How low (SOC) CAN you go?

Zprime29 · Thursday at 3:15 PM

WaterboyNorCal said:
Hmmmm. That’s interesting- seems like if that’s the case, then there’s something uniquely flawed about the Lightning NMC packs. I’m not questioning MickeyAO’s lab findings (I remember him and he’s clearly very knowledgeable), but if there was something that happened below 20% SOC that was going to damage the pack, I would think that Ford would be aware of it and get in front of what would end up being a huge problem and likely a class action lawsuit.

That being said, I think we can all agree that for daily driving purposes, keeping the battery pack between 20 and 80% is best.

Mickey warned us that it was one of the 3 worst things that degrades the battery, but we didn't really get a clear indication as to the extent of the degradation. Since I live in the desert and have had 110F or higher for 3 summers now (which was also one of the no-no's) and still have 97% of stated capacity I also think we'll be fine in the long run. I do what I can to help prevent the extreme's (temp and Soc) but I don't worry about it when it's unavoidable.

And for those wondering, I'm basing my degradation on a 14% to 100% charge cycle at 80F and the resulting max kWh available.

PreservedSwine · Friday at 3:54 AM

WaterboyNorCal said:
I don’t think anyone says “never go below 30”. I agree that it’s BETTER for the longevity of the battery pack to stay as close to 50% SOC as possible, but you also have to drive the vehicle.
My battery has very little, if any degradation at 43k miles and I have been below 30% at least 30-40 times on road trips. As I understand it, going below 20% is totally fine as long as you don’t get down near zero and let it sit for an extended period. I have heard about the “I only charge to 50% because I want my battery to last forever” types, which I simply don’t understand. Calendar aging/degradation will happen regardless, and heat-related degradation will also have an effect if you live in a warm environment. I didn’t buy a $55k truck to only use 50% of the battery pack, but that’s just my opinion.

I recall MickeyAO saying he doesn't go below 30.
I'm no expert, but I'm able to recognize one when I see one.
https://www.f150lightningforum.com/forum/threads/running-the-battery-to-0.18974/post-382238

ctuan13 · Friday at 4:26 AM

"Can" and "should" are two very different things. Just look up @MickeyAO 's post history to see his expert insight on the particular cells in Lightning packs. In simple terms, they don't do well with deep cycling and large SOC deltas.

Sometimes this is unavoidable, hell I've had my own incident where I quite literally died on the side of the highway in South Dakota last summer. But in general my practice is to never allow the battery to drop below 40% and never let it charge above 85-90%. In addition, I tend to keep it charged between 55-80% when at home.

I would recommend against deep cycling unless absolutely necessary. Even this summer On my cross country road trip, from PA to WA, I was able to keep my battery percentage above 40% between chargers more than 95% of the time. It may have been a bit slower, but it put less stress on the battery than deep cycling and even longer high C-rate DC fast charging.

WaterboyNorCal · Friday at 9:27 AM

PJnc284 said:
Doesn't look like he's been around lately since trading the lightning for a Kia EV9, but @MickeyAO is probably the only one here who has actually tested the cells from the Lightning pack and didn't let his drop below 20% due to not liking the behavior in the lab below that. Something about the resistance or something but way above my paygrade. Lab behavior doesn't always dictate behavior in the real world as we've seen with how EV batteries have been holding up but his results should be noted.

absolutely agree with you on all points. I try to stay in the 40-85% range for daily driving, which is most of the time. And yes, lab testing tends to be highly repetitive cycling over a very short period of time, and real-world use cases have shown to be less stressful for modern liquid-cooled EV battery packs than lab testing would suggest. I think MickeyAO is waaaaaay more knowledgeable about EV batteries than most of us, and I also think that he would agree that being responsible about charging is one thing, but being obsessive over trying to maintain the perfect SOC to minimize degradation also has diminishing benefits, especially since calendar aging cannot yet be avoided.

WaterboyNorCal · Friday at 9:33 AM

ctuan13 said:
"Can" and "should" are two very different things. Just look up @MickeyAO 's post history to see his expert insight on the particular cells in Lightning packs. In simple terms, they don't do well with deep cycling and large SOC deltas.

Sometimes this is unavoidable, hell I've had my own incident where I quite literally died on the side of the highway in South Dakota last summer. But in general my practice is to never allow the battery to drop below 40% and never let it charge above 85-90%. In addition, I tend to keep it charged between 55-80% when at home.

I would recommend against deep cycling unless absolutely necessary. Even this summer On my cross country road trip, from PA to WA, I was able to keep my battery percentage above 40% between chargers more than 95% of the time. It may have been a bit slower, but it put less stress on the battery than deep cycling and even longer high C-rate DC fast charging.

Absolutely agree. Keeping the SOC above 40% would be ideal, but not always realistic or worthwhile, especially when the choice is between driving an additional 40 miles to a Supercharger with 15 open stalls OR stopping at 40% SOC at an EA station with 4 nozzles, two of which aren’t working, and a line of 3 VW ID4s waiting while two Chevy Bolts are sitting on the two operating nozzles, charging at 48 kW.

(I am partially joking but not totally. In California this happens ALL THE TIME at EA stations, especially since VW was offering “free charging” for a few years, I believe 2021-2023 models? Hopefully we will see those deals expiring soon, but it really seems to be clogging up the EA network. Why pay to charge at home when you can charge for free at an EA station?

)