Charge not starting at specified time. Has anyone had this happen and know how to fix it?

[chl]

Possibly, just to confirm I like to do this periodically, my battery doesn't see extreme charging and discharging events very often, I'm curious from the car scanner data point of view if anything improves with SOH and cell variations. I'm chalking this up to science and personal proof vs. what Ai says.

Got it.

BTW, I was assuming your truck has an NMC and not LFP battery.

With LFPs they do recommend 100% charging periodically (once a week Tesla, or once a month others) for BMS calibration. But with NMCs not required for calibration.

As I understand it, from what I have read, the periodic cycling is to recalibrate the BMS for a more accurate SOC reading and range estimates because LFPs have a flatter voltage curve than NMCs (voltage drop during discharging is smaller for a longer period of time).

If the SOC reading out of calibration, the BMS could over or under charge the battery.

Also, although LFP cells are being balanced during charging (active cell balancing) whether to 80% or 90%, so-called "top balancing" to 100% periodically is 'advantageous'.

Tesla recommends going to 100% at least once a week for their LFP cars. Others say once a month.

However, 100% charging does still take a toll on the battery lifespan of LFPs, although they are said to handle it better, having less of an effect on life span with LFPs than NMCs.

Staying at 100% for long periods of time can be deleterious to battery lifespan of LFPs though.

Apparently unlike NMCs, frequent small charging may be harmful to LFPs. What is meant by 'small' seems to be less than 10%.

See for example: https://www.wiltsonenergy.com/newsinfo11.html

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[TaxmanHog]

My 2022 Lightning has NMC, noted the observations about LFP.

My very slow rate of depletion of the trucks full charge will take time, based on my typical weekly patterns, it might take 3+ weeks to get down to 10%, maybe quicker now that cooler weather is here and more energy will be needed to warm the cabin in the mornings.

 

[chl]

One measurement that I’ve seen improve with a cycle of 100% - 0% is Variation in Capacity Between Battery Modules. When I took delivery of my Flash, with 110 miles on the odometer, the variation was 16.3 Ah. After my first deliberate 100-0% cycle the variation changed to 6 Ah. Next cycle the variation changed to 5.5 Ah. It’s now at 4.5 Ah. It only changes when I go through the full cycle with balancing time at each end. The process I use is to charge to 100% and let it sit at that state for 5-8 hours. Then discharge to as close to 0% as possible and let it sit at that state for 5-8 hours. Then I charge to 100% and go back to daily charging to 80%. I do this quarterly. I’m always close to home when I get to 0%.

Another benefit of doing this is that I know my truck will reliably go to 0% SOC without prematurely shutting down.

Interesting.
We have NMC batteries. With the newer LFPs periodicaally going to 100% is recommended.

I think, if Ford wanted us to do some sort of special charging procedure to balance cells or reduce module differences, e.g., charging to "100%" periodically, I believe they would have put that in the owners manual.

For information about active vs passive cell balancing, see also: https://bacancysystems.com/blog/cell-balancing-and-its-types

One thing to keep in mind is that studies show that the depth of discharge is a significant factor affecting battery longevity due to the chemical processes that go on in the battery during charging and discharging.

I think the bottom line is that if longevity is the goal, shallow charging (no more than 50% of capacity, e.g. 30%-to-80%) is best.

As for the Ah variation among modules, I would have thought the BMS would take care of that on its own if it was a significant issue.

 

[chl]

Interesting.
We have NMC batteries. With the newer LFPs periodicaally going to 100% is recommended.

I think, if Ford wanted us to do some sort of special charging procedure to balance cells or reduce module differences, e.g., charging to "100%" periodically, I believe they would have put that in the owners manual.

For information about active vs passive cell balancing, see also: https://bacancysystems.com/blog/cell-balancing-and-its-types

One thing to keep in mind is that studies show that the depth of discharge is a significant factor affecting battery longevity due to the chemical processes that go on in the battery during charging and discharging.

I think the bottom line is that if longevity is the goal, shallow charging (no more than 50% of capacity, e.g. 30%-to-80%) is best.

As for the Ah variation among modules, I would have thought the BMS would take care of that on its own if it was a significant issue.

BTW, with just 110 miles on your truck (at delivery), the module variations have not had a chance to be evened out by the BMS. Over time the BMS tries to even out module differences, but it does take time. It will do that whether you charge to 100% or not.

There are always slight variations due to manufacturing differences which is unavoidable based on the way the cells are made, the composition of the materials, etc.

Module variations can occur over time as well, due to uneven degrading of the cells, different discharge rates, and imperfect cell balancing.

The BMS does its best to minimize those things, but it is not perfect and it is a time consuming process with all the cells to balance.

Module differences are an issue, but the BMS is designed to minimize them and avoid problems.

The level of difference any BMS can handle is a design factor based on the particular battery parameters, size, etc.

It would be interesting to know what Lightning battery module differences that represent a problem are, but I have not seen that quantified anywhere yet.

EDIT: I have read that charging to 100% will affect the weakest of the modules the most and accelerate their degradation.

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