How to charge a Clarity EV

Well it's sort of a half truth since it is based on the incorrect premise that you can fully charge the battery. While it is true that fully charging a battery can damage it, the fact is that the system does not allow it. What is displayed as full or 100% is well short of a full charge, in order to protect the battery.

If someone did want to charge to less than 100% there is no automated way to do that. Someone would have to set a scheduled timer charge, and figure out on their own how long it needs to charge to reach whatever percent they have decided they want it to stop at.

 

There's a Clarity forum thread about Recommendations for Battery Charging you may want to check out. Because the Clarity PHEV's battery offers "only" 47 miles of EV range, Honda knew that owners would be fully charging their battery every time they plugged in. It's actually good to charge the Clarity fully because that's when the car performs battery balancing to improve battery performance.

In contrast, in a quest for absolute maximum range, Tesla cars are set up with the top-end buffer that is a smaller percentage of the total battery capacity than a Clarity PHEV. Tesla expects owners to worry about the longevity of their battery and take steps to protect the battery. The company recommends owners fully charge only when they need the greatest range their car can provide. Tesla includes a programmed option to limit charging to less than 100% of the maximum capacity (not including the top-end buffer).

EVs also have a bottom-end buffer because Lithium-Ion batteries can be damaged by complete discharging.

 

Have you all bitten on Honda's new SmartCharge? I gave in and with that, you can set a maximum charge level (15% increments counting down from 100%).

Before that, I did do the "set the charge window to produce 60% charge" thing during the pandemic, since it is often 6+ days between long drives to work. The great thing about using a window is that it adds 60% no matter where you start, so plugging in again at 40-50% brought me to full charge for days I was commuting.

I'm still figuring out the other quirks of controlling the SmartCharge settings - that's why I am browsing the forum today.

 

Yes in SmartCharge you can set a maximum. Doesn't mean it's actually going to happen though. You will find many posts by people who found SmartCharge to be completely unreliable, more often than not winding up with incomplete charging. That was my experience also. I have yet to see a post from someone saying that they have been successfully using SmartCharge for any length of time.

The biggest problem is that unlike regular timer charging where the schedule is stored in the car, with SmartCharge the schedule is stored on the Honda server, and there has to be constant real-time communication between the car and the server so that it can do all of its variable start-stop activity. Any communication glitch and the whole thing falls apart.

What exactly is the "set the charge window to produce 60% charge thing"?

 

In my case, on L1 charging, it meant setting my charge schedule to 6.5 hours per night. So if I returned near 0%, after one night I would be at about 70% and I would unplug the car, then plug it in again the night before I need a full charge. Works fine if you know in advance when you will need to go to work or another trip. The 70% charge leaves plenty for a few 10-mi errands as I would get 35-40 mi on the range meter.

 

Got it. A similar method would be to not use timer charging and just not plug in on days when you have enough charge for what you expect the next day. When you do plug in, it will charge to full. In your case that would probably result in charging to full maybe twice a week instead of the once a week using your method.

Although one drawback to either method is that it can result in rarely charging from 0 miles to 100%. I bring this up because I have a theory that cell balancing only occurs when charging from 0 to 100%. There seems to be evidence that the battery capacity Ah value is only updated when charging from 0 to 100%. By itself that's probably no big deal, especially if someone never checks their battery capacity or rarely checks it. However my theory is that maybe the battery capacity is only updated when cell balancing occurs, which if true means that cell balancing only occurs when charging from 0 to 100%. That could also explain why Honda recommends charging to full to extend battery life, which on the surface doesn't make much sense, but it could be related to cell balancing. Of course they don't say anything about charging from 0 to 100%, but probably they are just keeping it simple, they assume that most people will regularly be charging from 0 to 100% fairly often. With the exception of nerds like us who follow various strategies based on theories.

Realistically though we have no idea how often cell balancing is needed to help maintain battery life. Then again we don't have any data or even anecdotal evidence that charging the Clarity to less than 100% might help reduce battery degradation, and if so how much. Same with the theory of avoiding getting down to 0 EV miles if possible. I realize there is information out there about lithium batteries in general, but that's not the same as specific data about the Clarity battery. So it all comes down to which theory or theories one subscribes to, and whether it's worth doing anything about it. It all seems to be kind of a shot in the dark really. What I do is sort of cover my bases, I use easy methods similar to yours to avoid charging to full unless I know or suspect that I will need a full charge. I also try and keep enough charge to avoid getting down to 0 EV miles. And I try not to go longer than a month or two without charging from 0 miles to 100%. I don't put a huge amount of effort into this and I don't fret if any of it goes wrong, because it's just as possible that it makes little if any difference.

 

My observational experience is that the battery capacity value will be reset when one charges from less than 30% SOC to 100% (or the 99% that sometimes occurs). The battery capacity is not reset when the starting SOC is greater than 30%. And, yes, looking at the battery voltage data confirms that the cell balancing occurs when one charges to 100%.

LeoP

 

Regardless of starting point, so for example charging from 95% to full will result in cell balancing? If so that is at least one theory that I can cross off my list.

Good info on the 30% SOC for updating battery capacity, I will try that and see if I get the same result. I know that 0% works because I have done that several times.

 

My statement on cell balancing was not exactly what I have observed. I have been mostly charging to 85% since last Fall. The cell balancing does not occur at 85% SOC charge but does at 100%. I have not tried anything else.

To be completely clear about how low the SOC needs to go to reset the battery capacity after a 100% SOC charge, I have seen the battery capacity reset when starting from 29% and not set when charging from 31% SOC (I have not even tried to get a 30% SOC starting point). Also, I have never seen the SOC below 10% as the engine starts when the SOC gets that low and I do not shut off the engine but always let it warm up fully when it starts. BTW, I use SmartCharge and mostly keep the SOC at or above 40% and at or less than 85%.

