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Discussion Starter · #1 ·
People and sites online say to not fully charge and discharge to preserve battery quality. They suggest staying at the 20%-80% range, unless you are about to take a long trip.

Does anybody know if this is from any large scale studies or is it just urban legend? The manual of the Clarity says that it is fine to charge to 100%.

Do you charge to 100%?
 

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I believe Honda has taken care of this for us. Fom reading this forum, with many things like this we do not need to worry about it. The early adopters of the Volt bemoan the fact that we don't have all the information at our fingertips. The idea probably was to have this car take off in popularity so "regular" people would just drive it. "Regular" meaning not the gearheads in this forum (myself included). From reading here and my own experience I can't even get my wife to use the regen paddles. She needs to get in and drive and not worry about such things. She doesn't care about when to use hybrid mode, charge mode, how much gas should be in the tank, etc. She just drives it. It seems to me that Honda took this all into account and designed the car for people like her.

So yes charge to 100% and trust that Honda figured this all out already.
 

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I would say we can trust Honda that charging to 100% will not kill the battery or cause major loss of range during the life of the car. That's because 100% displayed SOC is probably more like around 90% of actual battery capacity.

The unknown question is whether charging to less than 100% displayed SOC will help avoid some of the inevitable loss of capacity that will occur. Based on what is known about these type of batteries I would say the answer is yes. But the big unknown is how much it might help. Since we don't have any data to go on, all we can do is speculate. If for example it was determined that charging to 100% causes a loss of 10% capacity in ten years, but charging to 80% causes only a 5% loss of capacity during that same time period, many if not most owners would say "meh" and continue charging to 100%. Whereas others might be willing to modify their charging method to squeak out that additional battery life. Keeping in mind that "gear head" hybrid owners are famous for trying to squeak out every mpg from their cars. And even many ICE owners obsess about oil change frequency, and even brand of oil and filter, when all of that effort might keep their engine going 220,000 miles instead of 200,000 miles. But I get the feeling many of them enjoy trying to "beat the system" and get more life out of their cars, and that would be true of some EV and PHEV owners as well when it comes to charging method.

For me personally, I am already doing scheduled charging because of my time-of-use electric rate plan, so for me it's very easy to modify the schedule to stop charging at around 80%. Or simply not plug in if I already have enough charge for tomorrow's driving. For my around town driving 60-80% is plenty, so I am not sacrificing anything in terms of how I use my car. However when I know that I will be driving longer distances I charge to 100%, as I am not going to sacrifice EV range now just for the chance of increasing my future EV range. And if I wasn't on a time of use plan I would probably just charge to 100% and not bother with scheduled charging.
 

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Just charge to 100% each time and enjoy the EV miles. That is what the car was designed for.
I don't think anyone is saying don't drive EV as much as possible. But if someone knows that they are only going to drive a few miles, they don't really need to charge to 100%. If they do they certainly aren't going to hurt their battery. But there is a chance, maybe a slim one, that avoiding full charges except when needed will help reduce somewhat eventual loss of range. Someone who feels this way can manage their charging and still enjoy all the EV miles they want.

The real question is whether it is worth the effort. That's a personal decision. Some people think the effort is minimal and they don't mind doing it for the chance that it might help their battery. Other people are convinced that avoiding charging to full will do nothing for the battery. Others think it might help a little but don't feel that it is worth any effort and prefer to simply plug in each time they get home and let it charge to full. Neither opinion is wrong, it's a matter of preference. For you it is not worth the effort, that's perfectly fine as that is what is best for you.
 

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For me life is too short to worry about coddling the battery. I got bigger fish to fry. Also, I keep my cars for 10 years and then I buy new. I am thinking the Honda engineers built in some extra protection for the battery pack to give good performance in that time frame. So not worried about battery degradation.

