Strategies to combat battery degradation in Clarity

neal adkins

neal adkins

Active Member
All batteries will eventually fail. That said, what are some of things we can do-or not do to reduce degradation and keep our ev batteries in the best health? Have some people who live in extreme cold or hot places noticed loss of range etc?
Tesla owners talk about only charging to 80 percent but one member of this forum who did this and regularly drove up a significant grade, noticed a sharp loss of range. I think using hv charge mode may help when climbing long grades by reducing discharge rate of battery. Here are some of the things i have picked up from my own experience and on this forum that lend to ev battery degradation:
1) rapid discharge (batteries get hot)
2) car sitting with a full charge in high ambient temps.
3) Car sitting for long periods of time with no charging.
4) cold weather operation.(looking for input on this)
5) not regularly charging to 100 percent.
 
neal adkins said:
All batteries will eventually fail. That said, what are some of things we can do-or not do to reduce degradation and keep our ev batteries in the best health? Have some people who live in extreme cold or hot places noticed loss of range etc?
Testla owners talk about only charging to 80 percent but one member of this forum who did this and regularly drove up a significant grade, noticed a sharp loss of range. I think using hv charge mode may help when climbing long grades by reducing discharge rate of battery. Here are some of the things i have picked up from my own experience and on this forum that lend to ev battery degradation:
1) rapid discharge (batteries get hot)
2) car sitting with a full charge in high ambient temps.
3) Car sitting for long periods of time with no charging.
4) cold weather operation.(looking for input on this)
5) not regularly charging to 100 percent.
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Also, how much range loss is normal?
 
I think 2 and 3 are more important and can be avoided in a practical sense. There is a spreadsheet documenting battery capacity loss, you can find it in battery capacity check threads. Bottom line is that it will happen like all EVs but it is not going to impact the driving experience for a long time. At 100k miles you can expect to have about 35 miles EV range instead of the original 48 miles.
 
Lithium ion battery engineer here, lifetime modeling is a big part of my job. Items 1, 3, and 4 will not impact your battery's life. Items 2 and 5 will have a significant on your battery's lifetime.

In general, calendar aging (the reduction in capacity and increase in resistance from just sitting) follows an Arrhenius relationship. In other words, the hotter the battery gets it degrades at an exponentially faster rate. The resting state of charge or voltage of the battery is a bit more complicated but you can also think of it to be an exponential relationship.

Not charging to 100% will also significantly impact the lifetime of the battery. The lower you keep the charge SOC, the better. Same thing goes for discharging the battery. In general, you'll get more energy throughput from the battery with a lower depth of discharge and a lower charge SOC.

For all practical purposes, the practice is to not charge your car until right before you use it. And if you're going to park it all day during a hot summer, try to keep it in the shade.
 
Dr. Kris said:
Lithium ion battery engineer here, lifetime modeling is a big part of my job. Items 1, 3, and 4 will not impact your battery's life. Items 2 and 5 will have a significant on your battery's lifetime.

In general, calendar aging (the reduction in capacity and increase in resistance from just sitting) follows an Arrhenius relationship. In other words, the hotter the battery gets it degrades at an exponentially faster rate. The resting state of charge or voltage of the battery is a bit more complicated but you can also think of it to be an exponential relationship.

Not charging to 100% will also significantly impact the lifetime of the battery. The lower you keep the charge SOC, the better. Same thing goes for discharging the battery. In general, you'll get more energy throughput from the battery with a lower depth of discharge and a lower charge SOC.

For all practical purposes, the practice is to not charge your car until right before you use it. And if you're going to park it all day during a hot summer, try to keep it in the shade.
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Thanks for weighing in. Since this my first plug-in hybrid I am continuing to educate myself on this topic. I found it interesting that some of my gut instincts were actually affirmed in an article about ev batteries. You also affirmed that it's best to charge the car just before you drive it in order to avoid the car sitting with 100 percent soc, wich could be a reason not to always use a level 2 charger (less time at 100 percent soc.).
Here's an article I found interesting...https://www.motortrend.com/news/ev-lithium-ion-battery-life-tips-tricks-advice/
 
Dr. Kris said:
Lithium ion battery engineer here, lifetime modeling is a big part of my job. Items 1, 3, and 4 will not impact your battery's life. Items 2 and 5 will have a significant on your battery's lifetime.
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@Dr. Kris,
Regarding Item 2 (sitting with a full charge at high ambient temps)... Is there a temperature below which this effect becomes insignificant?
If you can avoid direct sunlight (in a garage, or similar, maybe 90 degrees F or lower worst case) is this effect still important?

I (like probably many other people) tend to plug in immediately when arriving home with a low battery. I may not even use the car for several days, so it will sit there at 100% (well, not really 100% because of the buffers built into the BMS)...

Also, Item 5... 100% is not really 100%. I think an indication of 100% is really a cell voltage of 4.08V. Does this largely mitigate Item 5?
 
Agree. I tend to charge when I get home too so it's ready in case I have to go out unplanned but more importantly I'll forget :)
 
Dr. Kris said:
Not charging to 100% will also significantly impact the lifetime of the battery. The lower you keep the charge SOC, the better. Same thing goes for discharging the battery. In general, you'll get more energy throughput from the battery with a lower depth of discharge and a lower charge SOC.
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You are saying that not charging to 100% will significantly impact the lifetime of the battery. Many, or at least myself, might interpret this to mean that not charging to 100% would negatively impact the lifetime of the battery. However, you go on to essentially say that avoiding 100-0-100% charge cycles would be advisable.

We know that the targeted cell charging voltage in the Clarity is 4.09xx volts. This represents a SOC of ~90%. I do not know the low voltage cutoff parameter, but would suspect it to be in the 10-15% range.

