Preventing battery degradation

How to preventing battery degradation?

It’s normal for a battery to lose storage capacity over time. This is the result of time and number of charge cycles on the battery. But there are some conditions that will accelerate the aging process.

The lithium battery doesn’t like very cold conditions of less than 10 degrees Fahrenheit. Most EVs have battery pack warmers that help keep the battery at more comfortable temperature when plugged in. The other extreme is when the battery climbs over 90 degrees Fahrenheit. This were an active cooling system is key in keeping battery at a healthy temperature. The battery management system is only active when the car is being driven or plugged in.

The other condition that should be avoided is discharging the battery completely. From what I can find out about lithium batteries they don’t like being completely or nearly completely discharged. Luckily the FFE only allows the battery to be discharged to about 8% level. If the vehicle is not recharged for an extended period of time, would result in the battery losing some of its capacity. So good rule of thumb would be if you have less than 20 miles of range would be to plug in as soon as possible. The lower the state of charge in the battery the more critical it is to recharge.

The same can be said about 100% charging the battery, and being left in this condition. To prevent this battery management system only charges the battery to about 90% of its full capacity. Reading a blog of a Tesla model S owner who claims he has seen no range reduction after two year of ownership. He said he was able to achieve this by programming the charging system to only charging the battery to 80% level. So to reduce the time the battery is left in this high state of charge it would make no sense to recharge the car if you only discharged the battery a small amount (10 – 20%). Someone could program the go times to charge the car up right before one would need to use the car. This would reduce the time the car would be at high state of charge. So let’s say you leave for work at 7 AM then you would want to start charging 4 hours before you would need the car. This would guarantee the car would be completely charged before you would need it.

As a disclaimer I don’t know how tolerant LG chemicals battery is to the above conditions

jeffand said:

How to preventing battery degradation?
It’s normal for a battery to lose storage capacity over time. This is the result of time and number of charge cycles on the battery. But there are some conditions that will accelerate the aging process.

The lithium battery doesn’t like very cold conditions of less than 10 degrees Fahrenheit. Most EVs have battery pack warmers that help keep the battery at more comfortable temperature when plugged in. The other extreme is when the battery climbs over 90 degrees Fahrenheit. This were an active cooling system is key in keeping battery at a healthy temperature. The battery management system is only active when the car is being driven or plugged in.

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The battery temperature management system on the Focus will address this 90% of the time. If you DO leave the focus in very cold weather when not plugged in, the first thing that temperature mgmt system will do is get the battery to the correct temp. So, while this is technically true, the car will handle nearly everything itself.

jeffand said:

The other condition that should be avoided is discharging the battery completely. From what I can find out about lithium batteries they don’t like being completely or nearly completely discharged. Luckily the FFE only allows the battery to be discharged to about 8% level. If the vehicle is not recharged for an extended period of time, would result in the battery losing some of its capacity. So good rule of thumb would be if you have less than 20 miles of range would be to plug in as soon as possible. The lower the state of charge in the battery the more critical it is to recharge.

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Again, this is technically true of Li-battery chemistries. The issue here is a phenomenon called 'cell reversal' which happens when a given Li cell is token to 0% and the cathode & anode actually functionally switch places, making that cell useless (or worse)....however...just like every modern phone or other Li-based device on the market today, the vehicle monitors the SoC (state of charge) for each cell, and will prevent you from getting the vehicle down far enough to actually damage the cell. In effect, when the car hits 0 and shuts off, there is still a few % left in the cells to prevent exactly this kind of condition. This is NOT something you have to worry about

jeffand said:

The same can be said about 100% charging the battery, and being left in this condition. To prevent this battery management system only charges the battery to about 90% of its full capacity. Reading a blog of a Tesla model S owner who claims he has seen no range reduction after two year of ownership. He said he was able to achieve this by programming the charging system to only charging the battery to 80% level.

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This is also *technically* true, but not relevant here. The charging system in the FFE, again like the charging circuits in nearly every high-tech Li device (modern cell phones, etc) understands this behavior. What you'll see if you watch the charging current on a scope is that at the end of a cycle the current drops to less than 1A to prevent overcharging the cells, and in fact will 'float' the charge between (usually, not sure of the values on the FFE specifically) 95% and 99% expressly to prevent this.

