Best practices to preserve battery life??

[michael]

Anyone have any solid knowledge about procedures to maximize long term battery life?

First question is charging rate...I have access to both 3 KW and 6 KW EVSEs. Intuitively, the slower charging rate seems easier on the battery, but I have no reason to know this is really the case. Anyone know for sure? What long term benefits, if any, from slower charging? Both will be adequate to recharge me overnight or during the work day.

Second question is where on the battery's SOC is it happiest? I need about 55% of my battery to get to work and the same to get home. So one option is to fully recharge both places, run the battery between 100% and 45%. Another option could be to only let it charge to 80% like they do in Leaves, and run it between 80 and 25%. I understand this is less important in the FFE due to the battery thermal management, but is there some advantage nonetheless?

I don't know of any way to automatically make the FFE terminate charging before completion (like the Leaf provides) so there is a hassle factor as well in trying to monitor and terminate charging before completion.

Anyone have solid info on these or any other ideas?

Thanks!

 

[dmen]

Anyone have any solid knowledge about procedures to maximize long term battery life?

Short answer is no.
Everyone has their ideas, and I'm happy to share mine, but my ideas are not solid evidence. Ford has chosen to share next to nothing on this topic so I don't think solid knowledge is available. Only when this crowd has been driving for 20-30k miles can we start to sort out who's starting to see capacity loss and how driving/ charging patterns affect that.
If you're really concerned, take advice from Leaf experience. If you don't need the full range nor the time saving of a 6kW charger, don't fully charge and use the 3kW. At best your car lasts longer and at worst your car lasts as long as it otherwise would. We can chat in a few years and see how your capacity compares to mine, which I frequently charge to 100% on a 6.6 kW EVSE.

 

[Right123]

Unfotunatley dmen is right. Since everyone has under 20K miles it's hard to tell what can slow the capacity loss, but there are a few tips that generally aplies to all lithium ion batteries. Regarding your first question if you do have the time, the 3kw charger would be ideal since we do know that batteries like to be charged at a slower rate. As for your second question, it's perfectly fine to charge your car to 100% because it's really only charging the car to around 85% because the car has a battery thats able to a hold a capacity of 23kw, but the car only draws about 20kw when it displays 100%. I know that Nissan has an option to where you can charge the Leaf's battery to either 100% or 85%, but Ford doesn't. Ford automatically only charges the battery to 85%, so you will never be able to access 100% of the batterys capacity. Another key factor to capacity loss is heat. Whatever you do try to avoid parking in the direct sunlight and try to park in a garage and if you do have to park in the direct sunlight, than roll down the windows by just a tad to let the heat out while being parked. The reason is beacuse heat is one of the main contributors to capacity loss. Batteries don't like it when it's hot so therefore they start to degrade. This is generally proven by Leaf's because Leaf's in Phoenix tend to have the most capacity loss than any other region. Other than that there is really nothing else you can do to extend the capacity life. Don't worry though because if you follow all of these procedures, than your battery should only degarde 3-5% per year (Based on if you drive the vehicle eveyday and where you live.) I hope this helps.

 

[WattsUp]

As for your second question, it's perfectly fine to charge your car to 100% because it's really only charging the car to around 85% because the car has a battery thats able to a hold a capacity of 23kw, but the car only draws about 20kw when it displays 100%.

Actually, I suspect the FFE battery charges to about 95% of the total 23 kWh capacity.

I think Right123 is forgetting that no lithium-ion battery is ever purposely discharged to absolute zero, so there's likely something around a 10% (2.3 kWh) "buffer" of charge maintained at all times to protect the FFE battery against full discharge. For driving around, by all accounts, the FFE has access to about 19.5 kWh of "usable" stored charge. The 10% buffer is not usable for driving.

So, we have:

2.3 kWh (non-usable buffer) + 19.5 kWh (usable) = 21.8 kWh = ~95% of 23 kWh

In any case, I'm of the opinion that there is really no use in "second-guessing" the FFE battery management system. Personally, I simply charge opportunistically and, by luck, happen to leave my FFE slightly discharged every night (which is the bulk of the time it spends not driving) after my short commute home (since I usually charge at work and not at home). I feel that this will probably lead to pretty optimum treatment of the battery.

