Engineering Explained: Best practices tips to slow down LFP Battery degrading & extend SOH life

[Supratachophobia]

I also went from Mach-E to Rivian.
When you say "bigger" which measurement do you mean? I upgraded the skinny tires with (I had a select 18in and then premium 19in ) wider and 20" and noticed a reduction in efficiency with highway driving.

And wider contact patch would definitely do that in my experience. My Michelin IceX/x tires on the Tesla were always the best performing efficiency of the 3 sets I had. I found out later they were at least half an inch narrower than the other 2 sets.

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[Riv E In]

2 questions:

1. Is it CONFIRMED that Standard + battery is a larger software-locked battery?

2. If so, are those owners able to charge higher (because 100% wouldn’t actually be 100%)? Or run it down lower (because 10% wouldn’t actually be 10%)? Or both? Or neither?

 

[SRO]

And wider contact patch would definitely do that in my experience. My Michelin IceX/x tires on the Tesla were always the best performing efficiency of the 3 sets I had. I found out later they were at least half an inch narrower than the other 2 sets.

Bigger heavier tires have a greater moment of inertia similar to a flywheel. It takes more energy to turn them, but like a flywheel you get most all of that energy back. So probably little net effect.

 

[narmstrong79]

2 questions:

1. Is it CONFIRMED that Standard + battery is a larger software-locked battery?

2. If so, are those owners able to charge higher (because 100% wouldn’t actually be 100%)? Or run it down lower (because 10% wouldn’t actually be 10%)? Or both? Or neither?

Rivian sucks with battery, they make it more confusing than it needs to be

1)Yes standard/standard+ (Gen1) is a software locked Gen 1 large (NMC). Gen 1 had a max (NMC)... Gen 2 standard is LFP. Gen 2 large is missing in action, the current large is really a large+ , a large plus is a software locked max which is basically the same as the Gen 1 Max with newer cells. All with NMC

2) I have a Gen 1 Standard+. Since it's pre-locked with 100% being the same as in unlocked @ 80% charging to 100% is fine.

Personally, People need to stop overthinking battery and long-term battery health. Ultimately you going to see the most degradation in the first couple years regardless of how you treat it. You've got a good warranty of at least 8yrs/100k miles by law on all EVs. Charge to whatever you need or want. Unfortunately, based on this video the LFP isn't as great as previously explained. LFP is just a much cheaper material which is why car companies want to move to it.

 

[Riv E In]

Rivian sucks with battery, they make it more confusing than it needs to be

1)Yes standard/standard+ (Gen1) is a software locked Gen 1 large (NMC). Gen 1 had a max (NMC)... Gen 2 standard is LFP. Gen 2 large is missing in action, the current large is really a large+ , a large plus is a software locked max which is basically the same as the Gen 1 Max with newer cells. All with NMC

2) I have a Gen 1 Standard+. Since it's pre-locked with 100% being the same as in unlocked @ 80% charging to 100% is fine.

Personally, People need to stop overthinking battery and long-term battery health. Ultimately you going to see the most degradation in the first couple years regardless of how you treat it. You've got a good warranty of at least 8yrs/100k miles by law on all EVs. Charge to whatever you need or want. Unfortunately, based on this video the LFP isn't as great as previously explained. LFP is just a much cheaper material which is why car companies want to move to it.

Awesome response. Agree confusing as hell. Thank you.

 

[Eeyore]

tl;dr:

* Gen 1 or "bigger than smallest battery" Gen 2: Set daily limit as low as is reasonable for your driving habits (70% is Rivian's recommendation,) charge to 100% sparingly (only when absolutely needed for a trip, charging to it as close to departure time as possible) plug in and charge (to that daily limit) as often as possible.

* Gen 2 smallest battery: Charge to 100%, but don't charge as often, let it get closer to empty between charges.

* All: Don't let charge drop to 0%
* All: When storing the vehicle for a long period (multiple weeks) set max charge to 50% and leave plugged in, then charge to your normal max (per above) before using again.

Thanks for the summary.
Watching a video to gain knowledge is less effective for me than reading.

 

[narmstrong79]

Awesome response. Agree confusing as hell. Thank you.

The missing real 'large' I believe would be NMC as well since they offered it with the performance add-on. You're likely not getting the performance unlocked with LFP.

If there's space in the max pack housing to make a LFP with larger capacity. I think it would be cool if @Rivian simplified

Non performance - dual motor only
Standard - LFP (commute)270 mile
Large - LFP (adventure) 300mile

Performance models. All software locked max NMC. You can either pay for the range upfront or rent the range as needed.
Standard+ . 300 mile dual motor
Large+ 350 mile dual motor
Max - 410 mile dual, 350-70 tri/quad

I would maybe kill off either the tri or quad

 

[Mathme]

Here's a little real-world experience on one of the oldest batteries out there using our 2010 Tesla Roadster Sport. It has a 56 kWh battery in it and when new it had a an advertised range of about 244 miles (or so what I could find on the internet). This car is only capable of L1 and L2 charging - no such thing as DCFC. It generally gets a charge then when it gets down to 20-30 miles of range it gets charged again. There's basically two charge settings - Normal and Max - and we've typically charged to Normal. This week Normal was giving about 130 miles of range while Max was 141 (we needed it for a longer drive).

So on a battery that was designed to last 10 years that's now 14 years old, it still has about 55% of it's original range (130/244) on Normal and 57% on Max Range. It typically takes 3-4 hours to charge it on our L2 charger.