Personally, I’m not a fan of micromanaging the BMS. Extracting as many 90-10-90% charge cycles out of those batteries is my goal.
 
Landshark said:
Personally, I’m not a fan of micromanaging the BMS. Extracting as many 90-10-90% charge cycles out of those batteries is my goal.
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I do agree with you here, and don't have any plans to begin micromanagement either unless there is something that can easily fit my existing modus operandi.
 
We already have almost 50k miles on our 2019. The batteries get drained at least twice a day, sometimes more. I use the car like a normal car. No issues.
 
Landshark said:
"We know that the targeted cell charging voltage in the Clarity is 4.09xx volts. This represents a SOC of ~90%. I do not know the low voltage cutoff parameter, but would suspect it to be in the 10-15% range.
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You're right about the ~4.09V at 100% SoC (as reported by HondaLink), but my OBD2 data shows that this is in the range of ~96% true SoC (the OBD2 reports this SoC as "HV battery Cell Max State of Charge" when HondaLink (and the OBD2 "State of Charge") report it as 100%. Presumably this is the SoC of the cell at the highest voltage. The average cell SoC is probably ~95-96%. Looking at plots of NMC battery voltage vs SoC, the 4.09V lies around 95-97%. One could argue that the OCV and reported EV battery voltage when the car is running and reporting OBD2 data is different, but my guess is that the top BMS buffer is pretty small at <5%.

At 10% HondaLink reported SoC, the OBD2 report is in the 19-21% SoC range (~3.53V per cell). At 0% HondaLink SoC it could be around 10% true SoC, but I don't think anyone has ever posted any good data when the EV battery was say <9% SoC, let alone 0%.

These numbers are from OBD2 reports on my 2.5 year old 2018 PHEV when it was at ~20K miles.
 
I think of this whole discussion a little differently. I want my battery degraded so that I can get a new one under warranty and then sell the vehicle.
 
Aaron said:
I think of this whole discussion a little differently. I want my battery degraded so that I can get a new one under warranty and then sell the vehicle
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This strategy has been discussed before...

The flaw in this logic is that Honda will undoubtedly not be providing 'new' batteries when there is a warranty repair. They will provide a replacement that is in-spec and consistent with a vehicle of similar age with typical battery degradation. It is likely they will gather modules from batteries that fail warranty, picking and choosing modules until they get one that is "good enough". There will also not be another full warranty on the replacement battery... They will only continue to honor the original warranty term.
 
MrFixit said:
This strategy has been discussed before...

The flaw in this logic is that Honda will undoubtedly not be providing 'new' batteries when there is a warranty repair. They will provide a replacement that is in-spec and consistent with a vehicle of similar age with typical battery degradation. It is likely they will gather modules from batteries that fail warranty, picking and choosing modules until they get one that is "good enough". There will also not be another full warranty on the replacement battery... They will only continue to honor the original warranty term.
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Is that how most warranty repairs work? They just replace the part with a different part that would be in-spec and consistent with a vehicle of similar age?
 
Aaron said:
Is that how most warranty repairs work? They just replace the part with a different part that would be in-spec and consistent with a vehicle of similar age?
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Not sure you could completely generalize. I am guessing that less complicated parts that are in-stock would be replaced with new parts. This is a very complicated and expensive unit however. They are much more likely to repair / refurbish these than to stock a bunch of new ones that will just sit around on the shelf.

I have no authoritative insight into what Honda will actually do in the event of battery warranty repair, but just repeating previous discussions and this seems much more plausible to me than giving people brand-new batteries.
 
MrFixit said:
Not sure you could completely generalize. I am guessing that less complicated parts that are in-stock would be replaced with new parts. This is a very complicated and expensive unit however. They are much more likely to repair / refurbish these than to stock a bunch of new ones that will just sit around on the shelf.

I have no authoritative insight into what Honda will actually do in the event of battery warranty repair, but just repeating previous discussions and this seems much more plausible to me than giving people brand-new batteries.
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Maybe I will be the test case. When that happy day comes I will let everyone know.
 
Honda has been producing reliable hybrid cars for over 21 years. I purchased a new Insight back in 2000. The cars already come programmed to not be fully charged and control the rate of discharge.

Using HV or HV charge mode up long grade (not sure what would define a long grade) would help with battery temp on a hot day (not sure how hot it would need to be). On a long trip, greater than 50 miles, it would be my suggestion, to let the ICE handle the load of the long grade while slowly charging the battery up the long grade.

Tinted windows, clear tinted front window reflects heat, and when parked the use of sun blockers in the front window will reduce internal temps. You can also use window vents and/or the solar powered window vent fans to help keep interior temps lower. Avoid the black colored claritys.
 
Yeah, I am all for trying to do what I can to prevent degredation, but with the battery being so small, and no ability of the app to stop charging at say 80 or 90%, it's just too difficult to do.
 
Mark W said:
Yeah, I am all for trying to do what I can to prevent degredation, but with the battery being so small, and no ability of the app to stop charging at say 80 or 90%, it's just too difficult to do.
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The car itself limits the max charging of the battery to be below the 100% capacity and limits itself to not drop to 0%. Honda has been designing and using hybrid cars for over 20 years. They know what works. The Clarity has improved cooling of the battery with a liquid cooling system.

"the BMS will only allow charging to ~90%. Target cell voltage is just under 4.1V, which is considered to be ~90% for a 3.7V cell. 100% would be 4.2V.
When you charge to 80%, you’re charging to 80% of 90%, or 72%."

The car handles it all for you. No need to worry about when how or why. Plug in when possible.

On long trips, greater than the battery range, you can select to charge the battery while driving. This allows you to use the EV mode towards the end of the trip. Just requires a little on the fly math to determine when to start charging and when to return to EV only.
 
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