Preventing battery degradation

[v_traveller]

Good data! Have you ever measured battery temperature at the tail end of a full charge session? I've noticed the TMS running on several different charging sessions when near full charge, both at L1 and L2.

 

[michael]

Yes, and it varies, depending on starting temperature and duration of charging. In any event, I've never seen it above 98 F at end of charging, and in those cases I can hear the TMS running intermittently.

I've never seen the TMS take it below 96, and generally it's stable at 98. As far as I've seen, once it reaches 98, the only way to get it cooler is to let it cool down on it's own, and that's quite slow. As I mentioned before, even the next morning, the battery is generally well above ambient (in moderate weather...)

 

[studio460]

Thanks for everyone's excellent input!

 

[studio460]

• Storing Li-ion batteries at 100% charge.
• Charging batteries while the batteries are hot ("smart" chargers typically prevent this from occurring).
• High number of charge cycles.

Exactly. Particularly that second point- charging batteries while hot is bad for battery longevity. More accurately charging or discharging a hot battery will shorten its lifespan faster than charging or discharging a cool battery . . . Just being hot, if no energy is going in or out of batteries, is not a particularly big deal. Which is why I think remote starting the car that can't be plugged in to keep battery cool is a waste of time.

Excellent observations, dmen. Now, again, I have a 60-mile round-trip commute, so I was planning on plugging in at work for a six-to-eight hour, 120V charge to "guarantee" my trip home. If battery longevity is my top priority, maybe it's best that I should just try to make the 60-mile commute on a single home-charge (it's often only 72-degrees or lower where I live)?

 

[michael]

Based on the best information I can find, being hot and at high state of charge is the MOST harmful thing to a battery. The charging and discharging process are not the problem. The end result of charging (i.e. being charged and hot) is bad. In addition, being at a low state of charge is not a problem (although people keep thinking this is case because it is so with lead-acid batteries).

The problem is that lithium ions migrate to internal electrodes when at high SOC and high temperature. The more time spent in this condition, the more lithium deposited.

Electochemist Jeff Dahn

http://www.dal.ca/diff/dahn/publications.html

has described the charging process as "incredibly benign". He measures the number of ions deposited by determining the Coulombic efficiency of the battery, which is typically something like .9999. The .0001 deviation from exactly 1 represents the lithium left behind. He has demonstrated that this number is determined by battery chemistry, charge level, and temperature. His method would have predicted with three weeks of testing the problems that Leaf batteries have experienced, and that Tesla batteries will last a long time.

I trust him. Check out his lecture on the subject...

https://www.youtube.com/watch?v=pxP0Cu00sZs


Based on his information, I charge only to the extent necessary, and and close as practical to departure time (not upon arrival). Studio 460....my advice is charge to maybe 70% (or whatever is the minimum that will guarantee your arrival with comfortable margin) at both ends of your commute. Do not needlessly fully charge.

 

[hybridbear]

Today was our first day of charging with the 240V EVSE at the full 6.6 kW. I went down to the car shortly before it finished charging and it was making an awful racket. I'm guessing this must be the TMS system. I was down there about 20 minutes before a Go Time programmed to 65F and I opened the door to see if the inside was cool and it wasn't. The car had a very loud buzzing noise similar to that of a radiator fan on an ICE car running at a high speed after the ICE is turned off. Was that the TMS system?

 

[jmueller065]

That was the radiator fan. Open the hood when its running and you can clearly see it. You can open the doors, hood, etc. while its doing the precondition and it won't stop. The only ways the precondition will stop is to either start the car, pull the plug, or delete the go times.

I've found that sometimes the car "forgets" about the go times but then remembers them if I open a door. I'll frequently load up the car for my commute about 5-15 minutes before I leave. Sometimes when I'm only 5 minutes before the go time and the car has forgot, the fan and everything immediately kicks on when I open the door (granted in some instances my timing may be perfect and it just decided at that time to do the precondition).

