When to pull the plug?

[JyChevyVolt]

Found a new route. A new record.

 

[Pushmi-Pullyu]

BTW, just to get this out there, my 2013 Leaf does give me the option to charge to 80%. I've never used that option personally, but it is there. I kept reading that Nissan doesn't have any option besides 100% so I wanted to set that straight.

Yes, the option was eliminated in the 2014 model year Leaf, and so far as I know still isn't there.

This was widely reported at the time; for example, in this Green Car reports article.

 

[Cypress]

Yes, which IMHO is why people should take car to make sure any BEV they buy has a range significantly higher than their anticipated daily driving needs. If you have a 200 mile BEV, then only charging to 80% will get you more distance than if you have an 85 mile BEV and you charge to what the car's BMS tells you is 100%, which is more likely somewhere around 90-96%. If you have only a single car and are worried about having to make an unexpected long-range emergency trip, then that single car shouldn't be a BEV; it should be a PHEV or a gasmobile. Many EV owners have two cars, with the other car being a gasmobile, which they can use for those rare emergency journeys.

One size does not fit all. There is theory and there is practice. I've detailed the theory of what will maximize battery life; what you do in practice will have to fit your individual practical needs, not the theory.

I'm an EV advocate, but that doesn't mean I'm going to ignore the reality that at the current state of development, BEVs are not for everyone. The car anyone chooses has to fit their lifestyle, not some ideal.

Despite the hype about the Bolt and Model 3, There aren’t really any truly affordable 200+mile range EVs available. So it is not as simple as just telling people to go buy a car with enough range so that they can do the 80/30 charging rule.

My point is more that if EV advocates are pushing that theory, than the average consumer is not going to want to hassle and will have another reason never to buy an EV.

 

[loomis2]

Yes, the option was eliminated in the 2014 model year Leaf, and so far as I know still isn't there.

This was widely reported at the time; for example, in this Green Car reports article.

Maybe they killed the feature because they realized there are a lot of owners like me that have never used it and have no intention to. EV cars are already range limited. Why would I want to limit it even more? Sure, most days we could get by with setting it to 80% but always having the immediate option to go farther is more important to me.

Still, what harm does it do them to keep the menu option available to people who want to use it? It seems like it takes more work on their part to remove it at that point.

 

[Cypress]

So then, you meant "efficient" in the sense of using more of the stored energy to actually send the car down the road, when comparing BEVs to PHEVs?

Well in general I agree with what I think you are saying, which is that BEVs are more efficient in using energy to push the car down the road than are PHEVs. As you say, PHEVs have to be designed to operate both as gasmobiles and as pure EVs. And just as with anything else, something designed to do two different things probably won't do either as well as something designed to do just one thing. All engineering is a compromise, but some compromises are worse (or less efficient in various ways) than others.

But there is one thing running counter to that, and it's this: BEV drivers worry a lot about range anxiety. Or at least, they have to spend some time planning ahead so they can avoid that as much as possible. And that means that a BEV driver is going to take care to ensure he will wind up at the end of the day with some safety margin of range left in the car. If he thinks he won't be able to do that, then he -- or rather many BEV drivers but not necessarily any individual one -- will drive his other car that day, and that car is likely to be a gasmobile.

I wish we could get statistics showing electric-powered miles vs gas/diesel-powered miles on the basis of drivers, rather than cars. A PHEV driver never needs to switch from his PEV to a gasmobile, since his PEV can switch from one mode to the other. Just how many gas-powered miles are BEV owners putting miles on their gasmobiles because they want to avoid range anxiety from driving a BEV that day?

Anecdotal for sure, but we have a 2014 spark EV, and Subaru Impreza 5-door. We are now a averaging far fewer miles on the ICE, then we have, because we trade off and take the Spark EV for most errands or commuting. Prior to having the Spark we were probably averaging about 10k miles/yr on the Subaru, and 10k miles/yr on our old ICE that the Spark replaced. Have had the Spark EV for 9months and it already has over 10k added to the odometer.

Yes, we sometimes trade so that the person that may have a long trip outside comfort zone for the Spark EV takes the Subaru, but those trips are pretty rare. We are fortunate also, that most places we want to go in the Spark has some charging available nearby.

