Periodically charging to 100% for battery health?

[SpeedWagon]

I have heard that it is “healthy” for an EV battery to be periodically charged to 100%. I usually keep mine at 45-65 for daily usage and never really go above 80; is there any benefit to going to 100 once a month etc? I don’t really care about calibrating the range estimate or anything like that, just thinking about max longevity. Searched a bit and didn’t see any discussion on this topic.

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[gtm]

I have heard that it is “healthy” for an EV battery to be periodically charged to 100%. I usually keep mine at 45-65 for daily usage and never really go above 80; is there any benefit to going to 100 once a month etc? I don’t really care about calibrating the range estimate or anything like that, just thinking about max longevity. Searched a bit and didn’t see any discussion on this topic.

Tons of discussion/opinion on the topic but this is some pretty detailed information from a highly reputable source.

 

[SpeedWagon]

Thanks. I will watch the whole thing. From the threads here I have read, and the TLDR I got from this video, I thought takeaway was just to keep around 50% and charge small, frequently (eg 55 start of day, 45 end of day)

 

[gtm]

Thanks. I will watch the whole thing. From the threads here I have read, and the TLDR I got from this video, I thought takeaway was just to keep around 50% and charge small, frequently (eg 55 start of day, 45 end of day)

Keeping the battery charging centered around 50% is what I got from the video as being best practice, but it also shows that it takes a lot of "abuse" to significantly shorten a battery's life. With an 8 year warranty I don't worry too much and charge as necessary but do charge to 60% when I know travel will be local.

 

[j.w.s]

I have heard that it is “healthy” for an EV battery to be periodically charged to 100%. I usually keep mine at 45-65 for daily usage and never really go above 80; is there any benefit to going to 100 once a month etc? I don’t really care about calibrating the range estimate or anything like that, just thinking about max longevity. Searched a bit and didn’t see any discussion on this topic.

While it is very clear that keeping the battery state of charge near the middle of the range will increse lifespan, my view is that occasional charging to 95-100% is "good for" the battery since it gives the battery management system (BMS) an opportunity to balance the cells. Typical BMS implementations only perform balancing near the top of the charge range.

 

[d00d]

Ok, I'll now charge to 60% and return home before 40%, a range of 40 to 54 miles ...not.

 

[SpeedWagon]

While it is very clear that keeping the battery state of charge near the middle of the range will increse lifespan, my view is that occasional charging to 95-100% is "good for" the battery since it gives the battery management system (BMS) an opportunity to balance the cells. Typical BMS implementations only perform balancing near the top of the charge range.

yeah, this is the question i am wondering about - does this periodic full charge actually help health, and how often to do it (as a function of miles or time)?

 

[Tsingtao]

While it is very clear that keeping the battery state of charge near the middle of the range will increse lifespan, my view is that occasional charging to 95-100% is "good for" the battery since it gives the battery management system (BMS) an opportunity to balance the cells. Typical BMS implementations only perform balancing near the top of the charge range.

I would love for one this forum's many engineers to weigh in on the battery cell balancing issue. I just had a porsche rep tell me that I should periodically take my soc down to about 20% and let the battery sit for 4+ hours to allow the BMS to assess each of the cells and then rebalance on the way up. He also told me not to charge up to 80% each night (as that had been my practice since day one with the car) lest the BMS not have a chance to do its thing with cell balancing. Seriously, can't Porsche speak with a single voice and tell us what is best for the battery, cell balancing, etc? (PS I will be very embarrassed if someone points out a section in the owners manual -- which I've never read -- that describes best practices for batteries!)

 

[Tooney]

I would love for one this forum's many engineers to weigh in on the battery cell balancing issue. I just had a porsche rep tell me that I should periodically take my soc down to about 20% and let the battery sit for 4+ hours to allow the BMS to assess each of the cells and then rebalance on the way up. He also told me not to charge up to 80% each night (as that had been my practice since day one with the car) lest the BMS not have a chance to do its thing with cell balancing. Seriously, can't Porsche speak with a single voice and tell us what is best for the battery, cell balancing, etc? (PS I will be very embarrassed if someone points out a section in the owners manual -- which I've never read -- that describes best practices for batteries!)

@Vim Schrotnock got information from a Porsche battery tech (fly-in battery repair 'doctor') about rebalancing process. Link below.
Note this is not the normal, routine charging process outlined in owner's manual.
https://www.taycanforum.com/forum/t...y-replacement-needed.13965/page-6#post-278560

 

[ShiftyWolf]

Tons of discussion/opinion on the topic but this is some pretty detailed information from a highly reputable source.

I took the time to watch this entire video and it was very interesting from a technical standpoint, with science backed advice. I sway toward the theory of doing what I can to protect my battery life within the reasonable limits of my usage. It's not easy for me to take my vehicle down to 15% SOC and back to 100% multiple times over a week or so, but I can very frequently limit my max charge to 75% and stay within a 25% SOC delta when I charge. While this might not be the "perfect" battery protection strategy, the expert discussions seem to say it falls well within the ideal for a battery to far outlast your car.

Slightly off topic but still battery related, I found a TSB that absolutely confirms the battery chemistry change from MY2020 to 2021+. The bulletin also says any 2020 batteries needing replacement will use the newer chemistry batteries.

 

[Sace]

I would love for one this forum's many engineers to weigh in on the battery cell balancing issue. I just had a porsche rep tell me that I should periodically take my soc down to about 20% and let the battery sit for 4+ hours to allow the BMS to assess each of the cells and then rebalance on the way up. He also told me not to charge up to 80% each night (as that had been my practice since day one with the car) lest the BMS not have a chance to do its thing with cell balancing. Seriously, can't Porsche speak with a single voice and tell us what is best for the battery, cell balancing, etc? (PS I will be very embarrassed if someone points out a section in the owners manual -- which I've never read -- that describes best practices for batteries!)

The cell balancing itself is pretty straight forward and done in most multicell batteries. Even hobby R/C cars require balancing the battery packs.

The issue here is that we have no idea of how the BMS is implemented in the Taycan. So it could well be that these "tips" from Porsche is correct.

It sounds like the BMS is simply not well thought out if special steps is required for rebalancing. Maybe people are nicer to their batteries than anticipated in terms of their charging pattern.

 

[d00d]

Watched the video, wondering if the Taycan battery uses single crystal or not, that would have some bearing on how to charge.
Thought is was Kyle Conner that mentioned what the J1.1 battery chemistry is compared to the J1.2, but can't find the reference.
Looks like the 2020 is NMC712 (it changed in 2021);
https://www.batterydesign.net/lg-e66a/

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