What the Tesla owner you mention is experiencing is not his own cleverness in charging the car, but the cleverness of the Tesla battery engineers in preventing the car from damaging itself.


In short: just drive the car as you like, and charge the car as needed, leaving it plugged in as long as you like. There is no chance you can damage the car without doing something extreme (like overriding the charging circuit and charging the HV system directly).

The thermal management system does not appear to cool the battery until it reaches approximately 98 F. Unless the day is very hot and/or the car is in direct sunlight this rarely happens unless the battery is being charged.

The warning "it's hot outside, plug in" appears to look only at the outside air temperature, not the battery. Just yesterday, I got that warning when the OAT was 101 but the battery was at 82 F. If I had plugged in (but not charged) the TMS would have done nothing, nada, zip, and the battery temperature would have risen very very slowly, just as it did when I left it unplugged. If I had plugged in and started charging, the battery would have quickly reached 98 F at which time the TMS would have stabilized the temperature.

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Bill said:

Maybe it's right in front of my face, but I don't see it. Where does the FFE indicate the battery temperature?

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It doesn't. Michael is reading the battery temperature using Ford's diagnostic tool connected to the OBD II port in the dash.

does letting it stay on the charger all night even after full have any affect on possible degradation?

blackbeasst said:

does letting it stay on the charger all night even after full have any affect on possible degradation?

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No. One thing to realize (with all EVs) is that "connected to EVSE" doesn't equal "battery getting charged". The car's electronics will stop (or start) charging the battery only as appropriate.

Another thing to realize (related to the above point) is that what you're calling the "charger" is actually not a charger... it is only an "EVSE" unit (which is short for "Electric Vehicle Service Equipment"). The actual charger is inside the car, and the car's internal systems always control the charging process. In other words, the EVSE is just a very fancy "power supply" for the car -- the car's "wall wart", if you will -- nothing more. And the car only draws power through it when the car wants to.

So, to be clear, there is absolutely no harm in leaving your car connected to an EVSE for any length of time. You are simply saying, "Hey car, here's some power if you need it. Bye now, see you later".

Indeed, that are many advantages to leaving the car connected to an EVSE...

With the FFE, if the battery temperature rises or falls outside of the ideal range, the car's thermal regulation equipment will turn on and cool or heat the battery using only power "from the wall" without sapping any power (and range) from the battery. With the FFE, thermal regulation only occurs when the car is either connected to an EVSE, or is the ignition is on (in which case, the battery's own power will be used to regulate temperature).

Or, if you set a GO time, you can program your FFE to automatically heat or cool the cabin in the minutes before you normally plan to "go" (say, for work, in the morning) using only power "from the wall" without sapping any power (and range) from the battery.

Or, if you set up Value Charging, you can program your FFE (even though connected) to wait until the period of time you specify to actually charge the battery (normally, this would be a time of the day when your electric rates are cheapest.. hence the term "Value Charging").

WattsUp said:

blackbeasst said:

does letting it stay on the charger all night even after full have any affect on possible degradation?

Click to expand...

No. One thing to realize (with all EVs) is that "connected to EVSE" doesn't equal "battery getting charged". The car's electronics will stop (or start) charging the battery only as appropriate.

Another thing to realize (related to the above point) is that what you're calling the "charger" is actually not a charger... it is only an "EVSE" unit (which is short for "Electric Vehicle Service Equipment"). The actual charger is inside the car, and the car's internal systems always control the charging process. In other words, the EVSE is just a very fancy "power supply" for the car -- the car's "wall wart", if you will -- nothing more. And the car only draws power through it when the car wants to.

So, to be clear, there is absolutely no harm in leaving your car connected to an EVSE for any length of time. You are simply saying, "Hey car, here's some power if you need it. Bye now, see you later".

Indeed, that are many advantages to leaving the car connected to an EVSE...

