How to Maximize EV Battery Life

[Lars]

Best charging practices, how to maximize EV battery life.
Source: These slides were ‘snipped’ from a ZOOM meeting held by the EV Society Canada.
(https://evsociety.ca/)

The guest speaker was Dr. Jeff Dahn ( https://www.dal.ca/diff/dahn/people/jeff_dahn.html) one of most knowledgeable people in the world about EV batteries. The images summarize his presentation and will provide a guide how to maximize battery life.

Quick review:
#1 Charging frequently with short DOD (Depth of Discharge) cycles is good. Fewer deep DOD charges are not good.

#2 The makeup of the battery in your car, single crystal positive electrodes and moderate nickel content are the best. Problem: Getting this info very difficult. One would expect the sales people would know the answer but they don’t. The ICE equivalent question would be “and what type of engines can I have this car with? 4 – 6 or 8 cylinders?

#3 For long battery life if one has a Long Range EVs with high nickel content (>75N in NMC) it should be charged only to 75%.

Summary: Since one likely does not know the makeup of the battery, operating the car between 70% and 45% SOC would be ideal.

 

[Genevamech]

Thanks for what feels like a little bit of "insider information!"

So broadly the advice given here and elsewhere is to keep the SoC between 30-80% or so with the understanding that a narrower range is better. It sounds like this person's recommendation, based on their testing, is in line with this advice but narrows the range to 45-75.

It also sounds like the effect is very strongly linked to the specific battery cell construction, which I suppose most of us kinda intuited already but it's good to have some specific idea of what's going on. Do we have any details about the cells used in Hyundai vehicles specifically?

 

[Lars]

Thanks for what feels like a little bit of "insider information!"

So broadly the advice given here and elsewhere is to keep the SoC between 30-80% or so with the understanding that a narrower range is better. It sounds like this person's recommendation, based on their testing, is in line with this advice but narrows the range to 45-75.

It also sounds like the effect is very strongly linked to the specific battery cell construction, which I suppose most of us kinda intuited already but it's good to have some specific idea of what's going on. Do we have any details about the cells used in Hyundai vehicles specifically?

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Yes, essentially we have no idea that we have 4 or a 6 cyl ICE engine.
I am not sure anyone in Hyundai's distribution networks knows the answer. And this lack of information is likely true for most other manufacturers, perhaps with the exception of Tesla.

 

[Ferenc Jakab]

May answer some questions up to 2019.
electricrevs.com/2018/12/20/exclusive-details-on-hyundais-new-battery-thermal-management-design/

 

[Genevamech]

I think the battery-as-engine analogy is deeply flawed. I wasn't going to say anything but if we're going to try to make it a thing...

The number of cylinders an engine has is a basic metric that everyone understands and is somewhat intuitive on a superficial level (more cylinders = more betterer, right?). The specifics of battery chemistry and construction, like how much nickel is in the electrodes, is a nerdy detail that is meaningless to the vast majority of people.

So to fix the analogy: The number of cylinders would be comparable to knowing the voltage and/or kwh rating of the battery pack. The specifics of the battery construction would be like knowing if the connecting rods are cast or forged, or what specific alloy the block is made of; Interesting and maybe relevant to a handful of people, but not something you'd typically sell a vehicle with and honestly shouldn't expect a lowly salesperson to know.

 

[Lars]

May answer some questions up to 2019.
electricrevs.com/2018/12/20/exclusive-details-on-hyundais-new-battery-thermal-management-design/

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Many thanks for digging this up. The article was dated 2018 December and based on the 2019 Kona EV. Since then both Hyundai and us survived a major battery recall. The replacement batteries may or may not use the same battery chemistry. But since there so no later info I propose we assume that the drive batteries in our Kona EVs use NMC 622 (60 percent nickel, 20 percent manganese, and 20 percent cobalt). To put this info in context go up to the top of this post.
Quote from slide 2:
"If the LI-ion battery in your EV uses single crystal positive electrode materials with moderate Ni content (i.e. NMC532, NMC622), then you really do not need to worry about micro cracking in the positive electrode at all. So charge when you like."

Based on this, the battery recall notwithstanding, it looks that Hyundai picked a high performance battery in the Kona. Hence the good range we enjoy. Of course we still not know if the battery uses 'single crystal positive electrode materials'.

Disclaimer: I am not a chemist I am just putting together info morsels.