Yesterday I had extra mileage to drive. EV went to zero which I almost never do. I put the car in HV charge mode when I was back on the highway and it took 3 or so miles before I started to recoup EV miles. Makes me think it was loading up this buffer that is built in to give extra EV miles (beyond the standard useable 47 mile range) when in regular HV mode. Clarity surely is a sophisticated well designed car.
 

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For me life is too short to worry about coddling the battery.
Yep like I said that's perfectly fine as that is what is best for you.

I put the car in HV charge mode when I was back on the highway and it took 3 or so miles before I started to recoup EV miles. Makes me think it was loading up this buffer that is built in to give extra EV miles (beyond the standard useable 47 mile range)
When ICE first starts up it goes into warmup mode and provides very little power. This can be seen in regular HV mode also. When I am driving in EV on the freeway the EV miles are ticking down 0.1 mile at a time. I switch to HV and the EV miles continue to tick down at the same rate for two or three miles until the engine warms up, then they stabilize.
 

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People and sites online say to not fully charge and discharge to preserve battery quality. They suggest staying at the 20%-80% range, unless you are about to take a long trip.

Does anybody know if this is from any large scale studies or is it just urban legend? The manual of the Clarity says that it is fine to charge to 100%.

Do you charge to 100%?
Yes, 100% on my Clarity all the time. Even if we don't plan on using it all up, you never know if a disaster strikes and the power grid goes off.

Aa for longevity, I am not worried (at least for 10 years) due to the excellent battery warranty.

I think the 20-80% came around with GM's issues with their Volt and Bolt cars.
Bolts are currently being recalled for defective battery cells causing a few fires.

Glad Honda hasn't had any of those issues!
 

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Yes, 100% on my Clarity all the time. Even if we don't plan on using it all up, you never know if a disaster strikes and the power grid goes off.

Aa for longevity, I am not worried (at least for 10 years) due to the excellent battery warranty.

I think the 20-80% came around with GM's issues with their Volt and Bolt cars.
Bolts are currently being recalled for defective battery cells causing a few fires.

Glad Honda hasn't had any of those issues!
Honda's software shuts off the charging somewhere between 80 and 85% full state of charge. Likewise the car switches to hybrid mode by itself somewhere between 15 and 20%. These numbers are based on the advertised size of the battery, vehicle efficiency (miles/KWh), and knowing the actual numbers for my 2017 Volt. In addition, Tesla recommends you set your charge limit to 90% for daily driving to preserve the life of their batteries.

The 20-80% charge limits avoids two of the three largest battery killers - full discharge (#1) and full charge (#2). The third largest battery killer is allowing the battery to get too hot or too cold during charge or discharge. These issues are related to how Lithium Ion batteries work at the chemical level.
 

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Honda's software shuts off the charging somewhere between 80 and 85% full state of charge. Likewise the car switches to hybrid mode by itself somewhere between 15 and 20%. These numbers are based on the advertised size of the battery, vehicle efficiency (miles/KWh), and knowing the actual numbers for my 2017 Volt.
I think we can make a pretty good estimate on the size of the buffer, what we don't know is how much is on top and and much is on the bottom. However my estimate is that charging to full on the Clarity charges to about 90% of actual battery capacity. Here is how I arrived at that estimate:

The battery is 17 kWh. People who have measured the electricity needed to charge from empty to full say that it takes about 14.5 kWh. Empty is 10% SOC, as far as I know that's where people were starting from when they measured 14.5 kWh to charge from empty to full. Some of that is lost due to heat and the actual amount of electricity that makes it into the battery is probably closer to 13 kWh from one estimate that I have read.

0-10% SOC is reserved for the hybrid portion of the battery. In normal driving it usually doesn't drop below around 8%. However if you sit parked with the AC or heater on, or drive very slowly in stop and go traffic, SOC will drop down to around 1% before ICE comes on to start charging. So 1-10% is part of the useable part of the battery. I would think there is probably additional buffer below 0% to avoid the battery getting fully depleted or even close to being depleted.