With the FFE, if the battery temperature rises or falls outside of the ideal range, the car's thermal regulation equipment will turn on and cool or heat the battery using only power "from the wall" without sapping any power (and range) from the battery. With the FFE, thermal regulation only occurs when the car is either connected to an EVSE, or is the ignition is on (in which case, the battery's own power will be used to regulate temperature).

Or, if you set a GO time, you can program your FFE to automatically heat or cool the cabin in the minutes before you normally plan to "go" (say, for work, in the morning) using only power "from the wall" without sapping any power (and range) from the battery.

Or, if you set up Value Charging, you can program your FFE (even though connected) to wait until the period of time you specify to actually charge the battery (normally, this would be a time of the day when your electric rates are cheapest.. hence the term "Value Charging").

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yeah i have the "charger" stuck in my head because everything else that you use to plug from the wall to a device is called a charger

jeffand said:

How to preventing battery degradation?

Reading a blog of a Tesla model S owner who claims he has seen no range reduction after two year of ownership. He said he was able to achieve this by programming the charging system to only charging the battery to 80% level.

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Jeff your point is well taken, you are absolutely right extrapolating to the FFE.

To put a finer point on what this owner did, he didn't do any programming to charge a Model S to 80%. The car has a sort of default setting at 80%. The Tesla manual says:
Adjust the charge limit based on your
anticipated driving needs. Touch Set
Charge Limit, then drag the slider bar to
the desired charge level. You can charge
to any level from 50% to 100%. For daily
driving, charge between 50% and 90% to
improve battery longevity. Charge above
90% for trips requiring maximum range.

jeffand said:

How to preventing battery degradation?Reading a blog of a Tesla model S owner who claims he has seen no range reduction after two year of ownership. He said he was able to achieve this by programming the charging system to only charging the battery to 80% level.

Click to expand...

Also realize that because Tesla has a very large battery, the battery receives very little stress from the charging/discharging regimen. The smaller the battery, the more impact use will have upon it. This is one very important benefit to having a large battery.

Right, and this is why I keep wishing, wishing the FFE had an easy way to stop charging at a predetermined point.

jeffand said:

How to preventing battery degradation?
. . .The same can be said about 100% charging the battery, and being left in this condition. To prevent this battery management system only charges the battery to about 90% of its full capacity . . . So to reduce the time the battery is left in this high state of charge it would make no sense to recharge the car if you only discharged the battery a small amount (10 – 20%) . . .

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That aligns with what I've read as well. For what it's worth, here's some Li-ion information from a supporting manufacturer in the field I work in (television). Anton-Bauer is a long-time manufacturer of batteries designed for broadcast video cameras and portable lighting equipment. Their top-line camera battery is a 14.4V, 136 Watt-hour, Li-ion (not sure of the specific chemistry), which originally cost about $1,000 each. These batteries reach EOL in about six years in normal, daily use. Long considered the authority in camera battery technology, here's their information regarding the proper maintenance of their Li-ion camera batteries:

http://mps.antonbauer.com/manuals/DIONIC160.pdf

Note that Anton-Bauer recommends an optimal storage SOC of 50% (so does Sony, by the way). In addition to the definite no-nos (e.g., over-charging, depleting to 0%, etc.), as far as I know, the following are the most damaging causes of pre-mature Li-ion battery life (the last one really isn't a "cause," per se, I'm just stating the fact that Li-ions have a finite number of charge cycles which are fewer than other types of battery chemistries):

• 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.

I know that Li-ions are the most finicky battery chemistries of all to maintain properly, because I've personally killed a pile of my own, expensive Li-ion batteries by employing method #1 alone [Sony V-mount, 14.4V Li-ion camera batteries, LiCoxNiyMnzO2-based inverter batteries, etc.]. I also own a lot of professional photography equipment which requires portable strobe power in the form of pure sine-wave AC inverters. So, I've since sworn off expensive Li-ion-powered inverters, and now only own SLA-based inverters (all but one of my Li-ions were dead within a year--all of my 14.4V Anton-Bauer Ni-MH camera batteries, and SLA inverter batteries are still going strong, years later).

studio460 said:

jeffand said:

How to preventing battery degradation?
. . .The same can be said about 100% charging the battery, and being left in this condition. To prevent this battery management system only charges the battery to about 90% of its full capacity . . . So to reduce the time the battery is left in this high state of charge it would make no sense to recharge the car if you only discharged the battery a small amount (10 – 20%) . . .

