Running the Battery to 0%

[Grease Lightning]

Thanks. I have the extended range so that does not apply to me right?

It would apply for the ER.

The ER truck has 131 kW usable battery. If you want to use between 20%-85% of SOC you have 65% available so 85 kW. If you are averaging 2.0 mi/kW you have 170 miles. If you can average 2.2 you could eke out 190.

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[DesertEV]

It would apply for the ER.

The ER truck has 131 kW usable battery. If you want to use between 20%-85% of SOC you have 65% available so 85 kW. If you are averaging 2.0 mi/kW you have 170 miles. If you can average 2.2 you could eke out 190.

Got it. I average 2.1 on my truck. I charge to 90%. I am charging right now and it says 85% is 254, but you are saying at 2.1 average I’m really getting 180 or so right?

 

[Grease Lightning]

Got it. I average 2.1 on my truck. I charge to 90%. I am charging right now and it says 85% is 254, but you are saying at 2.1 average I’m really getting 180 or so right?

If you are trying to not get below 20% SOC, yes your usable range at 2.1 mi/kw would be about 180 miles.

 

[DesertEV]

If you are trying to not get below 20% SOC, yes your usable range at 2.1 mi/kw would be about 180 miles.

lol sorry that took so long. Got it. BC that guys is saying don’t go below 20% state of charge.

 

[Newton]

Another reason not to venture into the lower regions is that the SR starts to be power limited at 30%, though you don't really notice it. By the time it gets down to 15% (the lowest I have gone) it has turned into a Tarus with no acceleration.

My dilemma is that I have a fast charger on the way home where 80% means that I arrive at 15%. I don't know if it would be better for the battery to charge a bit longer at that charger to arrive at 20%. Is it worse to "over charge" the battery than it is to run it low? Above 80% (indicated, not what the truck thinks is true) it drops down to 40kW, but hanging around at your last charging stop of the day is worth it time-wise if you can skip a charge stop especially if it is dark and late.

Using the scanner I have noticed that the true state of charge (or what the truck thinks is the true state of charge) is sometimes much less than the displayed state of charge - up to 9% less. Sometimes it is more. The chargers seem to be controlled by the indicated state of charge, ie it will always drop down at 80% indicated even if internally it thinks it is at 73%. So that is wrinkle in the whole thing.

Fortunately I don't fast charge often.

 

[Daragh]

Just because something can do an action and no immediate negative impact is observed doesn't mean it's not going to negatively affect the system in the longer term. Think of running an ICE vehicle into the red, doing it once or twice doesn't show any issue (typically) but its not good for the engine to repeatedly do it.

The Holy Grail of batteries is to increase capacity, charge rates and reliability and to reduce weight and costs.

There are billions of R&D dollars being spent on this all from different angles and materials etc. One of them is solid state batteries, we actually have that technology working now but the problem is "dentrite growth" that kills the longevity. This is a slow process caused over multiple charging cycles.

We are in EV battery infancy, regardless of what Elon and the rest tell us. But research is advancing and I believe in the next 15-20 years (fast in terms of R&D) we will see significant improvement in battery technology.

Here's a relatively recent paper that does a good job of explaining SOH degradation for Lithium Ion Batteries.

https://faraday.ac.uk/wp-content/uploads/2021/04/Faraday_Insights_10_web_FINAL.pdf

 

[Dukhudo]

Another reason not to venture into the lower regions is that the SR starts to be power limited at 30%, though you don't really notice it. By the time it gets down to 15% (the lowest I have gone) it has turned into a Tarus with no acceleration.

My dilemma is that I have a fast charger on the way home where 80% means that I arrive at 15%. I don't know if it would be better for the battery to charge a bit longer at that charger to arrive at 20%. Is it worse to "over charge" the battery than it is to run it low? Above 80% (indicated, not what the truck thinks is true) it drops down to 40kW, but hanging around at your last charging stop of the day is worth it time-wise if you can skip a charge stop especially if it is dark and late.

