Fully draining then fully charging Lightning to calibrate BMS?

[randomstriker]

I'll be going on a road trip in the fall. In preparation, I'm curious if it is worthwhile/feasible to calibrate the BMS by fully draining and then fully charging the Lightning, in order to get more accurate SoC readings?

In order to do so, I wouldn't drive it until reaching 0%. Rather, I'd drive it down to about 5%, then leave it parked at home with all accessories (AC, etc.) running.

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[mr.Magoo]

I wouldn't recommend taking it all the way down to 0%.

There's a few guides around where youre supposed to drive it to a low SoC 5-10% and then let it sit (turned off) overnight to "settle in" and then charge it back up to 100% to "calibrate" it. (Calibrate is really the wrong term here)

I do something similar once or twice per year, no real scientific reason and I can't tell if it actually makes a difference in SoC and GOM accuracy.

In the end you might get a few more miles of perceived range, but then again, dropping the highway speeds by 5mph will give you a lot more than that, so only you can determine if it's worth doing it or not.

 

[RickLightning]

You never want to take it down to 0% intentionally, no.

https://www.macheforum.com/site/threads/hv-battery-calibration-procedure.23815/

 

[randomstriker]

https://www.macheforum.com/site/threads/hv-battery-calibration-procedure.23815/

Wow this is super helpful, thanks!

 

[EFG]

There is just such a calibration procedure inherent in using LFP battery technologies. This occurs monthly or so with my Tesla Powerwall 3’s which are LFP. The Lightning is a NMC chemistry and a deep discharge is generally not recommended.

So that’s my take on where that Rule of Thumb might be coming from.

 

[Adventureboy]

I wouldn't worry about the full procedure unless you have a concern or your SOH is say 95% or less. It certainly won't hurt to do it, and it should be done when a battery module is replaced. Charging to 100% and letting it sit there for a few hours will balance the pack and get you ready to go. Try to make sure it gets to 100% before you unplug it. It will sit at 99% for a few hours in some cases as it finishes its calibration. This balances all of the cells in each module and balances all of the modules across the pack.

 

[bmwhitetx]

As stated in the linked article, the battery has an intrinsic capacity. Calibration does not increase this capacity - just makes the estimate of capacity more accurate - maybe.

On the contrary, discharging to low rates and charging to 100% frequently is known to decrease capacity sooner. Suggest reading all the posts on here by @MickeyAO.

Will a one-time "calibration" kill your battery - no. But I think if you are anxious about your first road trip (I was), just plan out charging stops and learn to monitor your mi/kWh times SOC and use a buffer. There are so many other variables when driving (wind, speed, temp) such that a slightly better SOC estimate may be way down on the list of helpful things.

EV road trips are tough on type A personalities like you and me.

 

[chl]

As stated in the linked article, the battery has an intrinsic capacity. Calibration does not increase this capacity - just makes the estimate of capacity more accurate - maybe.

On the contrary, discharging to low rates and charging to 100% frequently is known to decrease capacity sooner. Suggest reading all the posts on here by @MickeyAO.

Will a one-time "calibration" kill your battery - no. But I think if you are anxious about your first road trip (I was), just plan out charging stops and learn to monitor your mi/kWh times SOC and use a buffer. There are so many other variables when driving (wind, speed, temp) such that a slightly better SOC estimate may be way down on the list of helpful things.

EV road trips are tough on type A personalities like you and me.

Also, it is one more charge cycle (or close to it) which is:
1) subtracting from the number of charge cycles left in your battery's life time - presumably there is a charging cycle effect on battery longevity and
2) deep discharging is known to reduce battery lifespan.

So to get the purely psychological effect of a boost in reported range (which is STILL going to be just a guess) one would be spending time and effort as well as doing a small amount of harm to your battery's lifespan...so I do not see the point.

OK, flame me now.

 

[Firn]

To add to that, repeated fast charging appears to be the biggest culprit for the battery misreading the percentage, so if you are road tripping you may just end up undoing the BMS estimator calibration anyways.

Take your trip and leave a little buffer on the bottom, beyond that, maybe just charge to 100% and few times a year to further balance the cells (it does this already, just at a slower rate)

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