Strategies to combat battery degradation in Clarity

Charging rate is definitely controlled, it takes between 2.5-12 hours to fully charge. Discharging, not so much. Drive 80mph for 20 minutes or so and the battery will be drained. That’s a pretty rapid discharge rate.

I believe I recognize those words.

 

Thanks for your comments.

In general, most on this forum are technical and understand that the BMS handles the charging limits with roughly the stated amount of headroom / foot-room. One of the main reasons for this discussion (and it has been discussed repeatedly in the past too) is that some of us are arm-chair battery engineers, and we can't help but think we can better the longevity that Honda designed into the BMS system. All else being equal, if there are things that can be done that utilize even less of the battery capacity than is allowed by the BMS, then perhaps the battery will last even longer (or with less degradation over a given time interval).

Personally (I am an engineer), I tend to agree with you... I think Honda likely did an excellent job of engineering this machine, and I am going to use it in ways that are convenient to me. If Honda made a big error with their design then we are covered by a warranty. If not, then any efforts to micromanage the battery were wasted !

 

If everything were perfect, and you drove at the 80mph steadily on flat terrain and depleted the battery in 20 minutes then that is, by definition, a 3C discharge rate. In the scheme of this sort of battery, I don't think that would be considered very high at all. As you say, the charging process is definitely limited. At maximum (2 hours for a full charge,) that is only 0.5C.

Clearly there are some pretty large peak currents possible during discharge (200+ amps). They are not sustained though, or you will be arrested for speeding all the time if you try to sustain them !

All-in-all, I kind of feel that neither the charging or discharging rates are especially stressful to the battery.

 

That's what I like about Honda and VW owners. Plenty of smart and well educated owners who figure out ways to improve the cars.

 

Is this accurate or even close to accurate?

Another member had posted "Cruising on a flat highway was around 60 amps. Regen current on a downhill can be high as -100 amps without touching the brake pedal. Touching the brake pedal lightly, regen can go up to -170 amps without friction brake kicking in".

 

Yes. Try it for yourself if you doubt it. You’ll cover 27 miles in 20 minutes. After 30 minutes you’ll have gone 40 miles. You’re not going to get 40 miles in EV at 80mph on flat roads.

 

I agree, it sucks. If I didn't have my JuiceBox Pro EVSE it would probably be really hard to micromanage the charge amount. I usually dispense 20%, which brings my battery level to anywhere between 55%-70%.

If my garage is hot I sometimes delay the charge until 3AM and it'll add 20% in about 30 mins at 24A, and be ready for my commute. Again, JuiceBox Pro has this feature in the app where you can delay the charge pretty easily.

I said "Cruising on a flat highway was around 60 amps" but that's a pretty vague statement so don't get too set on the detail The 60A is at 300-340V range so also don't confuse it with the 240V wall charger amp.

Talking about that 80 mph and depleting the battery in 20 minutes, I believe that. At 80 mph, it looks like 28 miles is the All Electric Range (AER) in below graph from Honda's own publication [Development of Electric Powertrain for CLARITY PLUG-IN HYBRID]. Between 20-40 mph you can go about 55 miles. I believe I can get 60 miles after 2 years, if weather is good and if I charge to 100% as my commute is in that speed sweet spot.



Also, the first post makes it sound like you need to charge to 100% to avoid degradation when that is not true. I think OP accidentally phrased it like that. You want to avoid charging to 100% if you can. I think everyone already knows 100% is actually 90% so no need to emphasize that again. Of course Honda had to build a buffer, otherwise there would be a lot of angry customers after a few years.

 

Is your garage over 140F? If not, charge away.

 

Those of you that heavily limit the charge discharge % over and above what Honda has designed into the car essentially live with the available mileage of a degraded battery from day 1.
Sure, at the end of 5 years you may have more battery capacity available, but I'm not sure why that is so critical if you insist on never using it.

 

Can you site a source where 140F came from? From what I've been reading, any heat accelerates the battery degradation. When my garage is 90F, I can hear the fan running while charging. The BMS is running cooling because the battery needs it. I think it's just better to charge when that extra cooling in not needed (when the garage is cooled off next morning), if I have a choice. I'm pretty sure Honda's battery cooling is effective, but I know it'll heat up my garage even more and higher charge level at elevated temperature isn't good. We're talking about "how to combat battery degradation" in this thread.

For me, even though I keep my charge levels lower than 80% most of the time, I charge it to 100% when I need to, or sometimes by accident. It's not like I'm not using the full available capacity if needed, it's just that I don't need it most of the time so I can choose to keep it below 100%. I do charge to 100% if I know I'm going to use the range.
If you need all the capacity every time, or you just don't like plugging in after every trip, that's fine and I get it.