 

[KiwiME]

I suspect someone who’s an expert in the subject might find it difficult to condense their advise into simple points and still fill out enough time for a lecture.
The manufacturer should be providing this information but the clash might be that they don’t want owners blaming them for running out of charge due to misinterpreting their advice.

 

[Tim94549]

So if I read that right, the suggestion is to just always leave the vehicle plugged in when not driving - setting max charge to 75% ??

I don't drive much - I usually don't have to charge but once a month ... and had been doing so to 90% after dropping to 18-20% .. I've checked my cells using a OBDM Dongle and they continue to top out at 4.16 (volts?). So this is confusing to me ... 2020 Ultimate.

 

[KiwiME]

I don’t drive much either and wait until I drop to under 45% then add 20% overnight to reach about 65%.
So my average SoH is about 55%.
The most I’d need in one day is 10% and that’s what allows this fairly optimal SoC span.

 

[Lars]

So if I read that right, the suggestion is to just always leave the vehicle plugged in when not driving - setting max charge to 75% ??

I don't drive much - I usually don't have to charge but once a month ... and had been doing so to 90% after dropping to 18-20% .. I've checked my cells using a OBDM Dongle and they continue to top out at 4.16 (volts?). So this is confusing to me ... 2020 Ultimate.

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Dr. Dahn mentions that the NMC422 using single crystal positive electrode materials 'eminently suitable for vehicle to grid application where many charge discharge cycles will be applied to the battery while the car is parked.' But keep in mind he speaks as a scientist based on his observations.

I would be careful to apply this statement to our Kona EV literally. One; we are not sure about that the Kona batteries use single crystal positive electrode materials. Two; Kona EVs are do not have the required charge control electronics to support VTG. The current charge controller only allows and manages one way power transfer.

Ultimately it is your call but the info on the slide is not an endorsement for Kona EVs.

 

[Genevamech]

I've checked my cells using a OBDM Dongle and they continue to top out at 4.16 (volts?). So this is confusing to me ... 2020 Ultimate.

Unfortunately you can't gauge battery health using the voltage alone. You should be able to use your dongle to get charge/discharge current and energy and with a little math estimate the pack capacity. There's even a PID called "Battery health" but during my own testing that values went up from 92.5% to 94.6% so who the heck knows what that number is actually based on...

 

[electriceddy]

Unfortunately you can't gauge battery health using the voltage alone. You should be able to use your dongle to get charge/discharge current and energy and with a little math estimate the pack capacity. There's even a PID called "Battery health" but during my own testing that values went up from 92.5% to 94.6% so who the heck knows what that number is actually based on...

Our own in house Kona EV Master guiding light @KiwiME did some in depth research on this very item a while back, very interesting reading.

 

[KiwiME]

For what it's worth I recently described a battery capacity test here, measured while discharging the battery over most of its SoC by driving.

I noticed that this OBD device (that we've talked about before) also specifically offers such a test in much the same way, except it's during charging. The video is worth a watch.

But also the Car Scanner app reads some registers that are currently missing from the Torque Pro PIDs, that is the number of AC and DC charge events and the total AC and DC charge energy amounts.

As more 2019-2023 Kona EVs pass into the 2nd-hand market there's bound to be a lot of interest in these subjects.

 

[electriceddy]

As more 2019-2023 Kona EVs pass into the 2nd-hand market there's bound to be a lot of interest in these subjects.

Good point, an extremely useful application of those OBD2 device/software applications particularly when purchasing any used EV.
Another would of course be to do the homework prior to shopping for one by reviewing comments from previous owners in forums such as this one.

 

[Lars]

Good point, an extremely useful application of those OBD2 device/software applications particularly when purchasing any used EV.
Another would of course be to do the homework prior to shopping for one by reviewing comments from previous owners in forums such as this one.

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Reviewing comments from previous owners is a good idea. But remember happy owners generally stay quiet. In reality we are 'early adopters'. Once EVs go mainstream most interested buyers will either be confused by this stuff of reading voltages etc. Actually some may be scared off EVs by this level of analysis.
Interestingly there is a business opportunity to develop reputable businesses to evaluate used EVs and translate OBD2 test results to common folks. Leave out explaining voltage readings. Based on the age of the battery, the reputation of the make/model offered sale and OBD2 readings the battery either looks good or poor or bad.