messaging. I think they're walking a fine line between being practical, and scaring their customers. That's enough to me to generally oblige, yet at the same time doesn't stop me from charging to 100% when I need it.
 

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I was rewatching an interview with the Director of e-mobility VW USA (I believe that is his title). He was explaining that the ID.4 has a higher percentage of useable battery than most EV and usually it is more limited to prevent the battery from going to full charge. The ID4 allows the drive the option of using that extra 20% when the need it. I’m very new to EV ownership so I found this very interesting.

Would you say that is the case with other EV? You charge to full but your useable kw is a smaller percentage of the entire battery capacity?
One reason to reconsider 100% charging: Li ion batteries have been measured to degrade in capacity if charged to 100% and then stored in hot environments for some time. More heat + more time = more degradation.
 

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Discussion Starter · #4 ·
One reason to reconsider 100% charging: Li ion batteries have been measured to degrade in capacity if charged to 100% and then stored in hot environments for some time. More heat + more time = more degradation.
I set mine to 80% and haven’t exceeded that yet, I do have a road trip coming up that I’ll start at 100 but then quick charge a couple times to finish.

I just found it interesting that VW was basically giving the driver the option while he made it sound like past EV’s just limited your max available charge to prevent wear on the batteries.
 

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I just found it interesting that VW was basically giving the driver the option while he made it sound like past EV’s just limited your max available charge to prevent wear on the batteries.
Those are two different things.

The hidden buffer is a failsafe. It provides head room for overruns and balancing. There's also a bottom buffer. I happen to think this one can be more important. Discharge can't be controlled as precisely as charge. Individual cells can discharge faster than their neighbors and risk going negative if the car is being driven down to zero. But the BMS VW is using claims to be able to monitor this to a fine level, and will isolate the pack from the equation if it senses it may be approaching negative territory.

So I find it kind of neato mosquito that the actual kWh of buffer on ID.4's battery is equal in capacity to my i3, which has a battery 1/3 the size.

But the 80% thing is in addition to that hidden capacity, and totally up to the end user whether or not to follow it.
 

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If you keep it generally in 20% to 80% range, which is more than easy in city-only usage - battery will not wear.
 

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If you keep it generally in 20% to 80% range, which is more than easy in city-only usage - battery will not wear.
It will wear but much more slowly. Lithium batteries degrade over time. Narrowing the charge range definitely helps battery life. 20 to 80% is better than 10 to 90%. 40 to 60 % is even better.
 

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It will wear but much more slowly. Lithium batteries degrade over time. Narrowing the charge range definitely helps battery life. 20 to 80% is better than 10 to 90%. 40 to 60 % is even better.
Is there a chart available somewhere on how much better it helps battery life? Is 40-60% twice as good as 20-80%?
 

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Is there a chart available somewhere on how much better it helps battery life? Is 40-60% twice as good as 20-80%?
40-60% is better than 20-80% on the battery, however, the difference is negligible. You just don't want the car to sit at extreme high or low SOC for extended periods of time.
 

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I'm confused. Does ID.4 have a bigger or smaller buffer than most EVs?
So VW recommends charging to 80% of usable capacity to preserve battery life/range? What is their recommendation for discharge -- not to go below 20%, 10%, or what? A salesman told me that it's okay to charge to 100% so long as you start driving after charging, say on a trip that is going to reduce charge below 80%.
So I infer that charging to 100% and then not using the car for a week would be a bad idea. Then how much does Level 1, Level 2, and Level 3 charging factor into this? If a car is charged to 100% at 120v or at 240v is that better for the battery than charging to 100% on a DC fast charger, or not? Keep in mind that charging up to 100% on say 240v as opposed to DC would likely prolong the amount of time that the battery is charging between 80 and 100%.... But my last statement could be wrong as perhaps getting from 80 to 100% would take only a little longer on 240v as it would on DC due to the battery management system tapering off the charge rate?
 

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It's the heat that can kill a battery.

L1, L2, DCFC become irrelevant labels if you only consider the watts being pushed in. The higher the charge rate (kW), the more heat is produced. The higher the level of charge (percent SOC) , internal cell resistance increases, so yet more heat is produced.

Active cooling goes a long was to moderating temperatures, but the battery still gets hot. But the cells at sitting on a cooling tray, not soaking in an ice bath, so cooling can only be so effective.

My impression of the ID.4's buffer is that it's on the slightly smaller side of what's typical, but I haven't seen how much is top end buffet and how much is on the bottom.
 

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I think people are expecting more than we know, and others are overthinking what they should be doing. Right now, from my vantage point, four things are established:
  1. Li-ion batteries degrade less if we do not charge them to 100%, and don't empty them to 0%. That is especially true for leaving a battery at the extreme charge state for an extended period. A generally accepted charge level (and recommended by VW) is 80% for daily use.
  2. DC fast charging degrades a battery more than level 2 or level 1 charging. This is due to both, increased heat and ability to balance out chemical reactions as charge is pushed in.
  3. It is perfectly ok to occasionally charge the battery to 100% as preparation for a long trip.
  4. Batteries with good thermal and charge management (that would include the ID series) degrade less than batteries without (as Nissan Leaf, for example).
Myself, I follow three principles:
  • Always be charging. I come home and plug in, maximum charge set to 80%.
  • Charge to 100% the night before a long trip.
  • DC fast charge only when needed. Although that last one has me worried the least.
Folks who have watched the scene for a while may remember that there is a company here in Southern California that operates limo service with Tesla Xs between LA, Las Vegas, and San Diego. These cars are driven hard, almost exclusively fast charged, and their batteries still last more than 250,000 miles on average. Your ID4 is almost certainly not used as much and as hard, and its battery management compares better to Tesla's than any of the current competition.
 

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One reason to reconsider 100% charging: Li ion batteries have been measured to degrade in capacity if charged to 100% and then stored in hot environments for some time. More heat + more time = more degradation.
Given that they only let you access 77kWh of the 82 available you cant actually charge it to 100% - only about 96%. So I find it odd they still tell you "only to 80%" because that's technically just about 75%. Or am I understanding this wrong? Plus, this is really only relevant to DC fast charging, no? You can Level 1 and Level 2 charge it to "100%" with far less degradation risk.
 

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... there is a company here in Southern California that operates limo service with Tesla Xs between LA, Las Vegas, and San Diego. These cars are driven hard, almost exclusively fast charged, and their batteries still last more than 250,000 miles on average.. .
I would only point out with this example that Tesla builds their batteries using familiar cylindrical cells with cooling fins much like lasagne noodles weaving between each cell. Very different, presumably more effective cooling than our "cold plate" design.


Given that they only let you access 77kWh of the 82 available you cant actually charge it to 100% - only about 96%. So I find it odd they still tell you "only to 80%" because that's technically just about 75%. Or am I understanding this wrong? Plus, this is really only relevant to DC fast charging, no? You can Level 1 and Level 2 charge it to "100%" with far less degradation risk.
There's a head and a bottom buffer, so maybe only 2% at the top and 3% at the bottom. In other words, 100% displayed is probably 98%, and the BMS can't measure this directly while charging, so it needs a little wiggle room or else purposely undercharge.
 

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Given that they only let you access 77kWh of the 82 available you cant actually charge it to 100% - only about 96%. So I find it odd they still tell you "only to 80%" because that's technically just about 75%. Or am I understanding this wrong? Plus, this is really only relevant to DC fast charging, no? You can Level 1 and Level 2 charge it to "100%" with far less degradation risk.
More charge stored for more time in more heat = more degradation
 
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