Click to expand...

That aligns with what I've read as well.

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Yes, when the FFE says "100% charged", it really means (as near as we can tell) that the battery has somewhere around 90% of its theoretical maximum charge. When the FFE says "0% charged", it really means (as near as we can tell) that the battery still has somewhere around 10% of its theoretical maximum charge.

The FFE battery management system is already doing all the right things to increase battery longevity. Never fully charging, never completely discharging, and attempting to keep the battery at an optimum temperature. There is very little left for us to do. Playing games with how much charge the battery has at any given time, IMO, is just a waste of effort for very little (if any) actual effect. Just drive the car when you need to, and plug it in when you're not driving it.

About the only helpful thing one can do is try to assist in maintaining the battery temperature, by doing the following:

• Always keep the car plugged in when possible, to allow the thermal management system to work.
• If you can't plug in, but it's very hot or cold, you might want to remote start the vehicle regularly (if you care to pay this much attention) to allow the thermal management system to work.
• In hot areas, try to park the car in shade, and off hot asphalt.
• In cold areas, try to park the car indoors.

WattsUp said:

Always keep the car plugged in when possible, to allow the thermal management system to work.

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And, as I mentioned in another post, you might be surprised when the thermal management does come on. I drove about 60 miles on the freeway here in SoCal from around 92 F degrees back to home which was 82 degrees. I parked the FFE in the garage and plugged it in, even though the charge wasn't set to occur until 2 a.m. The fans immediately started up and continued for about five minutes, just cooling the battery down. I wouldn't have thought the thermal management would have needed to come on.

[Quoted from my other thread:]

michael said:

However, once you start charging the temperature goes up faster.

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Yes, that's where I'm a bit confused. At work, all but three spaces are shaded--everything else is completely exposed for the entire day, baking in the hot San Fernando Valley sun, where ambient temps range from 85-108 in the summer. I mostly go into work anytime between midday-to-afternoon, so everything's already hot. So, just assume, I have no shaded area to park on, and can only get a spot on hot, black asphalt. Under those circumstances, I guess I'm supposed to plug the car into the available 120V outlet to engage the cooling system should the internal battery temperature get too hot (accelerated by the radiant heat from the asphalt). But I don't want to add more heat by also charging simultaneously. Can you tell the car to cool the batteries for awhile, and delay the charge a bit once they've cooled? What's the recommended procedure if you must park on hot asphalt everyday?

Sure, if you don't need to charge at all at work to get home you could setup a value charge there that only charges when you are NOT at work. In theory that would prevent it from charging. You would have to creatively schedule it because if the car determines that your value charge schedule isn't long enough (which is frequently the case on Level 1) then it will charge anyway.

studio460 said:

[Quoted from my other thread:]

michael said:

However, once you start charging the temperature goes up faster.

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Yes, that's where I'm a bit confused. At work, all but three spaces are shaded--everything else is completely exposed for the entire day, baking in the hot San Fernando Valley sun, where ambient temps range from 85-108 in the summer. I mostly go into work anytime between midday-to-afternoon, so everything's already hot. So, just assume, I have no shaded area to park on, and can only get a spot on hot, black asphalt. Under those circumstances, I guess I'm supposed to plug the car into the available 120V outlet to engage the cooling system should the internal battery temperature get too hot (accelerated by the radiant heat from the asphalt). But I don't want to add more heat by also charging simultaneously. Can you tell the car to cool the batteries for awhile, and delay the charge a bit once they've cooled? What's the recommended procedure if you must park on hot asphalt everyday?

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Depending on where you work, I might be able to drop by and plug in the OBD scanner and then you won't need to guess about the battery temp.

I take 405 N to 118 W. You anywhere nearby? Do you want to give this a try?