 

[Yossarian]

Though my hardwired EVSE can charge at a higher rate, I have it set to 40 amps. I also have the upper SOC limit set to 65% for local driving, and recharge once I drop below 30%. I've only charged above that a couple of times when we planned to head to our small cabin in the Poconos, a round trip of just under 200 miles. I'm only a few months into Rivian ownership, so a pretty small sample size, but according to Recurrent, my Gen 1 Large battery, at a 54% average charge level, is doing pretty well:

 

[Supratachophobia]

Here's a little real-world experience on one of the oldest batteries out there using our 2010 Tesla Roadster Sport. It has a 56 kWh battery in it and when new it had a an advertised range of about 244 miles (or so what I could find on the internet). This car is only capable of L1 and L2 charging - no such thing as DCFC. It generally gets a charge then when it gets down to 20-30 miles of range it gets charged again. There's basically two charge settings - Normal and Max - and we've typically charged to Normal. This week Normal was giving about 130 miles of range while Max was 141 (we needed it for a longer drive).

So on a battery that was designed to last 10 years that's now 14 years old, it still has about 55% of it's original range (130/244) on Normal and 57% on Max Range. It typically takes 3-4 hours to charge it on our L2 charger.

Another long term data point:
2016 Model S 90kwh (which was never 90, I digress)
214k miles / 8 years old
BMS reads about 59kwh usable. At EPA consumption for that model of 290 watts/mile, 203 miles of range, down from its day 1 brand new range of 292 (~85kwh, Tesla lies).

On the one hand, that's 30% range loss, but on the other hand, that's only 30%.

All that to say this though. Tesla owners pride themselves on bragging about how little range loss they have according to the number on the dash. I would argue the real data is in the BMS for all EVs, so 99% of us will never know the true capacity losses.

 

[MrMusAddict]

NMC = ABC ("Always Be Charging")
LFP = DEF ("Discharge, Eventually Fill")

 

[mkhuffman]

I also went from Mach-E to Rivian.
When you say "bigger" which measurement do you mean? I upgraded the skinny tires with (I had a select 18in and then premium 19in ) wider and 20" and noticed a reduction in efficiency with highway driving.

The stock tires are 245/45 20 and I replaced them with 255/45 20. I think the increase in efficiency is due to two factors: lower rolling resistance and less rotational resistance.

I don't have a way to verify but the rims are rotating more slowly because the tires are bigger, reducing the aerodynamic loss from the wheel rotating. The biggest factor is probably rolling resistance. I put Hankook Ions on that seem to be a little more slick than the old tires. That's subjective, of course. I can spin the tires more easily now. Which I love to do, BTW.

 

[Dave Cundiff]

What I got out of these videos, in addition to some understanding of crystal behavior:

NMC and LFP: "Keep the State of Charge (SOC) high enough to do the job, but no higher."

NMC and LFP: "Don't discharge enough to drive any single cell to 0%. The manufacturer may or may not have programmed a sufficient buffer to prevent this, but it's hard to be sure."

NMC and LFP: "Speed of charging matters little, but heat (especially sustained heat) is bad."
[I note that charging a Rivian, even Level 2, adds moderate amounts of heat, but discharging (driving) only raises battery heat by a little.]

"NMC likes frequent small charges, and prefers to stay at low SOC indefinitely as long as the SOC is enough to do the job."

"LFP also likes to stay at low SOC, but needs recalibration monthly or so by charging to 100%. Otherwise the SOC display becomes inaccurate, which could be a big problem."

I like @MrMusAddict's formula as a memorable simplification of the above:
NMC = ABC ("Always Be Charging")
LFP = DEF ("Discharge, Eventually Fill")

@narmstrong79 and @CharonPDX also had contributions that helped my understanding.

Great thread! Thanks to all!

 

[mkhuffman]

What I got out of these videos, in addition to some understanding of crystal behavior:

NMC and LFP: "Keep the State of Charge (SOC) high enough to do the job, but no higher."

NMC and LFP: "Don't discharge enough to drive any single cell to 0%. The manufacturer may or may not have programmed a sufficient buffer to prevent this, but it's hard to be sure."

NMC and LFP: "Speed of charging matters little, but heat (especially sustained heat) is bad."
[I note that charging a Rivian, even Level 2, adds moderate amounts of heat, but discharging (driving) only raises battery heat by a little.]

"NMC likes frequent small charges, and prefers to stay at low SOC indefinitely as long as the SOC is enough to do the job."

"LFP also likes to stay at low SOC, but needs recalibration monthly or so by charging to 100%. Otherwise the SOC display becomes inaccurate, which could be a big problem."

I like @MrMusAddict's formula as a memorable simplification of the above:
NMC = ABC ("Always Be Charging")
LFP = DEF ("Discharge, Eventually Fill")

@narmstrong79 and @CharonPDX also had contributions that helped my understanding.

Great thread! Thanks to all!

I agree with everything you posted except one small one: the NMC BMS does need to be calibrated once and a while by charging to 100% for it to accurately track the health and total capacity of the battery. And a long discharge to 10% or so from 100% will help the BMS become more accurate. The procedure is to charge to 100%, drive it down to 10%, and then charge again to 100% to improve BMS accuracy.

Obviously it isn't something you need to do daily or even monthly. I would do it once a quarter or every six months. Personally I naturally do it because I charge to 100% when going out of town, and while I don't usually get it down to 10%, I often get close to 20. That's probably good enough.

 

[newbilization]

So for Gen 2 Max pack, to achieve longer and higher battery performance, I should do daily charge to 70% even though my commute is only 10-20 miles a day... Do I understand it right?

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