Assuming that the people who measured started at 10% and charged to 100%, which is a range of 90%, 13 ÷ 90 works out to about 0.15 kWh of actual battery charge for every 1% SOC. Using that number we can figure that the hybrid portion of the battery is about 1.5 kWh of actual charge. Added to the 13 kWh, this makes for a total of 14.5 kWh hours of usable battery (1-100% SOC). If this 14.5 kWh estimate is correct then approximately 15% of the 17 kWh total is kept as a buffer. Again what we don't know is what part of that is on top, and what is on the bottom. If it's 5% on the bottom then it would be 10% on top, which is 90% actual charge. That's the estimate that I use. But again we don't really know for sure.
 

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Tesla recommends you set your charge limit to 90% for daily driving to preserve the life of their batteries.
The comment that I read from Elon is that he suggests 90% so that there is room for regen. The implication being don't charge to full if you don't need it, but if you know you need the full range then charge to 100%. Which is exactly what I do with my Clarity. I have no qualms about charging to full, I just don't do it when I know I don't need it. Easier for me because I am already using scheduled charging because of my time-of-use rate plan, and also my driving is somewhat predictable, i.e. I know when I will be driving more than 50 miles. Not as easy for Clarity owners that don't use scheduled charging because Honda didn't provide an option to set a lower maximum.

We don't have proof one way or the other whether charging to less than 100% SOC will have any appreciable affect on battery range degradation over the life of the car. However more than one person has reported a loss of around 10% since they have owned their Clarity, even when driving the same time of year and the same driving conditions. Confirmed by battery capacity measurements, a new battery is 55 Ah, people who have experienced range degradation get a measurement of around 49 Ah which is about 10% loss. Enough that they are somewhat disappointed that some commutes that used to be all EV now require some time on ICE even for the same time of year. 10% loss after say eight years would be understandable, however that much loss in just a couple of years is understandably disappointing to those who have experienced it. However they also have reported that so far the loss has not increased and range remains stable. Hopefully that trend continues for them.

That being said I doubt that charging to full has caused this, because as far as I can tell most people charge to full, and most people have not experienced 10% loss of range. Most likely something else is going on for these specific owners, like maybe high temperatures, or maybe the car sat on the dealer lot for several months at 0 EV miles and the battery completely discharged. But whatever the root cause, one might wonder if not charging to full (i.e. 90%) would have helped at least partially mitigate their battery degradation. No way to know unless or until there are statistics available that include how these people were charging. My guess is that charging to full makes no difference in these cases, but again we don't know.
 

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Discussion Starter · #12 ·
Thank you folks! I also charge to 100% and came upon those numbers and was wondering. In fact, even when charging to 100%, the Chargepoint meter where I charge never shows more than 15kwh.
 

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I think we can make a pretty good estimate on the size of the buffer, what we don't know is how much is on top and and much is on the bottom. However my estimate is that charging to full on the Clarity charges to about 90% of actual battery capacity. Here is how I arrived at that estimate:

The battery is 17 kWh. People who have measured the electricity needed to charge from empty to full say that it takes about 14.5 kWh. Empty is 10% SOC, as far as I know that's where people were starting from when they measured 14.5 kWh to charge from empty to full. Some of that is lost due to heat and the actual amount of electricity that makes it into the battery is probably closer to 13 kWh from one estimate that I have read.

0-10% SOC is reserved for the hybrid portion of the battery. In normal driving it usually doesn't drop below around 8%. However if you sit parked with the AC or heater on, or drive very slowly in stop and go traffic, SOC will drop down to around 1% before ICE comes on to start charging. So 1-10% is part of the useable part of the battery. I would think there is probably additional buffer below 0% to avoid the battery getting fully depleted or even close to being depleted.