 

[jdonalds]

Anecdotal for sure, but we have a 2014 spark EV, and Subaru Impreza 5-door. We are now a averaging far fewer miles on the ICE, then we have, because we trade off and take the Spark EV for most errands or commuting. Prior to having the Spark we were probably averaging about 10k miles/yr on the Subaru, and 10k miles/yr on our old ICE that the Spark replaced. Have had the Spark EV for 9months and it already has over 10k added to the odometer.

Yes, we sometimes trade so that the person that may have a long trip outside comfort zone for the Spark EV takes the Subaru, but those trips are pretty rare. We are fortunate also, that most places we want to go in the Spark has some charging available nearby.

Our situation is similar. We either combine trips or share the Clarity. 95% of the time we use the Clarity while the 4Runner sits parked. The only times the 4Runner is used is to tow the boat (6 warm months only), or when it can't be avoided. Our ICE miles are very few.

 

[Pushmi-Pullyu]

Despite the hype about the Bolt and Model 3, There aren’t really any truly affordable 200+mile range EVs available. So it is not as simple as just telling people to go buy a car with enough range so that they can do the 80/30 charging rule.

Perfectly true. I've gotten tired of pointing out that the Model 3 should not be called an "affordable" car; it's more like a semi-affordable one. Ditto for the Bolt EV. Both are far out of the price range of the top ten best selling cars (not light trucks) in the USA.

Despite the hype about the Bolt and Model 3, There aren’t really any truly affordable 200+mile range EVs available. So it is not as simple as just telling people to go buy a car with enough range so that they can do the 80/30 charging rule.

My point is more that if EV advocates are pushing that theory, than the average consumer is not going to want to hassle and will have another reason never to buy an EV.

You have a point there, but there is also a point to be made that if people buy a car advertised as having an EPA range of X, and they find out the actual range is less than X if it's driven at normal highway speed, and the range may be far less on a bitterly cold day, especially if driven at highway speed, then there is going to be a backlash against buying EVs by the general public.

As far as the 80/20 or 70/30 or 60/40 charging rule, well that's just the sort of thing that early adopters have to put up with, in any complex technology. Do you know the Model T had a spark advance lever mounted on the steering column, and the driver had to manual advance or retard the spark when accelerating or decelerating?

That sort of thing was of course replaced by an automatic spark advance system in later models, and I think it won't be long until BEVs are designed to set the proper DoD for the daily charge/discharge cycle, either automatically or at worst with the press of a couple of buttons on the screen.

 

[Pushmi-Pullyu]

Still, what harm does it do them to keep the menu option available to people who want to use it? It seems like it takes more work on their part to remove it at that point.

Thanks, that was the point I was trying to make but I guess I didn't do it well. Sure, a lot of people -- probably most people -- won't want to bother. But you don't have to look very far on EV forum discussions before you see discussion of people wanting to maximize battery life. In fact, there have already been one or two people asking about that on this forum, and it's still pretty new.

 

[Tiralc]

FWIW, another reason to stay plugged in (beyond ability to remotely use climate control on L2) is that if you happen to leave something on (e.g. an interior light), and happen to not use the vehicle for a few days to a week (unusual for most), it might (?) save the 12V battery from discharging. (thunderstorms were already discussed, yes, unplug)

Not sure if the Clarity can do any monitoring and charging of the 12V battery when it is plugged in and off? Sitting in the car electrical "on" (one push over accessory) or turning it on (brake + start) with seat heater on, starts to draw L2 power. No idea if it can do any charge maintenance (either HV battery and/or 12V battery), once first fully charged, if still pugged in?

 

[Ken7]

One thing I've noticed with the Clarity, and it was a similar thing with my Sonata PHEV, is once the battery is fully charged, the charger never comes back on again. I believe we've touched on this before. We were driving the Tesla for several days as the weather turned nicer here, so the Clarity just sat for a few days. Not once did it recharge on its own after the initial full charge.

It's hard to believe that no charge is lost as the car sits there for days. So it seems that either the car won't restart it's charging cycle once its full, or the threshold for a new charge cycle is greater than the range I've lost with the car just sitting there.

 

[Tiralc]

One thing I've noticed with the Clarity, and it was a similar thing with my Sonata PHEV, is once the battery is fully charged, the charger never comes back on again. I believe we've touched on this before. We were driving the Tesla for several days as the weather turned nicer here, so the Clarity just sat for a few days. Not once did it recharge on its own after the initial full charge.