LeoP

 

Q: How to charge a Clarity?
A: Plug it in.

 

I think the expectation has always been that it requires charging to 100%, so I guess what we still don't know for sure is if cell balancing always occurs every time we charge to 100%. One theory I have heard is that it does it occasionally not every time, but you seem to have experienced that at least any time you have checked you have seen indications that it is doing cell balancing when you charge to full.

Okay here's another theory, maybe just as easy to disprove. What if 99% is actually the maximum charge, and then the delay we sometimes see from 99 to 100 is when it is doing cell balancing. Maybe sometimes for whatever reason it decides not to do cell balancing (temp too high or something?) and so then it stops charging at 99%, which according to this theory would be just as full a charge as 100%, just without cell balancing. How likely that is I don't know. I have also thought that maybe it actually does reach 100% but by the time we check the status it has already slipped to 99%, and maybe the system won't charge unless you are below 99%. However I think I can disprove that theory all by myself, because the HondaLink app shows what the SOC was at the time charging ended. I have seen 99% in the HondaLink app along with the time that I know charging ended, so this indicates that it actually did stop charging at 99%.

Once I reach 0 EV miles at 10% it will usually cycle between around 8-12%, sometimes as low as 7%.

There actually is a "trick" to get SOC even lower should someone have some misguided reason to want to do so. After the car has reached 0 miles, sit in the car surfing the Internet for a half hour or more with the heat or AC running. SOC will drop to about 1-2% before ICE turns on, then it only charges to around 3% before shutting off, so it will be cycling between 1-3%. Don't ask me how I know this. Actually something similar happens in stop and go traffic with heat or AC, as long as you continue going very slow the SOC will drop way below 10%.

 

...And for economy "plug it in" at home (i.e. connect to residential power). This, to my knowledge gives you, by far, the lowest electrical cost. The 'charge stations' are a rip off, in comparison.

 

Far too many variables for “at home” to always be the lowest cost. Some owners have high rates, or TOU rates may dictate which times are the lowest cost. We have relatively low rates and during daylight hours we can charge from an outlet that receives power from the solar panels. Alternatively, there are some “free” charging stations at a nearby town that we visit frequently. If all goes according to plan, we’ll leave the house with just enough range to get to the charging station, charge up while lollygagging and arrive home with a slightly depleted battery.

Never used a fee based charger or one that requires an app.

 

Yes most pay chargers have crazy rates.

It depends where you live. I am fortunate to have had access to a multitude of free (and usually available) Level 2 charging options near where I work, and in the local area there are several college campuses, grocery stores, restaurants with free charging. And they are starting to pop up in more places.

 

There are free Volta charging stations at several shopping centers in my area. If you go to the Volta website (search Volta charging) they have a map with locations. I have found that not all of the Volta locations in my area appear on Plugshare.

 

You can't damage battery of clarity because we don't have dc fast charger, 120/220 is ok.

It's all come from Tesla supercharger and Nissan leaf with no liquid cooling fast charging times.

Interesting that japanese clarity has fast charging port.

 

I would not spend 1 minute of my day worrying about this. Plug it in every chance you get and leave it plugged in till you need it.

We have a Plug-in-Hybrid we bought new in May of 2019, in May 2022 it will be three years old and has over 37,000 miles on it. It is plugged in at all times unless we are driving it. It is a 2019 Niro PHEV EX and is advertised to get 26 miles per full charge of electric range. After almost 3 years of being plugged in at all time if not being driven it averages about 30 miles per full electric charge.

PHEV's and EV's are designed to be plugged in if they aren't being driven. That is why the all have Battery Management Systems and battery buffers. It is impossible to charge an electric vehicles battery to 100% or discharge it to 0% the Battery Management System and battery buffer will not let this happen.

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. Wouldn't Honda build in safeguards on their vehicles and batteries to guarantee consumer satisfaction? They did not build this wonderful vehicle to have customer after customer agonize over battery management.

Just drive, plug in and enjoy this wonderful vehicle Honda built.

 

Agreed, plug it in and let the brains in the car do the work. I've always just plugged it in at home at the end of my daily commute, and unplugged it again the next morning when I leave. My 2018 base model has over 35k miles and might have lost a few miles of maximum range over the years, but I drive it 35-40 miles per day and I'd be hard-pressed to say the change due to an aging or overcharged battery is meaningful. The effect of snow tires in winter and temperature during overnight charging seem to be much bigger. With snowtires on and cold overnight temps (below 20 °F) my range in the morning ("fully charged") drops to 26-30 miles. The estimated range doesn't recover while sitting in the garage at work even if the day grows much warmer. I assume this is because in whatever algorithm the Clarity uses, the calculated range shown is more about the initial charge and less about the temp of the battery when driving. In summer the range can approach 50 miles, and the overnight charge becomes just a top-up. In any case it's such a nice match to my average daily drive I can't imagine why plug-in hybrids with decent range aren't more of a thing.

 

According to the Battery University of Canada (yes there is such a place) to make your battery to last the longest, keep it between 60 to 80%. That said, if you fast charged daily for each work day and discharged the battery fully for 20 years, you would only lose 10% of your batteries capacity by year 20. At worst you will lose 25% of your range, but that is at 4500 cycles... most people do 100 cycles in a year of normal commuting. In short, it is pretty difficult to reduce the range of your vehicle. Studies also show that most people keep their vehicle 6 years. The battery is the least of your worries.