Best Practice for battery preservation

dbsb3233

Well-Known Member
First Name
TimCO
Joined
Dec 30, 2019
Threads
54
Messages
9,297
Reaction score
10,812
Location
Colorado, USA
Vehicles
2021 Mustang Mach-E FE, 2023 Bronco Sport OB
Occupation
Retired
Country flag
So then the graph is accurate and doesn't need to be normalized right?
If they're considering a cycle 100% of the battery, then the vast majority of the chart is pretty moot because it's well beyond the average life of a car.

For instance, let's look at the worst line (black). At 1000 cycles, we're still at a decent 91% of original capacity. 1000 * 88 kWh = 88,000 kWh @ 3.5 miles/kWh = 308,000 miles. That's way longer than 99% of the public would ever keep a car. Even an EV. People tire of their cars long before then, even if still running well. They want newer features, new paint, new seats, fewer stains/dents/scratches, etc.

The realistic "play it safe" line is the 25-75 one. At the same 1000 cycles, it's at 93%. So 91% vs 93%. Pretty minor difference.
Sponsored

 

ajmartineau

Well-Known Member
Joined
Jun 23, 2020
Threads
31
Messages
1,358
Reaction score
1,951
Location
Washington
Vehicles
2021 Mach-E
Country flag
We know from other batteries than have been around for 10 years that these are best-case laboratory numbers. I'm pretty sure my car will not spend its entire life at 68 degrees F. like the graph portrays (even in Seattle). I would use this graph for a powerwall.

Also, notice the 1C rate on the side. 1C is 98kW (or 75). That's about 130hp. That's slow speeds and mid-range charging.
Fast charging and discharging is more degradation, high temps is more degradation, etc...
 

zhackwyatt

Well-Known Member
Joined
Dec 18, 2019
Threads
14
Messages
1,603
Reaction score
2,616
Location
Arizona
Vehicles
'21 InfBlu Prem MMEx Past: '13 C-Max '98 Explorer
Country flag
If they're considering a cycle 100% of the battery, then the vast majority of the chart is pretty moot because it's well beyond the average life of a car.

For instance, let's look at the worst line (black). At 1000 cycles, we're still at a decent 91% of original capacity. 1000 * 88 kWh = 88,000 kWh @ 3.5 miles/kWh = 308,000 miles. That's way longer than 99% of the public would ever keep a car. Even an EV. People tire of their cars long before then, even if still running well. They want newer features, new paint, new seats, fewer stains/dents/scratches, etc.

The realistic "play it safe" line is the 25-75 one. At the same 1000 cycles, it's at 93%. So 91% vs 93%. Pretty minor difference.
I wonder how that compares to cell phones. My last phone was at 60% of the original capacity after 3 years.

We know from other batteries than have been around for 10 years that these are best-case laboratory numbers. I'm pretty sure my car will not spend its entire life at 68 degrees F. like the graph portrays (even in Seattle). I would use this graph for a powerwall.

Also, notice the 1C rate on the side. 1C is 98kW (or 75). That's about 130hp. That's slow speeds and mid-range charging.
Fast charging and discharging is more degradation, high temps is more degradation, etc...
My car will definitely not live in ideal conditions (116F in summer), so I want to baby it as much as I can.
 

dbsb3233

Well-Known Member
First Name
TimCO
Joined
Dec 30, 2019
Threads
54
Messages
9,297
Reaction score
10,812
Location
Colorado, USA
Vehicles
2021 Mustang Mach-E FE, 2023 Bronco Sport OB
Occupation
Retired
Country flag
I wonder how that compares to cell phones. My last phone was at 60% of the original capacity after 3 years.
Doesn't compare well. EV battery packs are far more sophisticated, with battery management systems, thermal cooling, controlled charging, and each cell is just one of hundreds sharing the load.

Cell phone batteries are single units that are typically abused by users with poor charging and draining patterns. After 2-3 years, they're usually pretty shot. Which is especially frustrating since so many phone manufacturers have stopped offering replaceable batteries.
 

zhackwyatt

Well-Known Member
Joined
Dec 18, 2019
Threads
14
Messages
1,603
Reaction score
2,616
Location
Arizona
Vehicles
'21 InfBlu Prem MMEx Past: '13 C-Max '98 Explorer
Country flag
Doesn't compare well. EV battery packs are far more sophisticated, with battery management systems, thermal cooling, controlled charging, and each cell is just one of hundreds sharing the load.

Cell phone batteries are single units that are typically abused by users with poor charging and draining patterns. After 2-3 years, they're usually pretty shot. Which is especially frustrating since so many phone manufacturers have stopped offering replaceable batteries.
Sure they are more thermally controlled, but charging/discharging, etc. seems like its pretty constant on a car. Every time you brake/regen its charging too. Obviously it's more complicated and is charging individual cells some times and others other times.

I dunno, my only point is Lithium Ion prefer temperate temperatures and 50% charge. How much you want to handle that is a choice each person makes I guess. Maybe in a temperate climate you don't have to worry about SOC as much. In the Valley of the Sun maybe I can compensate by managing the SOC more actively.

Obviously there is a warranty, but I'd like to not have 70% degradation if I can help it.
 


ChasingCoral

Well-Known Member
First Name
Mark
Joined
Feb 3, 2020
Threads
375
Messages
12,402
Reaction score
24,516
Location
Maryland
Vehicles
GB E4X FE, Leaf, Tacoma, F-150 Lightning ordered
Occupation
Retired oceanographer
Country flag
  • Like
Reactions: pb3

dbsb3233

Well-Known Member
First Name
TimCO
Joined
Dec 30, 2019
Threads
54
Messages
9,297
Reaction score
10,812
Location
Colorado, USA
Vehicles
2021 Mustang Mach-E FE, 2023 Bronco Sport OB
Occupation
Retired
Country flag
Ford doesn't seem to have decided completely on this:
Ford Mustang Mach-E Best Practice for battery preservation Screen Shot 2020-10-08 at 7.22.34 PM


So it seems their answer depends on L2 vs L3 charging.
That's pretty consistent with what we've heard in general. Not only is it a PITA to charge full-time on DCFC, it's bad for the battery to do it frequently.

But I expect few buyers are gonna do that anyway. If they don't have convenient L2 charging at home (or maybe work), a BEV is a pretty bad fit.

But it's good to see Ford say that L2 charging to 100% should be a non-issue. Lower power, less heat, little degradation.
 

pb3

Well-Known Member
First Name
Phil
Joined
Jun 24, 2020
Threads
6
Messages
116
Reaction score
202
Location
California Central Coast
Vehicles
Lincoln MKX, Toyota 4Runner, MME Premium AWD ER (order accepted!)
Occupation
Retired
Country flag
And remember, because of the buffer, charging to "100%" is probably only charging to maybe "90%".
 

dbsb3233

Well-Known Member
First Name
TimCO
Joined
Dec 30, 2019
Threads
54
Messages
9,297
Reaction score
10,812
Location
Colorado, USA
Vehicles
2021 Mustang Mach-E FE, 2023 Bronco Sport OB
Occupation
Retired
Country flag
And remember, because of the buffer, charging to "100%" is probably only charging to maybe "90%".
It would be interesting to see how that 11% buffer is allocated between top and bottom. I would kinda guess more of it would be at the bottom, since the charging curve taper (on DCFC) is already custom-tailored to protect the top end.

But I really have no idea.
 
 




Top