Also, remember the Leaf owners have to worry/do more because their battery is not temperature-managed like the FFE's, so you can't always compare the best advice for Leaf or other EV owners to what might be the best for FFE owners. Again, I tend to think that the FFE will, on its own, manage the battery sufficiently for long life, and I don't think it's worth knocking yourself out implementing special routines to "manage" the battery yourself, which really nobody will have any idea has helped or hurt until a few years from now. If the experience Tesla had with their Roadster batteries is any indication, the temperature-managed of the FFE should fair much better than the "air-cooled" one in the Leaf.

Best thing, along the lines of what Right123 has already said, is to just "help" your FFE by keeping it cool when possible (park in garage, shade, etc.). I'm not sure 3.3 kW vs 6.6 kW charging would make any real difference. Higher current charging potentially hurts the Leaf, because 6.6 kW charging generates more heat, but that is something the FFE can cope with just fine.

 

[hcsharp]

I second the comments from WattsUp and Right except for a couple things depending on your climate and driving habits. If you have a commute that uses 50% of your capacity normally, I don't subscribe to the theory that discharging from 80% to 30% is a good idea. Doing so ignores the fact that when driving the car it's easier on the battery to be at a higher SOC. If you are driving down the highway at 65mph your car will draw more amps at a lower SOC than it will at a higher SOC. More amps means more heat. Li-Ion cells also have more internal resistance at lower SOC, so even if you drove slower you would still heat up your pack more. Heat is your worst enemy. The best solution is to charge it full shortly before driving. Use Value charging as Ford calls it.

Having said that, there are benefits to charging at a low rate for a few minutes when you first get home. The car cools the battery more aggressively when it's charging. Your pack will be warm from your long ride home and plugging it in at about 1.5kW (240v) will cool it off. Then it will rest at a cooler temp until you do your Value charge several hours later.

The other thing is charging in the winter if you live where it's quite cold. Plug it in all night so it maintains the car at a consistent temperature. Fortunately Ford won't charge the car with the battery below freezing which would ruin it. It heats it up first. But heating it up fast will sometimes mean you don't have consistent temps throughout the pack. The coolant is on the outside of the cell where the temp is measured, but the inside of the cell may still be frozen or close to it. Or there may be pockets around the edges that are slower to heat up. Charging in that state would destroy your battery. Better to leave it plugged in when you get home and let it "value charge" as Ford calls time-of-use charging.

As for charging at 3kW vs 6, both of those are very conservative rates for the FFE battery. With the good cooling system in the FFE I don't think it will make any significant difference except possibly in the winter when the pack is maintained at about 40 deg F. Li-Ion cells don't have the same capacity to charge fast when they are colder. We're planning to use 4kW this winter and resume 6kW in the spring. But even that will probably make little or no difference.

 

[v_traveller]

If you have a commute that uses 50% of your capacity normally, I don't subscribe to the theory that discharging from 80% to 30% is a good idea. Doing so ignores the fact that when driving the car it's easier on the battery to be at a higher SOC.

Information on batteryuniversity.com is contrary to that:
http://batteryuniversity.com/learn/article/how_does_internal_resistance_affect_performance

"The internal resistance of lithium-ion is fairly flat from empty to full charge. The battery decreases asymptotically from 270 mW at 0% to 250 mW at 70% state-of-charge. The largest changes occur between 0% and 30% SoC."

This article covers other types of batteries (NiMH, NiCd, lead-acid)... perhaps you were thinking of the lead-acid battery internal resistance as a function of SoC? If you have an information source that is contrary to this, could you share it with us? I love learning about this stuff!

-----

To answer the original post, I think there's relatively solid advice out there that pertains to EVs in general, not specifically to our beloved FFEs. Suggested reading:

http://insideevs.com/understanding-battery-capacity-loss-from-a-four-year-bmw-electric-trial-veteran/
http://www.plugincars.com/eight-tips-extend-battery-life-your-electric-car-107938.html

If you read those two, then read some of the stuff on batteryuniversity.com, you can draw some pretty good conclusions about how to baby your battery:

http://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries

 

[hcsharp]

If you have a commute that uses 50% of your capacity normally, I don't subscribe to the theory that discharging from 80% to 30% is a good idea. Doing so ignores the fact that when driving the car it's easier on the battery to be at a higher SOC.

