How to charge a Clarity EV

Certainly most of what you said no one here is going to disagree with. I would also say that few people here are agonizing over this. And thinking about and discussing it does not stop them from enjoying their car. Other than the occasional worried new owner who doesn't understand that there are buffers, it certainly helps to provide them information to help assuage their concerns.

But I also think it's a valid discussion, for those who are interested in it, about charging method as it relates to battery life. Although likely the impact is relatively small over the life of the vehicle, it's of interest to people who enjoy trying to get the most efficiency out of their car, and who expect to keep it for several years. Just like some people enjoy getting into the minutia of tire design as it relates to driving performance, something that I personally care very little about, but I can understand why it's important to some people.

"Think a minute about who knows the most about your vehicle - an experienced Honda Electrical Engineer who designed the battery and management system for it or random internet posters. It is an easy choice for me to pick the most knowledgeable of the two."

I'm pretty sure that no one thinks they know more about the vehicle than the engineers who designed it. But the engineers don't always get to make all of the decisions (marketing people tend to be good at meddling). And the engineers likely don't have complete control over what information gets published. For example the owners manual says, "To help extend the lifespan of the battery, it is recommended that you fully charge the battery each time prior to driving". But we are left speculating just how important this actually is, or what type of impact they are talking about. Realistically we sometimes need to drive somewhere without being able to fully charge. But how often is too often? At what point are we reducing battery life by not always fully charging the battery each time prior to driving? I can give someone my opinion, which is that it's not something to worry about, just charge to full when you can, and that occasional partial charges won't make a noticeable difference. But that's just me speaking as a random person on the internet, I can't provide data to support my opinion. And I can't tell them to just trust the engineers since they know what they are doing, since the engineers (presumably) are the ones saying to charge to full each time to extend battery life. Even though I suspect what happened is the engineers wrote a paragraph or two about this, but whoever edited the owner's manual decided that what they wrote was too complicated for most people and so they condensed it to a single and easy to comprehend sentence, which unfortunately is completely lacking any quantification. Other than the quantifier "each time", which we have to read between the lines and interpret this as meaning "when convenient".

 

I notice that the chart is based on 20 degrees Celsius (68 F). Is there any information available on cycles in more extreme temperatures? People on this forum have been reporting their battery capacity Ah along with their miles and age of the car. It appears that several people have experienced about 9-12% loss of battery capacity in just the first two years of ownership, and usually well below 50,000 miles. They report the same decrease in actual driving range since they purchased the car, closely matching their Ah numbers, and this is not just seasonal variance due to cold temperatures.

They are the exception, but so far we really don't know why this happens to some people. I tend to doubt that charging method has much if anything to do with it, more likely something else like higher temperatures might be a contributor. Perhaps even just occasionally charging at high temperatures. Or maybe extremely low temperatures. Or a dozen other possibilities considering the huge number of variables between owners. Probably there isn't one single factor that affects everyone. Or maybe it's none of that and there are just some inconsistencies in manufacturing of the batteries. But "trust the engineers" doesn't seem like a satisfactory answer to give these people, unfortunately we really don't have anything to suggest to avoid this, or if there's nothing anyone can do and it's just luck of the draw.

 

I enjoyed reading the opinions above. I don't buy into some of the logic and thoughts expressed but I certainly respect them.

I keep my vehicles for a very long time. To get our new PHEV I traded in a 12 year old Prius on it. When we bought the Prius it averaged about 46 mpg. When we sold it after 12 years and over 150,000 miles it was averaging close to 50 mpg. No battery degradation there. We are a two car family and just last year had to trade in our trusty van that was 17 years old with close to 200,000 miles on it. The longest I have kept a vehicle was a Toyota Tacoma Truck with over 280,000 miles.

I plan on keeping our PHEV for at a minimum 10 years, probably more. I will plug it in any time it is not being driven. I should add it is stored in a garage, so the charging environment can get down to 0 degrees or a little below that to well over 100 degrees in the summer. I could care less, the car and charging system have been flawless no matter what the temperature and the vehicle still averages about 30 miles on each electric charge. Its rating when new was 26 miles per full charge. I do my own maintenance as I have on all of our previous vehicles. I am an Electrician by trade and put in our Level 2 charging station in the garage.

With kids and a growing family I can promise you the health of my PHEV battery would not be in the top 100 of my life concerns. The car was made to be plugged in that is why it has a receptacle to receive a plug. The battery is guaranteed for 10 years and the car averages over 50 mpg when it runs on gas.
I trust the Engineers and I trust the Company that made the vehicle and the vehicle itself has proven to be reliable.

My experience with Hybrid/PHEV vehicles has been enjoyable and problem free, not something to worry over.