Assuming that the people who measured started at 10% and charged to 100%, which is a range of 90%, 13 ÷ 90 works out to about 0.15 kWh of actual battery charge for every 1% SOC. Using that number we can figure that the hybrid portion of the battery is about 1.5 kWh of actual charge. Added to the 13 kWh, this makes for a total of 14.5 kWh hours of usable battery (1-100% SOC). If this 14.5 kWh estimate is correct then approximately 15% of the 17 kWh total is kept as a buffer. Again what we don't know is what part of that is on top, and what is on the bottom. If it's 5% on the bottom then it would be 10% on top, which is 90% actual charge. That's the estimate that I use. But again we don't really know for sure.
Yeah and we don’t really know for sure where the 17 kWh number comes from either. Is it the capacity from fully charged state to fully depleted state or somewhere less than that?
 

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The comment that I read from Elon is that he suggests 90% so that there is room for regen. The implication being don't charge to full if you don't need it, but if you know you need the full range then charge to 100%. Which is exactly what I do with my Clarity. I have no qualms about charging to full, I just don't do it when I know I don't need it. Easier for me because I am already using scheduled charging because of my time-of-use rate plan, and also my driving is somewhat predictable, i.e. I know when I will be driving more than 50 miles. Not as easy for Clarity owners that don't use scheduled charging because Honda didn't provide an option to set a lower maximum.

We don't have proof one way or the other whether charging to less than 100% SOC will have any appreciable affect on battery range degradation over the life of the car. However more than one person has reported a loss of around 10% since they have owned their Clarity, even when driving the same time of year and the same driving conditions. Confirmed by battery capacity measurements, a new battery is 55 Ah, people who have experienced range degradation get a measurement of around 49 Ah which is about 10% loss. Enough that they are somewhat disappointed that some commutes that used to be all EV now require some time on ICE even for the same time of year. 10% loss after say eight years would be understandable, however that much loss in just a couple of years is understandably disappointing to those who have experienced it. However they also have reported that so far the loss has not increased and range remains stable. Hopefully that trend continues for them.

That being said I doubt that charging to full has caused this, because as far as I can tell most people charge to full, and most people have not experienced 10% loss of range. Most likely something else is going on for these specific owners, like maybe high temperatures, or maybe the car sat on the dealer lot for several months at 0 EV miles and the battery completely discharged. But whatever the root cause, one might wonder if not charging to full (i.e. 90%) would have helped at least partially mitigate their battery degradation. No way to know unless or until there are statistics available that include how these people were charging. My guess is that charging to full makes no difference in these cases, but again we don't know.
We have definite proof that charging to 100% is bad for any LiOn battery. In consumer products (laptops, cell phones, etc.) stopping your charge at 80% extends the battery life by several years. In BEVs the Nissan Leaf so badly mismanged the battery by allowing full SOC charge and not managing heat that many Gen 1 Leafs had to have their batteries replaced under warranty. This is where the widespread belief that EVs need to have their batteries replaced every 5 to 10 years came from. In addition, the chemistry of LiOn batteries explains how full charge and full discharge damage the anode and cathode of the battery.

The Clarity PHEV has a 17.7 KWh battery yet we only get about 13.7 KWh of usable battery. The 17.7 is based on the IRS tables for the Federal Tax Credit. My estimate of 13.7 usable is based on the electric range when compared to my 2017 Volt. Honda has put the same type of buffer on the Clarity's battery as GM put on the Volt's battery - about 2 KWh at the top and bottom.
 

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The Clarity PHEV has a 17.7 KWh battery yet we only get about 13.7 KWh of usable battery. The 17.7 is based on the IRS tables for the Federal Tax Credit. My estimate of 13.7 usable is based on the electric range when compared to my 2017 Volt.
Where do you see 17.7 kWh? The Honda website says 17 kWh, although I don't doubt that is rounded somewhat. I have seen people calculate 17.1 kWh based on the 55 Ah capacity and the 311 voltage of the battery, 55 x 311 = 17.1

On the IRS website all I can find is the amount of credit for the Clarity, not the battery capacity.

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