Information on batteryuniversity.com is contrary to that:
http://batteryuniversity.com/learn/article/how_does_internal_resistance_affect_performance

"The internal resistance of lithium-ion is fairly flat from empty to full charge. The battery decreases asymptotically from 270 mW at 0% to 250 mW at 70% state-of-charge. The largest changes occur between 0% and 30% SoC."

That article assumes a constant C rate of charge/discharge at each SOC tested. That wouldn't be the case with an EV. Even if the FFE chemistry has a flat internal resistance curve plotted against SOC, you would still draw more amps and generate more heat at a lower state of charge. Heat is your worst enemy. So I would stand by my contention that driving at a higher SOC is better for battery longevity.

However, if the article is correct about internal resistance vs SOC and if the FFE chemistry is the same, then this statement that I made would be incorrect (probably is):

Li-Ion cells also have more internal resistance at lower SOC, so even if you drove slower you would still heat up your pack more.

I may have been confusing it with Pb because I can't remember my source. Thanks for the correction.
In any case, the main reason many of us bought a FFE instead of a Leaf is the conservative approach to battery longevity taken by Ford. Overall I don't think there's much you can do to hurt it.

 

[v_traveller]

That article assumes a constant C rate of charge/discharge at each SOC tested. That wouldn't be the case with an EV. Even if the FFE chemistry has a flat internal resistance curve plotted against SOC, you would still draw more amps and generate more heat at a lower state of charge. Heat is your worst enemy. So I would stand by my contention that driving at a higher SOC is better for battery longevity.

Ah! I get it now, I think. Lower SoC = lower voltage, therefore more current is needed to produce a given amount of power (watts) versus a higher SoC. More current = more heat, given a fixed resistance. Did I get that right?

I'm typing this as I'm pushing up my beat-up taped-together black-rimmed eyeglasses with my index finger.

 

[dmen]

As I said, everyone has their ideas... they all seem reasonable, and it's probably prudent to follow those suggestions if possible. But none of those suggestions come from solid knowledge about FFE in particular. I thought that was the original poster's request.

So Ford has apparently done extensive testing on battery life through a program called Key Life Testing. I can't find results or details on this testing, just articles describing it on industry sites. It looks like the testing was focused much more on driving techniques and weather. I'm not sure if they looked at variables like keeping state of charge on the higher end/ keeping at lower end/ regularly going from very high to very low, charging at 6.6 vs 3 vs 1.44 kW, etc. It doesn't look like they tested effects of leaving the car sitting at high state of charge for several days, sitting in the cold for several days, sitting plugged vs unplugged for several days, etc, because the testing involves constant repeated batter discharges simulating different driving conditions. Anyway, this is what I would consider solid knowledge/ evidence.

I'm not ready to trust that FFE's Thermal Management System works flawlessly. Dealing with MFT and SSN issues personally, and hearing about people's 12V battery dying in 2 days, doesn't instill confidence. Haven't there been several posts of folks being texted by their cars with an "I'm hot" message while on plug? Is this consistent with a flawless TMS? Don't get me wrong- I like this car- but I'm not ready to leave it all up to Ford. Sure, don't go through hoops to try to make the battery last as long as possible- you're probably not going to enjoy your EV experience that way. But if you can do things that might prolong the use of your car without inconvenience, why not? Because Ford says you don't have to worry about it? Yeah. Good reason.

On a related note, I think it is very important for the FFE community to have solid usable battery capacity / capacity loss data. We don't have "bars" to lose like Leaf drivers, but we can see how much energy we use from a full battery to 0 range. I would encourage everyone to occasionally do a full discharge like this, say every 10k or 15k miles. As Wattsup will remind you, discharging to 0 doesn't completely tap out the battery so you wouldn't have to worry about damaging your battery by doing this. My car showed a capacity of 19.8kWh at around 2500mi. When I get to 12500 I'll do it again.

 

[WattsUp]

Haven't there been several posts of folks being texted by their cars with an "I'm hot" message while on plug? Is this consistent with a flawless TMS?

Yes, but the TMS doesn't run when the car is turned off, not plugged in, and possibly simply getting hot (e..g, outside in the sun, absorbing heat from hot asphalt, etc.). That usually when the texts come, and are to be expected given enough heat and time. You are right, though, some people have received the texts at unexpected times (me included), such as when the car was plugged in and charging.

The weird texts notwithstanding, I suppose another bit of advice then is, if you must park your car in heat, and it is possible to also leave it plugged in, then do so. It will be able to run the TMS when it gets too hot.