 

Because the Battery University of Canada is not referring to a specific EV, I assume they mean 60 to 80% of the actual battery capacity, not 60 to 80% of the available battery capacity, which is the capacity not reserved by the battery management software for the upper and lower buffers.

I believe EV designers assume the owners of EVs with small batteries will have range anxiety. Range anxiety prompts these owners to maximize their EV's charge before every expedition to insure they're prepared for unanticipated diversions.

EV designers therefore build a larger (percentage-wise) upper-end buffer into small-battery EVs, accepting the reduction in the already limited range to extend the life of the battery (and to reduce warranty claims). That way an EV owner doesn't have to treat their EV with kid gloves.

So the Battery University of Canada notwithstanding, I'll recite the ABC mantra for the Clarity PHEV and other EVs with small batteries: Always Be Charging. That's what our EVs' designers expected us to do. Let the Tesla owners with their giant batteries and minimal upper-end buffers worry about choosing how much to shrink their EV's range in the hope of increasing battery longevity.

Perhaps my theory also holds for large-battery non-Tesla EVs such as the Porsche Taycan and Lucid Air. I don't know if those manufacturers advise owners to limit the charge percentage on their EVs the way Tesla does, but with batteries that large, Always Be Charging is probably necessary for owners doing their charging at home.

 

The OBD II reports say when the EV battery is 100% SoC as reported by HondaLink, it corresponds to 96.xx% SoC in the full report of the available sensors. So I suspect the upper end buffer in the Clarity PHEV is actually only 3-4%. The lower end range is more difficult to nail down but at 10% SoC (HondaLink), the OBD II sensors report ~20% so it could be around 10-11% absolute buffer at the lower end - but the BMS is pretty aggressive at preventing the SoC from getting down to 0% SoC (HondaLink) / 10% (?) true SoC. So unless someone can collect a data download with the EV at 0%, it will be hard to know for sure.

 

You can get SOC down to 1% by letting the car sit parked with 0 EV miles and the heater or AC running. The same thing happens in stop and go driving when speed stays very low. This does seem to indicate that the lower buffer is pretty good sized if they let SOC get down that far in those situations. Although I wonder why they make an exception in those cases. My guess is they think owners might find it disconcerting to have the engine come on while they are parked for a little while checking email, or waiting in a drive-through lane, and they figure most people won't be parked or stopped that long in those situations. The drawback however is that when you do start driving with SOC that low the engine is more aggressive as it tries to get back up to 10%.

 

Considering the lack of real world data on this topic, your philosophy on how you use your Kia Nero PHEV is probably best. At least it's best for you. It may not exactly correlate to the Honda Clarity because of differences in battery size, power demand and battery management systems, but probably most of the generalities apply to both.

The discussions here are based on the larger picture of overall experiences with EV's, the pool of actual data being gathered on the Clarity, as well as published documents about battery technology in general. Not to say that any of this provides any type of conclusive evidence about the specific effects on the Clarity, but it is a start anyway.

There are a lot of unknowns here and as I said there are some people who are interested in the subject. Very few people who purchase their first EV or PHEV came into it knowing that the battery degrades over time, unless they found that out through prior research. Although an EV owner is probably going to be less concerned about some amount of battery degradation if they are starting out with say 200 miles of range. PHEV owners however tend to be more sensitive about this because of the limited EV range that we start out with. I think most of us have seen first hand that as time goes on our cars are starting to use gas on trips that we previously could have done all EV in the same driving conditions. And those of us that are tracking battery capacity Ah are able to observe the steady march of decreased capacity. And as I mentioned a few people have already lost 10% or more of this already small range in a relatively short period of time, for reasons currently unknown. Not the end of the world, and it doesn't really detract from the overall positives about the Clarity, but understandably it's something that some people are going to at least think about.

Battery degradation is not something that car makers talk about in their advertising, for understandable reasons. And even if, hypothetically, battery life for a particular car could be slightly extended by following particular charging strategies, especially if the recommendation was to not always charge to full, because it would not be to the car maker's advantage to tell people that. People tend to twist information like that into a larger negative than it actually is. I'm not into conspiracies, I'm just talking about the realities of marketing. The engineers could easily build in a large enough buffer to squeak out maximum battery life, however this would reduce the available range, which is not an ideal situation in a competitive environment where shoppers are reading published numbers and making comparisons. I would not be surprised that in many cases a compromise is reached where a somewhat smaller buffer than ideal is put into place that does not provide absolute maximum life, but good enough and will provide acceptable degradation over the life of the vehicle, or for sure at least though the warranty period. The question is, is there at least a little more life that can be gained beyond that with relatively easy changes in how we charge our cars? Or other changes in how we use them? Maybe, maybe not. Hopefully eventually there will be more real world data and analysis to provide some quantitative information, that at least lets people know the possible impacts so that they can make an informed choice for their particular car.