 

[fbitz777]

I am a brand new and happy FFE owner with just 1000 miles over last 3 weeks;
Anyhow as I read the warranty Ford will replace battery during first 7 years/80k miles and my few observations:

First that would mean 1000+ recharge cycles which from what I read from Lion/Lipo battery technology is a LOT of cycles. I own a lot of tools and model airplanes with high performance Lipo and 100s of cycles is about the limit. Given the recommendations on this thread it would be more like 2000 cycles.

Second 7 years is a lot of time for any battery to last.

Third why would I care about preventing battery degradation IF Ford is willing to warranty that long of a distance and time? Granted they have de-rated their battery by 10% to avoid deep discharge and over charging. Ford is a BIG company and probably built in the price the fact that batteries will fail.

Fourth I would hope that by the time my battery fails (hopefully under warranty) I can get a battery with upgraded technology that would improve the range (the major limitation of FFE)

To put this in perspective Tesla range being 200-300 miles obviously translates to 300 cycles before you get to 80k miles! I am not sure about Tesla warranty miles/years but seems it would be easier on them.

Finally I am wondering if Ford has a way to get out of its warranty obligation on the battery; are there any way they could figure out I "abused" the battery somehow?

Maybe I should have leased instead of buying and not have to worry about all these issues!

 

[WattsUp]

First that would mean 1000+ recharge cycles which from what I read from Lion/Lipo battery technology is a LOT of cycles. I own a lot of tools and model airplanes with high performance Lipo and 100s of cycles is about the limit. Given the recommendations on this thread it would be more like 2000 cycles.

The longevity of the car's battery should be much longer than your experience with smaller, highly-utilized batteries might suggest. The battery in the FFE is not "cycled" as severely as your models and tools.

The battery is never discharged lower than about 10% capacity and is never charged much over 90%. Only the middle 80% or so of the battery's capacity is actually used. The car's battery is also temperature-controlled, unlike your tools and models.

 

[jmueller065]

Hybridbear: Here is a pic of my fan running during the go time this morning:

 

[hybridbear]

That was the radiator fan. Open the hood when its running and you can clearly see it. You can open the doors, hood, etc. while its doing the precondition and it won't stop. The only ways the precondition will stop is to either start the car, pull the plug, or delete the go times.

I've found that sometimes the car "forgets" about the go times but then remembers them if I open a door. I'll frequently load up the car for my commute about 5-15 minutes before I leave. Sometimes when I'm only 5 minutes before the go time and the car has forgot, the fan and everything immediately kicks on when I open the door (granted in some instances my timing may be perfect and it just decided at that time to do the precondition).

So is the fan running for the AC for the cabin or for the TMS? When I heard the fan running the car was not cooling the cabin. I'm quite used to hearing the AC running when the car is preconditioning because we hear that almost every time we go down to leave. This seemed like a different & much louder fan noise.

 

[v_traveller]

So is the fan running for the AC for the cabin or for the TMS? When I heard the fan running the car was not cooling the cabin. I'm quite used to hearing the AC running when the car is preconditioning because we hear that almost every time we go down to leave. This seemed like a different & much louder fan noise.

From your description, my guess is that it's the TMS. By the end of a charge cycle the battery accumulates heat that, depending on ambient temperature, may elevate high enough to trigger the TMS. Also, I thought I read somewhere that charging at nearly full capacity generates more heat. Below is a screenshot of when the TMS went on in my FFE at the end of a charge cycle, ambient was 81F:

Typical charge cycle doesn't have that lump. I have a really short write-up with a typical charge cycle screenshot and a chart from batteryruniversity.com, for comparison:

http://ev-vin.blogspot.com/p/random-images.html

 

[WetEV]

First that would mean 1000+ recharge cycles which from what I read from Lion/Lipo battery technology is a LOT of cycles. I own a lot of tools and model airplanes with high performance Lipo and 100s of cycles is about the limit. Given the recommendations on this thread it would be more like 2000 cycles.