 

[unplugged]

But if you can do things that might prolong the use of your car without inconvenience, why not?

The one thing I have done is that if I don't need to charge, I don't. Before I started reading about some simple ways to increase battery longevity, I would charge it to full every night. I have found that I can wait a couple of days or more and so I wait until I have about 20 or less miles remaining before I charge. Many who have commutes that require a full charge can't do this, but for me it is just knowing what my plans are and if I have enough energy left, I don't charge.

 

[WattsUp]

(deleted)

 

[hcsharp]

The one thing I have done is that if I don't need to charge, I don't. Before I started reading about some simple ways to increase battery longevity, I would charge it to full every night. I have found that I can wait a couple of days or more and so I wait until I have about 20 or less miles remaining before I charge. Many who have commutes that require a full charge can't do this, but for me it is just knowing what my plans are and if I have enough energy left, I don't charge.

Like I said earlier, I believe this is worse for your battery than charging every night. Ideal would be if it was charged full every night so it finished within a couple hours of when you start driving. I won't repeat everything in my earlier post. In summary, driving on a battery at a lower state of charge heats it up more. Heat is your worst enemy, worse than storing at a high SOC, which is never very high on a full FFE.

I read some research that showed discharging much below 40% is worse than shallower but more frequent cycles to 60%. Can't find the source right now. Maybe someone else knows?

 

[dmen]

The problem: The trip summary necessarily indicates the kWh consumed by the motor from all sources, and is in no way relative to the energy originally stored in the battery. The difference is subtle, but important.

Put another way, the energy usage shown in the trip summary includes that gained from regen, as well as that originally stored in the battery.

Unless I'm missing your point, you are incorrect. The counter does not simply display the kWh consumed.
You are ignoring the fact that when energy is captured by the regen system, the trip summary energy usage decreases accordingly. So when the energy you regained is then used, your counter is back where it started before that energy was captured. Say you drive steadily using 5 kWh, then brake and recapture 200Wh. The counter goes from 5.0 to 4.8. When you use up that 200 getting back to speed, the counter is at 5.0 again.

Look at it another way. You believe the Wh/mi average displayed at the end of each drive, correct? If you reset the trip summary at the beginning of your drive, its Wh/mi will match. This average is mathematically related to the mi and energy use also displayed in the trip summary. If this efficiency number takes recaptured energy into account, the energy usage display necessarily does as well.

You'll also note the trip summary doesn't reset between charges. You can continue "adding" to the total kWh consumed for as long as you wish.

Yeah, which is why you would reset the trip summary at the beginning of your capacity testing drive, with a full battery. And which is why you wouldn't have to do this all in one drive. You just would have to not plug in between drives while performing the test. When you get down to a few miles of range left, pull into your garage and turn the heat on high until you get the 0 range warning.

 

[WattsUp]

Unless I'm missing your point, you are incorrect. The counter does not simply display the kWh consumed.
You are ignoring the fact that when energy is captured by the regen system, the trip summary energy usage decreases accordingly.

No you're not missing it, and you're correct.

I had only ever really observed the total kWh increasing, and noticed that the energy usage from multiple trips would add up. The times at which the "energy consumed" decreases can be subtle and not always apparent as the display only changes in units of a hundred Wh.

Thanks for the correction. (I actually went out and drove around until I was convinced... which didn't take long.)

I still wonder, tho, if the final energy number at the end of a trip is completely accurate, due to some possible amount of "slop" from the constant additions and subtractions of consumed and recaptured energy (not to mention how exactly those amounts are measured). That said, it maybe the best measurement we have.

Q: Presumably, it is possible to capture enough "external" energy (e.g., gravity-assisted) to make the display say 0.0 kWh again? And... what happens if that continues? Will the display go negative?

 

[unplugged]

The one thing I have done is that if I don't need to charge, I don't.

Like I said earlier, I believe this is worse for your battery than charging every night. Ideal would be if it was charged full every night so it finished within a couple hours of when you start driving. I won't repeat everything in my earlier post. In summary, driving on a battery at a lower state of charge heats it up more. Heat is your worst enemy, worse than storing at a high SOC, which is never very high on a full FFE.

I read some research that showed discharging much below 40% is worse than shallower but more frequent cycles to 60%. Can't find the source right now. Maybe someone else knows?