 

Google. I own a few Lion Energy batteries. I’ve researched Battle Born, Renogy, Victron and others. Granted those are LiFePo chemistry. Lithium battery manufacturers, in general, specify maximum operating and charging temperatures in the 135-140F range.

The fan coming on at 90F just means the system is operating as designed. If the batteries are 140F or more, the BMS should not allow charging until the batteries reach a lower temperature. Plug it in and forget about it.

 

Battery University states over 86F is considered elevated.

 

But is it detrimental to the longevity of the battery? If so, how significantly will the battery be damaged?

Driving in EV at 65F could warm the batteries to 86F. Should we never operate the vehicle in ambient temperatures above 86F?

77F, or somewhere in that neighborhood is optimal, yet Lithium batteries can be operated in temperatures below freezing and up to 140F.

Honestly, if we’re going to stew over normal operating temperatures for batteries, it might be worth considering an ICE vehicle.

 

Apparently so according to the experts there.
I am only adding to this discussion, I do nothing special in regards to battery care, IMO it's not worth fretting over it. I charge the battery without regards to ambient temperature. It gets charged to full twice a day (sometimes even more) from completely empty due to my extensive driving. I drive 40K a year, the battery is getting a good workout everyday, but I don't worry about it. I've already got almost 50k miles on it.

 

Just like the hypermilers who go to extremes to get 80 mpg out of their hybrid cars, some of us find it an interesting challenge to maximize battery life. For Tesla owners, typical daily drives use about 10% of the battery (30-40 miles). That's extremely low depth of discharge (DoD), which is one of the best things you can do to minimize battery degradation. Thus, the average person with a BEV can just drive it and pretty much not worry about the battery. For Clarity owners, 10% is only 4.8 miles so it's not practical to do that. The Clarity battery will not last as long as a BEV battery because the typical daily DoD is far greater and most owners to charge to full every day (which BEV cars advise against). Thus, anything we can do to extend battery life essentially extends the life of the car (the labor cost to replace the battery is likely more than the cost of the battery itself so few of us would consider doing it down the road).

You don't need to worry about high ambient temperatures too much (unless you live in a desert state). The first radiator (positioned in front of the A/C condenser, which nicely protects the condenser from debris strikes) functions to cool the battery when necessary. The second radiator (positioned behind the condenser) is for the engine. The Nissan Leaf was notorious for rapid battery degradation because it is air cooled (there was a class action lawsuit because of that). The Leaf provided a real world example of why the battery needs to stay cool. Also, although you can safely discharge the battery with temps below freezing, you should never charge the car if the battery temp is below freezing because that damages it and US Clarities don't have battery heaters. The Canadian Clarity and most BEVs have battery heaters for this reason. They will use some of the juice to warm the battery above freezing before it starts charging.

 

Some degradation doesn’t end the life of a battery. You may have pointed out the Achilles heel of the BEV, the battery. If the Clarity battery degrades 30%, it will still have about 30 miles of EV range and will continue to perform flawlessly as a hybrid.

It will be interesting to see how the 17kWh battery holds up over time. Personally, I think a bad cell will be a more likely outcome than a battery that drops below ~66% of the original capacity.

If the battery takes a dump and there are no PHEV’s available at that time, my next vehicle will be one powered by an ICE.

 

Here in hot south Texas one “strategy” we’ve learned over the past decade of owning plug-ins is this: When you can, save EV miles for the final commute home in the evening so the ICE is “cold” when it’s parked in the +90f garage. The hood/front end feels warm but not hot to the touch.

Next, set timer to finish charging (slightly over 2 hrs on L2 for the Clarity) before departure time the next morning so the pack doesn’t sit very long fully charged. In our scenario, this gives the pack approx. 9 hrs to “chill” before the charge cycle begins and about 30 minutes sitting full before departure.

In the beginning, we’d just plug in and walk away while listening to the roar of the fans (volt and c-max). Just in case we needed EV range for something that evening. We almost never do so using hybrid mode for those rare occasions is now “OK” for us. The beauty of dual-fuels.

Speaking of the volt, a volt battery engineer traveling with the pre-production test drive tour back in 2010 told me in person this about LiOn batts and temperatures, “If you’re comfortable, the battery is too.” Easy enough.

FWIW

 

This.

Most failures on early HEV/PHEV’s are individual module (or blocks) not the entire battery. The first failures under warranty were handled by replacing the pack but as they figured things out they saw that they could just replace the bad modules instead (still a lot of labor involved tho’).

I’ve done this with the NiMh Prius modules. We call it the wack-a-mole approach and it works OK for a while but eventually the whole pack will need replacing once they age out. This is approx. 10-20 years depending on LOTS of variables (climate being a big one). Fun fact: most module failures are located in the center of those air-cooled packs.

 

I have the Honda OEM evse running on 240v at ~11a... charges the car at a relatively quick pace without heating up the battery as much as it would at peak charging at ~30a.