There is at least one Leaf well past 100k miles.

http://green.autoblog.com/2013/12/18/seattle-nissan-leaf-owner-surpasses-100000-miles/

That is well over 1000 cycles. He was still driving it, last I knew, a few weeks ago. I think that there are some Tesla Roadsters with over 1000 cycles as well, and that is a lot more miles. I can't seem to find a link, however.

Second 7 years is a lot of time for any battery to last.

I had a Motorola cell phone that I bought in 2001, gave to offspring well known for destroying phones in 2011 and it was still working until it was put into the washing machine in 2012. Wife bought the same model phone at the same time and she killed the battery by 2007, mostly by running the battery empty too often and leaving on the charger for days at a time.

Want to keep the battery for a long time? Charge just before usage most of the time, don't fully discharge often, don't top off charge often, and keep the temperature reasonable. Somewhat conflicting advice, but perfection isn't required.

 

[michael]

By contrast, I have two friends with severely degraded Leafs.

One was just returned after a three year lease, 22,000 miles and range well under 50 miles. It was garage-kept in Beverly Hills. The problem was that they kept it charged all the time.

 

[jeffand]

A good practice is not to leave the car in a fully charged state for long periods of time.

Example 1: The owner charges his vehicle every time he comes home, even though the car has plenty of range left for the next day use.

Example 2: This owner only charges when the battery is more than 50% discharged, or he needs the extra range for next days use. The owner also dosn't allow the battery to be deeply discharged.

In Example 1 the owner will see the capacity of the battery reduced at faster rate than example 2.
It would not be wise to leave the car plugged into the charger for several weeks at a time. The best practice maybe if the car isn't driven for several weeks isto take some the charge out of the battery. This can be done by taking a short trip, and not recharing the car until it is needed again. For time of 4 weeks or longer the 12 volt battery should be disconnected, or a battery maintainer (tender) should be connected to the 12 volt battery.

 

[WattsUp]

In Example 1 the owner will see the capacity of the battery reduced at faster rate than example 2.

We think... however, there is no long-term evidence (specific for the FFE) to suggest this is true.

 

[jeffand]

I have seen no evidence of this myself, but this doesn't mean that some affect could be seen. It may take 4 to 8 years before a noticeable range reduction is seen. Good care and a little common sense can help extend the useful life of the battery past 8 or 10 years of life. If you do see reduction in range it typically can be attributed to change in driving habits, weather and driving conditions, tire pressure. Your tires will very very slowly loose pressure over time. You should check your tire pressure at least 4 times a year.

 

[michael]

In Example 1 the owner will see the capacity of the battery reduced at faster rate than example 2.

We think... however, there is no long-term evidence (specific for the FFE) to suggest this is true.

I have no reason to believe that FFE batteries are different in this respect than all other lithium batteries of which I am aware. Higher SOC leads to faster deterioration. I'm sure not going to gamble that FFE batteries are immune to this apparently universal characteristic.

I am willing to say that whatever deterioration may happen seems to be quite small, especially when compared to Leaf batteries which suffer obvious degradation.

 

[WattsUp]

In Example 1 the owner will see the capacity of the battery reduced at faster rate than example 2.

We think... however, there is no long-term evidence (specific for the FFE) to suggest this is true.

I have no reason to believe that FFE batteries are different in this respect than all other lithium batteries of which I am aware.

I didn't say they were different... just treated differently.

My point was, the batteries mentioned (in power tools, models, etc.) are treated quite "severely" in contrast to how the FFE batteries are treated. With the tools and models, the batteries are likely allowed to get very hot (while charging and while operating), are frequently charged to absolute capacity, and also frequently deeply discharged. Thus, they have a correspondingly shorter lifespan.

 

[v_traveller]

By contrast, I have two friends with severely degraded Leafs.

One was just returned after a three year lease, 22,000 miles and range well under 50 miles. It was garage-kept in Beverly Hills. The problem was that they kept it charged all the time.

That's a bummer! Do you know if they kept it charged to 100% SOC or 80% SOC? I thought the older LEAFs had that option available.