My reading of the articles supplied by v_traveller show that charging more often is more harmful than waiting to charge, so long as the charge isn't depleted. Perhaps I am misinterpreting the articles.

All of my charging is to a full charge because I charge at 2 a.m. I would prefer not to keep my FFE at a full state of charge for several days in some cases. I believe that the FFE temperature management keeps heat at a minimum.

 

[hcsharp]

My reading of the articles supplied by v_traveller show that charging more often is more harmful than waiting to charge, so long as the charge isn't depleted. Perhaps I am misinterpreting the articles.

You are. There are at least 3 articles on Battery University that reference studies showing that multiple shallow charges are better than fewer deep charges, assuming the overall kWh are equal. Here's a quote from this one: http://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries

Similar to a mechanical device that wears out faster with heavy use, so also does the depth of discharge (DoD) determine the cycle count. The shorter the discharge (low DoD), the longer the battery will last. If at all possible, avoid full discharges and charge the battery more often between uses. Partial discharge on Li-ion is fine; there is no memory and the battery does not need periodic full discharge cycles to prolong life, other than to calibrate the fuel gauge on a smart battery once in a while.

The other articles discuss something called micro-cracking which is the reason that multiple shallow charges are better than one deeper charge. Micro-cracking shortens the life of the cell and it's much more likely to happen on deeper discharges.

All of my charging is to a full charge because I charge at 2 a.m. I would prefer not to keep my FFE at a full state of charge for several days in some cases. I believe that the FFE temperature management keeps heat at a minimum.

Of course the FFE thermal mgmt does the best it can, but as others have said, it's better if you can give it a little help. The best way to help is to prevent your pack from heating up in the first place. You wouldn't leave it in direct sun on hot pavement and shrug it off by saying "The FFE temp mgmt keeps heat at a minimum." There's no question it heats up more when you drive at a lower SOC. When you get home and don't charge your car for several hours like you do, then it will often sit and soak at a more elevated temperature than it would if you hadn't let it get so hot to begin with. You can believe what you want though.

You are right that it's better not to let your battery sit for long periods at a high SOC. But the effect of doing so is not as bad as heat. Ford never lets it charge high enough in the first place to cause any significant acceleration in capacity loss. And if your battery is cooler, the effects of storing at a high SOC will be reduced. It's quite possible that you're right in your case where you don't drive for a few days.

 

[EVfuture]

I will be away from home for a week soon and the car won't be driven at all. It's stored in my garage and will be cool, since winter's fast approaching. Temperatures outside are starting to dip below freezing now where I live.

Should I leave the Focus plugged in for the week while I'm away or charge it fully and leave it unplugged?

I'd prefer the battery's thermal management system to be active, which I believe only works when the car's plugged in. Please correct me if I'm wrong.

If I do leave it plugged in, should it be in the 120 outlet or 240 V EVSE?

 

[WattsUp]

I will be away from home for a week soon and the car won't be driven at all. It's stored in my garage and will be cool, since winter's fast approaching. Temperatures outside are starting to dip below freezing now where I live.

Should I leave the Focus plugged in for the week while I'm away or charge it fully and leave it unplugged?

I'd prefer the battery's thermal management system to be active, which I believe only works when the car's plugged in. Please correct me if I'm wrong.

You are correct, the battery temperature is only maintained when the car is turned on, or turned off but plugged in.

As far as maintaining temperature while you're away, the choice would appear to be to leave it plugged in. The owner's manual uses this phrase in a few places:

Keep vehicle plugged in when not in use to maintain proper battery temperature.

It doesn't say 120V or 240V, but both should allow the car to maintain temperature. Presumably, 120V is adequate since that's all the car comes with.

It if it was me, I'd leave the car plugged in for the week given the near freezing temperatures. But, if you didn't, I think the car would be fine; it's only one week. But, if you do leave it unplugged, I would not leave it with a very low battery; maybe at least 75% charged.

 

[EVA]

EVFuture - before you leave for a week, you might want to test your car plugged in for two days and not use it. Or have the recall done before you leave.

I had a sad experience with my 2014. Leaving it plugged into 110V for two days fully charged and not driving it at all, the 12V battery was completely drained. The problem was finally fixed at my dealer with a programming update and the car is now fine. It had nothing to do with accessories left on or plugged into the car - something killed the 12V battery while it was charging.

It would be super bad if you came back after your week away to find the 12V battery dead.