 

I understand your comments.

I think the Honda Clarity is a wonderful vehicle.

I have EV range envy and wish my PHEV could approach the EV range you Honda Clarity Owners have.

The Clarity really hits the sweet spot in EV range for a PHEV in my opinion

 

It is in many ways, but that relatively high (for a PHEV) mileage also has a cost in more ways than one. Although we suspect that in the case of the Clarity Honda subsidized quite a bit of that cost.

In a larger overall viewpoint I think the sweet spot for PHEV's is probably something closer to the national average daily driving distance, which was previously just under 30 miles per day, but is likely currently lower and may never return to previous levels. I would say 25 miles is probably a good PHEV range. This not only reduces cost, but it also can provide slightly more cabin/cargo space, and it also makes it easier to include a more powerful engine so that the car is more enjoyable to drive in HV mode, especially with a depleted battery, making PHEV's more attractive to a larger number of people. Even with 25 miles range the amount of gasoline saved on a weekly basis is still substantial, especially when looking at the national impact on gasoline consumption. Doubling the EV range does not necessarily double the weekly electric usage for everyone.

 

No. It’s hogwash, at best. L1 and L2 charging rates, the only 2 options for charging a US or Canadian model Clarity, are very slow, conservative charge rates. That are roughly .1C and .4C, respectively. The battery has a liquid cooling system and a BMS. Charging will be controlled based on temperature, hot or cold.

You are more likely to heat up the battery while discharging. Driving 80mph in EV will completely discharge the battery in approximately 1/2 hour, or 40 miles. That is a 2C discharge rate. Put another way it is 5x the highest possible charge rate. The BMS will also control discharging if necessary.

Conclusion: Plug it in and let it charge.

There may be, but there is no need. The battery can only be charged to 90%, regardless of what any display may indicate. In my opinion, it is a complete waste of time, for the sake of battery longevity, to do anything other than plug the car in and let the battery charge.

 

I had a Fit EV for 5 years and now the Clarity electric for 4 years. I have always let the car decide when it's full and does battery leveling. The Fit EV had close to 100K miles on it when I turn it in and I calculated that it lost about 10% of its charge capacity by the last year. Cold weather played a bigger factor than any battery capacity degradation. The Clarity lost about 10% capacity in the first year but the last 3 have been pretty consistent.

I did notice something I didn't know before but the Clarity will keep the battery warm during the cold weather when sitting and plugged in. I was working outside and walked by the car and noticed the green charge light on. The car had finished charging the day before and it was about 28 degrees out. I checked the phone app and there was message saying the battery was warming.

 

I didn't know the Clarity Electrics have battery warmers. I'd guess they are the same as the battery warmers in the Canadian Clarity PHEVs--they work only when the cars are connected to an EVSE.

 

I took a look at the Clarity Electric owner's manual and sure enough it has a battery warmer. And yes like Canada it only works when the car is plugged in. Somewhat surprising it has it since Clarity Electric was only leased in California and Oregon. Sure both of those states have some locations that can get below freezing, but there are a lot colder states in the U.S. where the PHEV was sold with no battery warmer.

 

If one is motivated to reduce damage to the battery to extend its life there are some strategies to do so. It depends on a lot of things. If you have a commute that is long enough to fully deplete the EV battery every day, and you fully charge in between, then the impacts are more prominent on the electrodes within each battery cell, and charging at high or low temperatures (especially for our NCM cathode chemistry) induces more damage. As mentioned above the charging rate of L2 is still pretty mild and shouldn't be considered damaging. But in cases where the temperatures are very high or very low the BMS reduces the charging rate to limit any significant potential damage.

In situations where one has a short commute and can charge frequently, thus only having shallow cycles, then the overall damage is lessened, and the damage is more in the mobile lithium itself. Here again temperature plays a role in the damage potential, so on very cold or very hot days it may be advisable to avoid charging or even drive in HV if you want to reduce the potential to have irreversible capacity loss. As well, it is better to do the shallow cycles in the middle of the SOC range. So for instance at a 30% depth of discharge it is better to cycle between 40-70% SOC than 70-100%. Here are some plots from NREL (from computer models based on years of empirical vehicle EV data):





Another helpful strategy is to not leave the battery always resting at very high charge state. Thus if you need to fully charge it is better to plan it so that the full charge completes just before you intend to use the car. Here is a plot that shows the potential damage impacts.



I am not suggesting 'worry', 'concern', or 'agonizing' over the need to 'baby the battery'. I don't lose any sleep thinking about my battery. But I do avoid things that can cause irreversible damage when it is reasonably possible to do so. To each his own.

If you are interested there is a good youtube video that explains the damage: