Vampire Drain 0.2%/day.... Essentially Zero?

[mkhuffman]

I'm with you on this one. As I was reading the original post, I was thinking to myself, OMFG. About the 2 worst things you could do to a max pack. Icing on the cake would be if it was hot in the garage to top it off. Probably just did more wear on that battery than I did on my Teslas in 3 years. How you use the battery the first year really seems to set the tone for the outlying years as well from what I've seen.

They didn't need to top off to check vampire drain anyway. Just invest in something like Electrafi.

I am still sort of stunned. Almost an entire month at max charge level. I would have been praying for vampire drain to bring my charge level down and running my AC/heat to do it.

This isn't a great analogy, but it sort of makes the point. Keeping your battery at 100% or close to it, is like revving your ICE motor to redline and keeping it there. No imagine your ICE motor kept at redline for a month...

There is almost nothing that could have been done to degrade that battery pack faster than maybe doing the same and parking it in the desert, so there were very high temps to go along with it. Maybe if the garage was very cool, it might have limited the damage.

Here is an easy read that will help others who want to minimize degradation.
https://batteryuniversity.com/article/bu-808-how-to-prolong-lithium-based-batteries

I agree that I would never leave the battery at 100% for a week, even for science. I have my phone limited to 80% when charging to improve battery life.

But I doubt what he did is as bad as you think. In the long run, it was a blip over the life of the battery. If he did it regularly, it might have a measurable impact on the life. Maybe.

So many people don't care and charge their BEVs to 100% every time they charge. When they check their battery State of Health, they report numbers that are better than others who have babied their batteries. IDK why, because I agree with you that the time at 100% should be minimized and only at that level when necessary.

BTW, the OP follows best practices and keeps his battery between 30-70% normally. His HVB is likely in very good shape, even after spending a week at near 100%.

Sponsored

 

[mkhuffman]

Primary reasons:
From what I’ve read and been told by RIVIAN, it is recommended to do a full charge periodically. I hadn’t done one since the beginning of Feb. This calibrates the battery ECU and balances the multi cell battery packs.

Secondary Reason:
Gave me a reason to run some experiments, primarily Phantom drain.

99% of the time my vehicle sits between 30%-70%, lithium -ion battery sweet spot. But similar to my other lithium ion battery operated devices, I do a full discharge and charge periodically.

From what I understand, calibrating the BMS with a full charge every month or two is a good practice, but you don't need to go down to 1%. Starting at 10% is enough, and it avoids the extras stress of a very low charge on the pack. 10% to 100% will calibrate the BMS.

 

[DayTripping]

I agree that I would never leave the battery at 100% for a week, even for science. I have my phone limited to 80% when charging to improve battery life.

But I doubt what he did is as bad as you think. In the long run, it was a blip over the life of the battery. If he did it regularly, it might have a measurable impact on the life. Maybe.

So many people don't care and charge their BEVs to 100% every time they charge. When they check their battery State of Health, they report numbers that are better than others who have babied their batteries. IDK why, because I agree with you that the time at 100% should be minimized and only at that level when necessary.

BTW, the OP follows best practices and keeps his battery between 30-70% normally. His HVB is likely in very good shape, even after spending a week at near 100%.

it wasn’t for a week, it was for almost a month if I read it correctly. I believe it was from May 2 to May 28. That is a pretty long time to keep it at a continuously high state of charge. it would be more like at max state of charge not just high. If it were only a week, I probably wouldn't have said anything.

It you took all my Teslas and my Rivian, and if you added all the time they spent at 100% state of charge it likely would be less 5 hours. On the maybe 10 times, across all the vehicles (6) that I hit 100% SoC, it was unplug and go immediately.

As for some people not seeing as much degradation as you'd expect given bad charging habits, how often will anyone post that they screwed up later? Not to mention some people get lucky. One of my cousins smoked their entire life and never go long cancer. Their sister did. Maybe they live in a cold, or cooler climate, where it is less impactful. My plan is not based on prayer and hope to minimize degradation.

I had a Tesla where I followed their recommendations of daily charging to 70 or 80%. That battery degraded much faster than the ones where I keep my resting charge at 50% and charge just before I leave. I almost never go below 20% and rarely above 70% and when I do, I time it so I immediately unplug and go. My 2 Teslas that are over 3 years old, and in a hot climate, are at 3% degradation or less.

My Y, where I followed the herd approach of charging to 70 or 80% daily (even if I might only drive enough to use just 10% charge or less), degraded over 7% in the first year, in the same climate. I can tell you which approach I am following with my Rivian; resting charge at 50% charge higher if needed, and just before leaving, leave it plugged in all the time and almost never below 20%. One time I went to 16% and in the almost 10k miles I've driven it since buying.

Sponsored