It's hard to believe that no charge is lost as the car sits there for days. So it seems that either the car won't restart it's charging cycle once its full, or the threshold for a new charge cycle is greater than the range I've lost with the car just sitting there.

I remember that, and it is a good and helpful anecdotal observation, but does that mean the Clarity will not do anything while plugged in, if either the high voltage or 12V battery dips below some point? BTW, I leave the Clarity plugged in most all of the time, and I have never seen any significant power draw (on the charge point graph) other than for a single charge, or remote climate operation, or sitting in the car with the seat warmer on, so you may be right.

Also, in the Volt, there were occasions (both Gen 1 and Gen 2) where I did not drive them for several days to a week, and I never saw as much as a bar or single mile of range decrease. Self discharge, while likely present at some level, may just be too small over days or a week to start a new charge cycle.

Just like the technical data we eventually got (thanks to jdonalds) on the details of when remote climate comes on, probably there are Honda tech notes on this subject too.

The more curious me would be tempted to at least try to draw down the 12V battery charge level somewhat, to see if it forces a charge cycle to begin, but not sure I can deal with that sort of experiment right now.

 

[Ken7]

I remember that, and it is a good and helpful anecdotal observation, but does that mean the Clarity will not do anything while plugged in, if either the high voltage or 12V battery dips below some point? BTW, I leave the Clarity plugged in most all of the time, and I have never seen any significant power draw (on the charge point graph) other than for a single charge, or remote climate operation, or sitting in the car with the seat warmer on, so you may be right.

Also, in the Volt, there were occasions (both Gen 1 and Gen 2) where I did not drive them for several days to a week, and I never saw as much as a bar or single mile of range decrease. Self discharge, while likely present at some level, may just be too small over days or a week to start a new charge cycle.

Just like the technical data we eventually got (thanks to jdonalds) on the details of when remote climate comes on, probably there are Honda tech notes on this subject too.

The more curious me would be tempted to at least try to draw down the 12V battery charge level somewhat, to see if it forces a charge cycle to begin, but not sure I can deal with that sort of experiment right now.

And yet the range loss on my Tesla can be easily seen day by day. I lose 2-4 miles/day in my cold garage. The Tesla automatically kicks in a new charging cycle once I've lost about 8-10 miles of range. So it would be a head-scratcher to me why the Tesla battery would be so much more prone to range loss than the Clarity's battery.

I suppose an argument could be made that there's a whole lot more of 'listening' electronics to drain the battery, but still, this is a big difference.

 

[Tiralc]

And yet the range loss on my Tesla can be easily seen day by day. I lose 2-4 miles/day in my cold garage. The Tesla automatically kicks in a new charging cycle once I've lost about 8-10 miles of range. So it would be a head-scratcher to me why the Tesla battery would be so much more prone to range loss than the Clarity's battery.

I suppose an argument could be made that there's a whole lot more of 'listening' electronics to drain the battery, but still, this is a big difference.

I think that's probably it, "more of 'listening' electronics to drain the battery". But, I don't know the answer. I called Honda, but they have finally convinced me that the only way to ask a technical question is to call the dealer. So, I did, and they said they would look into it.

 

[Pushmi-Pullyu]

One thing I've noticed with the Clarity, and it was a similar thing with my Sonata PHEV, is once the battery is fully charged, the charger never comes back on again. I believe we've touched on this before. We were driving the Tesla for several days as the weather turned nicer here, so the Clarity just sat for a few days. Not once did it recharge on its own after the initial full charge.

It's hard to believe that no charge is lost as the car sits there for days. So it seems that either the car won't restart it's charging cycle once its full, or the threshold for a new charge cycle is greater than the range I've lost with the car just sitting there.

I don't find this surprising. In previous years it was commonplace to see advice given to BEV owners to not charge the car if it was above the 80% charge threshold. Leaving the battery pack charged to 100% on a long-term basis is bad for battery life... even if that "100%" is really more like 92-96% of the nameplate capacity for the battery cells. So it certainly makes sense for the pack's BMS to report "no charge needed" even if it has lost a few percent.

I presume you're actually talking about the Clarity PHEV here, rather than the Clarity Electric (BEV), but the lithium-ion batteries used in PHEVs are not that different from the ones used in BEVs.