Using the scanner I have noticed that the true state of charge (or what the truck thinks is the true state of charge) is sometimes much less than the displayed state of charge - up to 9% less. Sometimes it is more. The chargers seem to be controlled by the indicated state of charge, ie it will always drop down at 80% indicated even if internally it thinks it is at 73%. So that is wrinkle in the whole thing.

Fortunately I don't fast charge often.

For road trips, this extra 7% makes a large difference in time. If you need that extra 7% to make it to the next charger, this adds a substantial amount of time at fast chargers.

I just don’t understand why the HVB SOC and HVB SOC Display have to be different if there’s a buffer already built into the battery. It’s limiting the 131kWh usable to even less.

 

[Helium]

I've done it. I can tell you this. 0% means 0%. There's maybe a 2 mile buffer. In a cold snowstorm in Maine, I landed in my garage with the front axle inside and the rear outside, truck DEAD. My Level 2 charging cable was just long enough and it starting charging 10 minutes after plugging in.

How I got into that position? Don't judge, I'm just telling my story. It was fatigue. We were coming come from Montreal, and had to take a HUGE detour around the White Mountains during a snow storm. My last charging stop left me with the exact charge to get home. I saw the charge diminsish ahead of schedule, but in my mind, I was sure that there would be a buffer (did I mis-remember Kyle's F150 episode?). As I climbed the last hill before home, the truck died at the top, 2 miles from home. 0%, no power. I shifted into reverse, and back to forward, and the truck sort of snapped back to life. We white knuckled it down the slight grade to the house for the last 2 miles. As we approaced the garage with 100 yards to go, I realized I was coasting with no power at all. I clicked the garage door opener when within range, and glided 1/2 way in. The truck had some dash lights on, but that was it.

It was a brutal trip, and I've been an EV'er for some time. It was just odd that in my mind, as I was so tired, that I felt I could just will us home. In a way, I did.

This resembles the one time this happened to me. Stopped in Western Oklahoma for a nap, woke up to a cold high wind going in the wrong direction. Truck died across both lanes as I was pulling on to the service road. I shut it down for 30 seconds as traffic was building up on the ramp and service road. I restarted. It came alive and gave me enough power to limp the half a mile or so to the EA charger. I initially had to use a stereotypical EA de-rated charger because the faster chargers were taken. After about 10 minutes, I was able to switch to an actually fast charger and it charged normally.

 

[Helium]

I think it’s perfectly fine to drive the battery down occasionally if needed. You wouldn’t want to do it on a regular basis for longer battery life, but this chemistry will last for a long time.

This chart supports your assertion. The black\blue\red dots across the top are full cycle "capacity checks" taken time to time during 2.5 years of testing.

 

[Zprime29]

I just don’t understand why the HVB SOC and HVB SOC Display have to be different if there’s a buffer already built into the battery. It’s limiting the 131kWh usable to even less.

The HVB is actually around 143kWh ( give or take a couple for my bad memory ), 131kWh is the display usable. So 100% SOC on the display is 131kWh ( in theory, brand new, etc... ).

 

[Citizen0]

I've done it. I can tell you this. 0% means 0%. There's maybe a 2 mile buffer. In a cold snowstorm in Maine, I landed in my garage with the front axle inside and the rear outside, truck DEAD. My Level 2 charging cable was just long enough and it starting charging 10 minutes after plugging in.

How I got into that position? Don't judge, I'm just telling my story. It was fatigue. We were coming come from Montreal, and had to take a HUGE detour around the White Mountains during a snow storm. My last charging stop left me with the exact charge to get home. I saw the charge diminsish ahead of schedule, but in my mind, I was sure that there would be a buffer (did I mis-remember Kyle's F150 episode?). As I climbed the last hill before home, the truck died at the top, 2 miles from home. 0%, no power. I shifted into reverse, and back to forward, and the truck sort of snapped back to life. We white knuckled it down the slight grade to the house for the last 2 miles. As we approaced the garage with 100 yards to go, I realized I was coasting with no power at all. I clicked the garage door opener when within range, and glided 1/2 way in. The truck had some dash lights on, but that was it.

