Is it best to run car to a low mileage before re-charging

[evcar340]

My 2012 FFE has 12000km and it has never been winter driven. Last summer I was getting a charge to 190-210 km range. It is not getting more than 180-185 range. Is it best to take the mileage down to a low remaining amount before re-charging? In the past I was always plugging in to re-charge regardless of mileage left.

 

[edriver]

Battery university has great information on this topic:
http://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries

The conclusion is that bringing the battery down to low SOC before charging shortens its life. High SOC shortens life too. Longest life is achieved with the shallowest possible charge and discharge cycles, with minimum time spent at the high and low ends.

If one really wants to optimize battery life, one should theoretically wait with charging so that it is charged just before each trip and the battery isn't sitting waiting at a high SOC. The trip start SOC should be such that 50% becomes the average SOC during each drive. Obviously Ford and the other EV makers don't tell you this since they want to encourage you to stay charged up and minimize risk of running out of charge.

 

[michael]

I basically agree with what you are saying. I have always been critical of the fact that Ford doesn't offer the option (as does Tesla, Kia, Toyota, Mercedes, etc) to select a higher or lower target state of charge.

The small point I would differ is that you say "...high SOC shortens life too". While a low SOC is may not be desirable, a high SOC is the worse of the two. The Army tested this and found that cells cycled between 0 and 50% SOC lasted not only better than those cycled between 50% and 100%, but also better than those cycled between 25% and 50%.

The Battery University article you quoted says that cells not charged above 3.92 V will last very well, and that this corresponds to about 58% SOC. This is one of the reasons I'm very enthused about the 200 mile class cars...for normal use, it will rarely be necessary to charge beyond this point.

 

[edriver]

Yes, high SOC seems to be worse. Especially if ambient temp is high. Acc to battery university article they started to see massive degradation at 40 deg C. It is understandable then why a LEAF battery regularly lost 25% capacity when parked in hot climates. Does anybody know what the active and passive cooling targets are for the FFE thermal management system?

Like you said it would be excellent if you could set desired charging target like on a Tesla to keep at a lower soc when driving shorter distances. Or when leaving for vacation, plug it in and let sit at 50%, that would be perfect.

 

[Pearl]

You can always setup a Battery Level Alert at 50% (or any level) here:
https://myfordmobile.com/content/mfm/app/site/my-account/notification-settings.html

 

[breeves002]

During the week my car sits at about 50-60% SOC most of the time. I drive to work, then plug into L2 and it charges to full. It may sit at 100% indicated SOC for hours then but I need it to run the cooling all day. I drive home then and let the car sit overnight. It sits in the shade and its usually cool enough that I don't worry about the battery getting too hot. On the weekends my car will sit about 50-60% SOC as well because I don't drive it generally. If I'm planning on driving it more then a few miles, I'll plug it in overnight generally. I wish MFM had more options on partial charging and just an easy way to start charge time while leaving it plugged in.

In the winter it just stays plugged in. With the range being so bad I can't leave it unplugged. We'll see how the battery lasts... Need to do a run down test soon.

 

[michael]

Yes, high SOC seems to be worse. Especially if ambient temp is high. Acc to battery university article they started to see massive degradation at 40 deg C. It is understandable then why a LEAF battery regularly lost 25% capacity when parked in hot climates. Does anybody know what the active and passive cooling targets are for the FFE thermal management system?

Like you said it would be excellent if you could set desired charging target like on a Tesla to keep at a lower soc when driving shorter distances. Or when leaving for vacation, plug it in and let sit at 50%, that would be perfect.

 

[michael]

Yes, high SOC seems to be worse. Especially if ambient temp is high. Acc to battery university article they started to see massive degradation at 40 deg C. It is understandable then why a LEAF battery regularly lost 25% capacity when parked in hot climates. Does anybody know what the active and passive cooling targets are for the FFE thermal management system?

Like you said it would be excellent if you could set desired charging target like on a Tesla to keep at a lower soc when driving shorter distances. Or when leaving for vacation, plug it in and let sit at 50%, that would be perfect.

The cooling cuts in at about 98F. I'm not sure about the cooling but I have the impression it's around 50F.

It's not a thermostat in the sense that it targets some particular value, but rather an overtemp limit.

98 F is too hot for battery life, but it's good for range and for MPGe: MPGe is calculated "wall to wheels" so energy spent cooling during charging reduces the resulting number.

Volt cooling target around 75F. I think this is at least an option that Ford should have offered for those of us who need battery life more than range or efficiency.

Similarly, they should have offered limited charge levels.

 

[michael]

You can always setup a Battery Level Alert at 50% (or any level) here:
https://myfordmobile.com/content/mfm/app/site/my-account/notification-settings.html

Right, but that's pretty lame. It means you have to run outside and unplug the car.

This car is one big computer. It should have been given the option to stop charging at some stated level, not just send out an email.

 

[kalel14]

So the advice here is to keep my battery charged at 50%, giving me a 35 mile range, so that I can keep the battery from eventually degrading and giving me a 35 mile range.

(Lots of work) + (Permanent Range Anxiety) = (I'll just plug the car in every night)

 

[jmueller065]

So the advice here is to keep my battery charged at 50%, giving me a 35 mile range, so that I can keep the battery from eventually degrading and giving me a 35 mile range.

Not really: Use the value charge feature to charge to full late overnight so that it is just topped off before you leave (minimizing the time at 100%).

Once value charge is setup like that you just plug in every night and forget about it.

This is the way I had my FFE setup for 3 years. Once setup I never thought about it and when I turned the lease in the car had the exact same range as when I picked it up.

On the weekends I'd just let the car charge to full when plugged in (which often meant it sat at 100% over the weekend) thus only for 2 out of every 7 days was the car "stuck" at 100%--but then this would also allow the system to perform the balancing.

 

[breeves002]

During the week my car sits at about 50-60% SOC most of the time. I drive to work, then plug into L2 and it charges to full. It may sit at 100% indicated SOC for hours then but I need it to run the cooling all day. I drive home then and let the car sit overnight. It sits in the shade and its usually cool enough that I don't worry about the battery getting too hot. On the weekends my car will sit about 50-60% SOC as well because I don't drive it generally. If I'm planning on driving it more then a few miles, I'll plug it in overnight generally. I wish MFM had more options on partial charging and just an easy way to start charge time while leaving it plugged in.

In the winter it just stays plugged in. With the range being so bad I can't leave it unplugged. We'll see how the battery lasts... Need to do a run down test soon.

Assuming the L2 charger you are using is not a shared resource with other workers, It sounds Like you would be wise to set up a value charge profile for your charge location at work, and use a go-time to let the car know when you expect to leave. If you set the low-cost window to be the last few hours before you leave, it will sit there, plugged-in, running the TMS, but not charging until a few hours before you leave. This allows your car to sit for hours, plugged in, but not at a high state of charge.

My car is generally plugged in about 22 hours a day, but only charges for a few hours before I leave in the morning and again for an hour or so before I leave work to go home. This way the car can use the fans etc. as it sees fit to manage itself, but I don't subject that battery to extended periods at full charge and high temps.

I think I will do this. The only problem I run into is when I need to run somewhere in the day and my battery is at like 25% or less. I have a few co-workers that will let me borrow their cars if they are here though so its only a problem sometimes.