You can force the car to remain plugged in but not charge by setting a value charge to bein at, for example, 7 PM til 6 AM. The thing won't charge until 7 unless you set it to "Charge Now"

But as far as I can determine, if the battery temp is < 98 F, plugging it in will have no benefit (nor any harm).

I got a little relective car cover (just covers the cabin) that seems to work well though a pain to use.

In any case, the actual battery temp is what matters, I truly don't know whether the "hot asphalt" is a factor or not. Without knowing the battery temp, we are all just supposin'


New data point, just in...

This afternoon I arrived in the valley at 4. Outside temp was 99 F so the "plug in it's hot" message popped up, but battery temp was will 80. I parked in direct sun for 2 1/2 hours on hot asphalt, and when I returned the battery temp had risen only to 84. Since the battery temp never approached 98, plugging in would have made no difference.

studio460 said:

• 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.

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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. (Leaf gets the double whammy with DCQC generating more heat and no active cooling during charge or drive.) 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. It might even cause a minuscule amount of harm: say the battery is sitting significantly hot at work for 9 hours. Scenario A, you remote start every 3 hours. Scenario B, you leave it be and ignore the cryptic "hot outside" message. By remote starting, you are drawing power from a hot battery 3 times- the two remotes and then the start of the drive home- vs drawing power from a hot battery only once. Now if Michael's hot asphalt findings are typical, the battery won't get significantly hot in either situation, so you're using maybe 2 kWh (blind guess) that you didn't have to in scenario A, ever-so-slightly adding to the lifetime charge cycle tally for no benefit.
Regarding very cold temps, there's certainly no need to remote start periodically to maximize battery life. Cold does not affect the battery's longevity. A cold battery affects vehicle performance, limiting the available power and the amount of regen possible. But the battery of a driven car warms pretty quickly, bringing performance back to normal. Remote starting once before driving is reasonable, especially for the cabin heating, but in my experience if not remote started, cold performance returns to normal in a few minutes.

studio460 said:

[Quoted from my other thread:] At work, all but three spaces are shaded--everything else is completely exposed for the entire day, baking in the hot San Fernando Valley sun, where ambient temps range from 85-108 in the summer. I mostly go into work anytime between midday-to-afternoon, so everything's already hot. So, just assume, I have no shaded area to park on, and can only get a spot on hot, black asphalt. Under those circumstances, I guess I'm supposed to plug the car into the available 120V outlet to engage the cooling system should the internal battery temperature get too hot (accelerated by the radiant heat from the asphalt). But I don't want to add more heat by also charging simultaneously.

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studio460 - if you go into work midday or later, I don't think you have anything to worry about since your TMS would have been running on the drive to work. What I've seen by doing a single remote start between 1pm and 3pm on hot (103F+) days to run the TMS, the "hot battery" email alert I cut/pasted in another post doesn't get sent to me for the rest of the day, nor does battery performance status on MFM turn red as it did when I actually did have a hot battery.

On the day that I did get the hot battery email alerts repeatedly, I checked MFM and saw that battery performance status was red. Once I remote started, the hourly emails ceased and MFM battery performance status turned green.

Found my original post on the subject: http://www.myfocuselectric.com/forum/viewtopic.php?f=14&t=1206&p=5086&hilit=remote+start+hot#p5086

dmen - I would agree with you that a remote start on a hot day is a waste of time if not for the fact that in my case it seemed to have a positive effect on the MFM-indicated battery system performance and hot battery email alert. I'm thinking that the next time my FFE will be exposed to 103F+ heat I will refrain from remote starting and see if I can duplicate the scenario I described above.

Update on my post above....

Yesterday afternoon, as stated, I drove 20 miles to the San Fernando Valley where the temp was 99. When I parked, in direct sunlight on hot asphalt, the battery temperature was 80. Two and half hours later is had risen to only 84.


Next morning, I set the car to begin charging at 5 AM, and at 7 AM I went to the car. Despite the fact that it had only reached 80% charge and the outside temperature was 65, the battery temperature was up to 95 F.

I drove 40 miles to work at 65-70 and the battery temperature was still 95.

The point is that charging seems to be a major contributor to battery temperature increase, more so that that driving, hot asphalt, etc.