It was a brutal trip, and I've been an EV'er for some time. It was just odd that in my mind, as I was so tired, that I felt I could just will us home. In a way, I did.

I ran out of juice once as well. It was a long trip and I was ready to be home. I was monitoring mi/kwh and adjusting speed on the interstate doing my own mental calculations. In my case I pulled into my driveway and was making the turn into the carport when the truck hit "0". When it says 0, it MEANT 0. I lost all power and the truck immediately stopped. Tried power cycling (I'm in IT, turning off and back on fixes an amazing number of problems). I was not close enough to use the FCSP and ended up using a heavy-duty drop cord and the Level 1 charger to charge the rest of the night.

Everything was fine in the morning, but after reading numerous other reports (at the time, this was early 2023) on the way other EVs had at least some reserved power I was quite surprised by the how the Lightning was completely dead.

I will not repeat that mistake. I have the truck set to max charge to 80% (same for my husband's Mach E) and only charge to 100% before we leave for a long trip. Charging is sparce in rural Georgia, even in larger cities outside of Atlanta (like Augusta). SuperChargers will help, but the mix of their various versions means it is still not perfect and takes research and careful planning. Plugshare is the hidden gem I use before starting any trip.

I need to check my battery pack health again. I'm at 45k miles in less than 2 years and plan on checking it annually.

 

[Dukhudo]

The HVB is actually around 143kWh ( give or take a couple for my bad memory ), 131kWh is the display usable. So 100% SOC on the display is 131kWh ( in theory, brand new, etc... ).

100% display is HVB SOC 97% and it’s around 127kWh. So while there’s extra room to charge, it cuts things off.

But my big problem is that 99.5% display is 117.5kWh which is around 91% HVB SOC. I just wish they would match.

This would also help with DCFC for road trips. As 80% display is 75% HVB SOC. an extra 5% of fast charging could help a lot in road trips.

 

[Zprime29]

100% display is HVB SOC 97% and it’s around 127kWh. So while there’s extra room to charge, it cuts things off.

But my big problem is that 99.5% display is 117.5kWh which is around 91% HVB SOC. I just wish they would match.

This would also help with DCFC for road trips. As 80% display is 75% HVB SOC. an extra 5% of fast charging could help a lot in road trips.

There are numerous things that will effect the voltage of the battery, such as temperature. It was hard for me to process just how much variation the battery can have in capacity, it's not like a gas fuel tank. So when it says your voltage is lower than expected, you need to consider external factors that impact the reading.

There is a buffer built in to prevent us from charging to actual 100% SOC, as that's very dangerous and not good for the battery. We don't want to over charge and brick the battery or worse, catch fire. The display SOC is your useable SOC. When it comes to driving range, that is the ONLY number that matters.

The actual SOC is only useful when determining battery health (as far as I can tell).

 

[Helium]

but make sure you don't let the temperature get too high

After a hundred thousand miles, I have never seen the HVB battery move the needle on the dashboard very much at all. I still wish I had bought the tow package to get that extra insurance it would never move.

 

[Helium]

There is really not much to read in post 30, or are you referring to other posts?
It is just a statement that is not backed up by data (or at least the data is not available).
If these cells are so much worse than others at low depth of charge it would be nice to know a little more.
The fact that running too low or too high has worse degradation is already known.
What would be useful is to quantify the impact on the real SoC over time.
I have driven my truck down to close to 0% (two miles left) and recharged it and the battery stats I can pull from the truck are the same.
What would be the impact if I did that more frequently? How much capacity would I lose after a year for instance? etc., etc.

I don't know if you have seen this chart (I am only a month or so late to the conversation):

https://www.f150lightningforum.com/...epth-of-charge-graph-for-nmc-batteries.19465/

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