 

[Ken7]

I don't find this surprising. In previous years it was commonplace to see advice given to BEV owners to not charge the car if it was above the 80% charge threshold. Leaving the battery pack charged to 100% on a long-term basis is bad for battery life... even if that "100%" is really more like 92-96% of the nameplate capacity for the battery cells. So it certainly makes sense for the pack's BMS to report "no charge needed" even if it has lost a few percent.

I presume you're actually talking about the Clarity PHEV here, rather than the Clarity Electric (BEV), but the lithium-ion batteries used in PHEVs are not that different from the ones used in BEVs.

Yes, I was talking about the Clarity PHEV. My point was more in the direction of at what point, if any, does recharging begin without any manual intervention. Let's assume you've lost 10% of the charge while the car is sitting idle for a week or two. I'm sure as the car sits there, the Lithium Ion battery will lose some charge, as they all do. Will the charger automatically kick in once again, or is the initial charge all the car will ever see unless the charge is manually reactivated? Is there any threshold beyond which the charge will automatically kick in again as it does in a Tesla?

I don't think any of us knows the answer to that yet. If someone goes on vacation without the car and is gone for several weeks, then we might have an answer.

 

[Pushmi-Pullyu]

Will the charger automatically kick in once again, or is the initial charge all the car will ever see unless the charge is manually reactivated? Is there any threshold beyond which the charge will automatically kick in again as it does in a Tesla?

While these are all certainly relevant questions, I think the answer in all cases is going to be "It depends on how the BMS (Battery Management System) is programmed to operate".

There's no reason to expect that a BMS from one auto maker is going to work just like a BMS from another auto maker. Nor should we necessarily expect that the BMS for a PHEV is going to work just like the BMS for a BEV, even if it's from the same auto maker.

I see the various charging strategies and choices made by EV drivers as a "negotiation" between the driver and the BMS. Unfortunately, it's a "negotiation" in which the BMS is likely to get the last word, unless you use some hardware external to the car to prevent it. The BMS will never give you as much info as you want, and in some cases -- such as charging a Leaf to less than what the Leaf's BMS tells you is a maximum charge -- the BMS may outright prevent you from making the choice you want.

I realize none of this actually answers any of your questions. I'm just pointing out that there are limits to knowledge, and in these cases our knowledge may be limited to even less than we want for proper planning, and perhaps even less than we need.

 

[Ken7]

It would be so easy for Honda to simply state in the instruction manual what actually happens after the car is charged and sitting there. That would avoid all this conjecture.

 

[Tiralc]

The chargepoint 32A EVSE may (?) be able to shed some light on how much discharge there is over time. Clarity (may need to name it) was last charged at about noon yesterday. It remained plugged in overnight. This morning, about 10am, I unplugged it for 10 seconds and plugged it back in again. According to chargepoint, it took an additional .03 kWh of charging energy (about 0.2% of 14kWh, about a full charge, about .06 miles for a 30 mile deep winter range with highway driving):

If this measurement was made over different time intervals many times, would it be an indicator of self discharge (self battery discharge, plus actual discharge by internal loads)? Or, does the buffer line move too (i.e. is some of that energy going "above" the previous "full charge" point)? Would temperature also need to be recorded and somehow factored in (certainly for milage, but what about just kWh)? What about charging losses (most likely under 15%, possibly as low as 5%).

 

[Ken7]

All valid points, Tiralc. I do think ambient temperatures and internal loads (whatever those may be) are issues. But I do seem to recall trying to charge immediately after a full charge, and I seem to recall it taking a bit more charge time after that. So I wonder if it's not a case of that buffer line moving.

In fact I've seen that same phenomena with other lithium ion batteries, where upon reaching their 'full' status, you can get a bit more charge in them by simply unplugging and plugging them back in.

 

[Pushmi-Pullyu]

Would temperature also need to be recorded and somehow factored in (certainly for milage, but what about just kWh)?

That's certainly a factor. Li-ion batteries have greater capacity when they get warmer, altho from looking at graphs it seems the increase above room temperature is rather minimal. Contrariwise, the dropoff in capacity when the batteries get cold is quite pronounced.

This is one of the reasons why it's quite difficult to get an accurate measurement of the actual capacity of a li-ion battery pack, even for experts: capacity varies by temperature!

On the other hand, internal resistance also rises with rising temperatures, so this reduces the amount of additional range you would theoretically get from higher capacity when the batteries are warmer than normal room temperature.