Charge Strategy for Max Battery Life

M.M. said:
Being an engineer, this got way longer than I intended, so here's the executive summary/tl;dr version:
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Wow, that's just the summary?!?!
:eek: :eek: :eek:

Thank you, M.M., very much for researching that and putting it all together in a coherent fashion!

This is a very complete summary of the theory of how to extend the life of an EV battery, and what to avoid to prevent premature battery aging, and should apply to all plug-in EVs, both BEVs and PHEVs.

Unfortunately, in practice, that advice will still needs some interpretation for individual models of PEVs (Plug-in EVs), because they probably use different percentages of reserve on the "top" and "bottom', and the gauges of different PEVs almost certainly don't report SoC (State of Charge), or permanent loss, in the same way.
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Viking79 said:
Given Clarity has 20 bars to represent about 12 kwh of power, they are probably around 1/2 to 2/3 of a kwh each. Meaning it keeps maybe a 1 kwh or 1.3 kwh buffer. They probably have a little more beyond that they don't use to protect the pack. This means maybe around 2 kwh on the bottom, 12 kwh usable, and 3 kwh on the top?
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Those all look to me like reasonable guesses, but it would be a mistake to simply assume it's all true. For example, on the Leaf, the first bar represents about twice the fraction of total capacity that the other bars do. Perhaps on the Clarity every bar represents an equal amount, as common sense would suggest. But I wouldn't just assume it's so without evidence.

I think it's also reasonable to assume, as you did, a larger buffer on the top than on the bottom, to avoid the problem with premature aging due to charging to near 100%. People are not likely to run their battery down to what the car says is "0%" very often, so a larger buffer on top than on the bottom makes sense for extending battery life. But again, that's just an assumption on the part of you and me. Honda's engineers may have had a reason to reserve more on the bottom than on the top, altho I can't imagine what that reason would be.
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Pushmi-Pullyu said:
Perhaps on the Clarity every bar represents an equal amount, as common sense would suggest. But I wouldn't just assume it's so without evidence.
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I can't say for sure whether every bar represents the same amount, but I can say with certainty that it isn't linear over the full available charge range, since the first bar doesn't disappear until below 90% according to the app (which appears to be correct). If it was linear, each bar would be around 5%, give or take, so either there is an invisible chunk at the top that isn't represented by the bars, or the size of each varies.

At some point I'm going to pay close attention to the app while emptying the pack and write down the % charge at which each disappears and see what the algorithm for the display is.

I should probably do it a couple times, in fact, to make sure that it's consistent, which isn't a given (for whatever reason, the Volt, for example, does a range recalculation sometimes when turned off and back on, at least when it's near empty).

Pushmi-Pullyu said:
Unfortunately, in practice, that advice will still needs some interpretation for individual models of PEVs (Plug-in EVs), because they probably use different percentages of reserve on the "top" and "bottom', and the gauges of different PEVs almost certainly don't report SoC (State of Charge), or permanent loss, in the same way.
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While yes, there are no doubt varying reserves at both ends on every vehicle, there's a fair degree of certainty that the general design is similar because lithium-ion battery chemistry and endurance is well understood, so the bottom-line advice I came up with is going to be pretty much true of any vehicle that doesn't fully charge or discharge its battery.

And one can say with a fair degree of certainty that the Clarity does neither, since at the bottom it actually displays some excess charge, and it would be outright shocking (and a huge design flaw) if it charged to 100%, since the available EV range would start decreasing noticeably in a year or two of regular driving. It would be borderline malfeasance to not make the customer aware that fully charging the vehicle will reduce the battery longevity significantly (like all BEVs that allow 100% charge do, as far as I'm aware).

Point being that no one outside Honda at this point seems to know whether the range is 85-15%, 90-20%, or whatever, but the bottom definitely isn't 0% and the top had better not be 100% (and almost certainly isn't), so the basic advice above is accurate regardless.

The only unknown is whether the car actively cools the battery while plugged in after it's done charging if the ambient temperature is very high, which would modify the extra recommendation regarding storage temperature.
 
Like the Joker said about Batman, “Where does he get all those wonderful toys?”
Seriously, where are you finding all this great Clarity info? Did you have to subscribe to Honda Express Service?
 
Whoops. My bad. I was in such a happy hurry to read anything about our Claritys that I just blew right past where they came from. Thanks.

I grind my teeth over the fact that Honda no longer sells a model year specific service manual for us owners who don’t need or want the hugh expense of buying a recurring subscription to every Honda under the sun.
 
Doesn't regenerative braking affect this?

I also trust Honda has the overcharging thing taken care of as it is such a basic thing.

