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.

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