2021 Plug-In Battery Question

This raises an issue I’ve thought about before when hearing that we shouldn’t let it sit with 100% charge. Isn’t it the case that it would really only be at about 80% charge given the built-in buffer? This would then mean that it wouldn’t be sitting full even after a full charge?

 

Don't worry about it. Too high or too low of a state of charge really only has a big impact on Li-ion health when it comes to storage. If you are regularly using the car, then just charge it whenever you can.

I believe the manual warning CYA for rare worse case scenarios. Parked in a high heat climate. With the PP's minimal battery cooling, Toyota lawyers likely were worried about a Leaf incidence.

 

From my small number of use cases, the practice of charging did not alter the traction battery degradation rate noticeably by changing the routine.

• For my 2017 PP, I used all traction battery charges on daily bases and charged it fully at night using the battery charge schedule for ~3 years.
• For my 2020 PP, the car was almost never charged full, and mostly sat on the driveway with 30-40% charge left on the traction battery, and when being charged, it was charged only to ~50% unless I planned to use it up the next day. I did this ~10 mo.
  
• For my current 21 PP, I charge whenever convenient either when the traction battery is empty or partial charge remained, and charge it to full most of the time even if the car is not going to be used for a few days. I have done this for 15 mo now.

In all three use cases, the traction battery rate of degradation was similar during the first year of usage, which was at about a 5% loss of capacity in all three use cases.

I reported my data in the linked thread below. See the graph for a comparison of three different PPs having received different charging routines.

2021 Prius Prime traction battery: the first year degradation

 

An argument could be made that only pure electric vehicles should be using public charging stations?

Or is that heresy lol?

 

Or conversely, pure BEVs should not park at certain public stations (ie: shopping centers, city halls, libraries) for prolonged periods of time. We've seen BEVs hunkered down for the long haul (all day or overnight) at spots provided for shorter term shoppers etc.

A better solution coming into use here is via Chargepoint stations at which you log in and are provided one or two hours of subsidized (FREE!) use by the facility, after which time you are billed to your CP account.

 

That's tragedy of the commons, and occurs because those chargers are free. When users have to pay, their behavior changes. For the inverse problem, chargers are now applying parking or idle fees to cars that are done charging.

That is the Volta network's entire business plan, plus the chargers being used as ad space. Pretty sure with Volta the free use limit is tied to the entire network. The user agreement also has language that lets them start charging fees to abusers of the system.

 

Yes, there is. The ideal battery state-of-charge (SOC) for storage is about 20–30% on the multifunction display (30–40% actual SOC) for the Prius Prime. High SOC levels are especially detrimental on the battery life. Therefore, to extend battery life, you should charge just before you drive or use the scheduled-charge feature.

However, it makes no difference whether you charge a depleted battery or a half-charged battery because lithium-ion batteries do not have a memory effect. The only thing that matters is what SOC you store the battery at.

PS: The owners' manual erroneously states that the car should be stored with a depleted battery when the internal-combustion engine kicks in. This seems to be written with the non-plug-in Prius in mind, where they instruct the internal-combustion to kick in before they store the car so that the non-plug-in hybrid-vehicle battery is not stored at near 100% SOC, which is detrimental to its life.

 

Sorry, can’t understand that. Who is “they”, for starters? And don’t see how I’d get the state of charge at some level, when getting home; doesn’t seem practical or doable. Where in the owners manual is this?

 

The SOC for the non-plug-in Prius will vary between ~ 10–100%. What the owners manual says (I think it also says in yours) is to wait until the ICE kicks in before you store the car. This will ensure that you are not storing the car with at near 100% SOC on the non-plug-in-hybrid battery, which would reduce its lifespan.

 

Where did that SOC info come from?

 

From Prius Prime.

 

If it's the display value, it likely isn't incorporating the top buffer.

 

No, the actual value read by apps.

This is a moot issue. The point is that you don't want to store a lithium-ion battery in a charged or discharged state. The ideal storage SOC is ~ 30–40% actual (~ 20–30% on the Prius Prime MFD). For that reason, it is a good idea to store a non-plug-in hybrid by turning it off when the ICE just kicks in while in the EV mode.

 

Just to be clear, the warning about the capacity reduction of the hybrid battery and recommendation to leave the traction battery level low during a long storage period is very specific to Prius Prime and also for previous plug-in Prius. The same warning also appeared in the Pip owner's manual. But you will not find similar wording of recommendation in the owner's manuals of regular Prius. The section containing this clause for PP and Pip is under "Charging" which does not apply to non-plug-in Prius. Therefore, it is very unlikely that the recommendation was intended for the regular HEV Prius and erroneously printed in the PP and Pip owner manuals. The clause appears in every year's models of Pip and PP, thus it is very unlikely they are just a simple error in printing.

From Prius Prime Owner's Manual


From Pip owner's manual


EDIT: I also checked the owner's manuals of Rav4 Prime, Rav4 EV, and Rav4 Hybrid. The exact same clause "Leaving a low level of charge..." appears ONLY in the Rav4 Prime, not in the Rav4 Hybrid or older Rav4 EV, indicating Toyota's intention to include this recommendation specifically for the PHEV, not for an HEV or a BEV.

From Rav4Prime owner's manual

 

Obviously, a high SOC is a lot more detrimental to the lithium-ion battery than a low SOC (as long as it is not below ~ 5% (actual SOC, not MFD SOC), which could also also be pretty bad). Toyota seems to be trying to caution owners from storing with a high SOC.

There was also a report here of a fairly new Prius Prime suffering battery failure or severe capacity loss because it had never been charged.

None of this discussion changes the fact that the ideal storage SOC for a lithium-ion battery is 30–40% (20–30% on Prius Prime MFD), and owners should try to keep the SOC close to that range when the vehicle is not driven. Certainly, extremes such as 100% are the worst, but 0% on MFD is around 10% actual, which is not too far off from the 30–40% ideal actual SOC for storage.

 

While I see points made by many for the best practice to prolong the longevity of the traction battery, my own experience and data point to the indifference for the rate of traction battery degradation for the short term (less than three years) regardless of the way the traction battery is charged.

There may be some statistically significant differences in the rate of degradation if compared for a long term say for 10 years. But I am not going to be overly concerned about how I charge the traction battery on my PP. Yeah, I am not going to charge it up to 100% and store it under the hot sun for months at a time. But for my current normal usage of several unscheduled trips per week, mostly 15-30 miles EV range trips, I just plug the car when it is convenient, so the car has a full charge when I need to use it. If it sit for a few days with 100% SOC on the dash, I am not going to panic. My data clearly shows at least for the first year, the rate of degradation is very similar to my previous PP which was almost never charged to full but sat mostly at 30-40% SOC.

Here is the graph of similar data taken from my other two PPs. 2017 PP was kept for 30 months, and 2020 PP was kept for only 10 months. The 2020 PP (Red bars) shows a very similar rate for the decreasing kWh for a full charge for the first 10 months as the 2021 PP (Green bars). Unfortunately, I did not keep the record for the 2017 PP (Blue bars) between months 5-16. But after 24 months, the 2017 PP full charge kWh number is similar to 12 mo old 2021 PP data.

 

What is the reason for switching to HV from EV mode on a Prime prior to powering off prior to storage as per the manual?


iPhone ?