The only thing in our control is....do we charge every time we are in the driveway? I have been told yes by volt owners. Now I am not so happy with that answer.
We can send stuff to mars but figuring out perfect charging methods for consumer goods is still alluding us.
 
prestoOne said:
Doesn't regenerative braking affect this?

I also trust Honda has the overcharging thing taken care of as it is such a basic thing.

The only thing in our control is....do we charge every time we are in the driveway? I have been told yes by volt owners. Now I am not so happy with that answer.
We can send stuff to mars but figuring out perfect charging methods for consumer goods is still alluding us.
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We could haul one of these

Your friend has shared a link to a Home Depot product they think you would be interested in seeing.

8,000-Watt Dual Fuel Powered Electric Start Portable Generator

https://www.homedepot.com/p/205635157
 
Deploy solar panels? Seriously, it is an issue when parking and plugging in. For example, going to Disneyland. Assuming a totally depleted battery, it would take 2.5 hours to charge, but the car sits there all day, perhaps 10-12 hours. No way to move the car other than exiting the park and killing an hour to move the car.
 
DTC P144A (78): HV Battery Pack Deterioration (High Severity)

Take a look at the attached DTC. I am having a hard time interpreting the chart. I have some thoughts but would like to hear what you guys think.
 

Attachments

AnthonyW said:
DTC P144A (78): HV Battery Pack Deterioration (High Severity)

Take a look at the attached DTC. I am having a hard time interpreting the chart. I have some thoughts but would like to hear what you guys think.
Click to expand...

In general, this is their procedure for determining if cells in the battery have gone bad. If they have gone bad, the measured battery capacity (Ah) at two SOC points yields a delta capacity that will be lower than the default.

Aside from the document's real purpose, the numbers seem to confirm what we know. The chart says the default 'Usable Battery Capacity' is 20Ah (-10 to +10). If you convert that number to kWh, you only get 7kWh (20Ah x 352V) rather than 14kWh that most people see. My guess is that this chart is only for one pack. Recall that there are two packs: Battery Pack A and Battery Pack B. Since Honda chose to label them A and B, the intent is likely for them to be replaceable individually. Assuming that is a correct chart interpretation, our total usable capacity is confirmed to be 14kWh (or specifically 14.080kWh).

I suppose you are having difficulty rationalizing the threshold they have established. Putting the battery capacity threshold down at 25% of nominal will likely result in very few "defects" over the 8yr/100,000 mile warranty period. A pack's capacity would have to drop to 5Ah to trigger the Malfunction Indicator Light. In a worst-case scenario, let's say both packs dropped equally to 5Ah. The total EV range of the vehicle would be 1/4 of nominal or 12 miles. Most owners would likely disagree with Honda that the high voltage battery is not defective so long as the range is above 12.
 
The "Integrated Cooling System for Underfloor High Voltage Devices in PHEV" technical paper over on the SAE website is really interesting. https://www.sae.org/publications/technical-papers/content/2018-01-1184

Don't pay the 28 bucks for it. Just click on "preview document" and you can view the first 5 of the 7 pages and I think the last 2 pages deal with the Clarity Electric.

I want to see if I am interpreting this correctly and forgive me if I am over thinking this (my wife would label me obsessed with the SOH of the battery). It looks to me that there are 3 conditions where the battery is not actively being cooled:

-Parked and ambient temp is above 104F
-Charging and ambient temp is above 104F (this concerns me)
-Coolant is warmer than the battery max target temp of 95F

I gathered that from Tables 1 and 2 and Figure 7. The ambient temp can easily go over 104F when sitting in a hot asphalt parking lot that is radiating heat upward and above inside the cabin, the temp is approaching 130F. I am wondering if I should even charge during the summer at work when those are the exact conditions I am facing. There is no shading around the charging port and the way I have to park to charge, the windshield is under full sun. I have 70% ceramic tint on the front windshield but it still gets hot.

Previously, I thought that I should start charging as soon as possible after a drive, so that the cooling system would be engaged but now I am thinking I should wait until I get home, park the car in the garage and give it a few hours to cool off before starting to charge. Thoughts on this???

Lastly, it would be great if a thermal engineer could Fisher Price to me what X number of watts of heat rejection means. Also it states that the cooling system can cool up to 8 K of the max battery temperature limit. I am assuming K stands for Kelvin, but when I convert that to Fahrenheit it is not making sense. I am just trying to figure out how much heat can the cooling system dissipate at a given temperature.
 
I think I might have answered my own question. The cooling system can cool down 8 degrees below ambient. Since 95 is the upper limit of the battery , we should not charge when it is hotter than 104 or as there will not be any active battery cooling.


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