Your question is based on the false assumption that the traction battery is EVER allowed to reach 100% SOC. A "full" battery indicator on the dash does not equal 100% SOC.

 

Can anybody else confirm this? I know this is the case with an “empty” battery as the gauge hits about 1/3 capacity once you hit zero ev miles, and this also makes sense given roughly 3 mi/kwh * around 18 kwh is 54mi, leaving a bit extra that the battery won’t consume. On the other hand fully charging the battery leaves you at 100% on the gauge. In addition the whole point of the charge scheduling feature is to have you hit 100% immediately before you leave, minimizing the time the battery is at a full charge.

 

Hello, I can appreciate your question, and hope to share in any information gleaned on your topic. My wife and I picked up our prime XSE on dec 10th, and have charged 4 times since, while the percentage indicator Registers 100% after a full 12 hour overnighted, the estimated EV monitoring the center cluster has only risen to 34-36 miles. I have call in to, Toyota Customer Experience, and waiting for response. Have you, or any others, that might be following, chime-in on their experience on this subjec.
Thanks for this community!

 

It only provides an estimate based on your prior driving habits. If you are heavy on the gas your mileage will go down, or if you use temperature control, also how fast you go etc. based on all that it estimates how far it thinks you can go based on your current state of charge. If you do low speed and easy on the gas, the numbers will go up but it might take some time. Mines around 51 miles at full charge now.

 

Here are my traction battery capacity observations w OBDII ScanGauge II:

• Full Charge State Of Charge (SOC) observed at and around %90.5
• Implying just under %10 upper traction battery buffer (less than 1.81 kW)
• Empty Charge at SOC %13.7
  Implying that ICE turns on when battery still has 2.48 kW or more. I intentionally tried to trigger ICE on as late as possible, by driving the last mile very slowly (residential) and without any obvious energy draws (AC, music, fan)
• Full/Empty SOC imply maximum 13.81 kW EV (non-emergency?) traction battery capacity.

Here is a thread about low initial EV miles with Rav4 Prime (R4P); Why does it take a while for a R4P to get up to its full...
Just remember that EV range is a running average and it was not run efficiently in the few miles it took to set-up, test, and get to you.

 

I'm not at all worried about charging our RAV4 Prime to full every night. I'm keeping careful stats on charging vs. all-electric mileage vs. temperature, so I should be able to see over time how much degradation there is in the battery pack; I'm expecting normal, very slow degradation in the battery pack over years.

 

You used to be able to reset the EV miles (driving estimate) by disconnecting the 12v battery, and the estimate would go back to the preset official numbers. I have not tested this on my R4P. My R4P was our first Toyota hybrid vehicle (of 5) that came delivered with a low EV mile estimate that took more time to average up.

The good news is that it did indeed consider/average my good driving efficiency and within 2 weeks (kind of slow) the EV Miles were over 40, max of 48 in summer, and after winter cold averaging EV down I still see +40 EV Miles (NO AC). I only GET those 40 EV miles if I’m driving with no AC, and under 55 MPG when it is near freezing. Over the years I have noticed that new owners forget the significant impact (on ICE and EV) that cold weather has on EV miles estimate. As winter sets in I always see new owners searching for answers for lower EV miles. You can “just drive it” and wait until warming weather. Or you can drive around in your cold cabin with seat/steering wheel hat but no AC and hope that you can get some air on the windshield so it does not fog up. Been there done that at times on most of our Toyota Hybrid vehicles.

Back to thread topic;
Here is how I would limit R4P charging. Figure out how to use set Charging to Departure time and set the departure time to target (3/4?) of full charging time, based on volts/amps from car charger. If you don’t set a day for your charge schedule it will be carried out once.

Chazz was here

 

 

I was thinking you would estimate how long for full charge and set departure time to shut recharging down when SOC at target value (approx). I’m sure we’ll come up with other options.

After 5 family Toyota Hybrids I have come to trust the Toyota engineers to take into account common practice of plugging it in when you get home and don’t care if it sits days with full charge. They stand by the battery and charger equipment for 10 years or 150,000 miles (increased from 8yr/100,000mi for 2020 vehicles). I have found this passage from the Owner’s manual (Page 84) to lessen such worries;

■ If the vehicle is not used for a long time
●The 12-volt battery may dis- charge. In this event, charge the 12-volt battery. (P.539)
In order to prevent the hybrid bat- tery (traction battery) from becom- ing extremely low in charge, charge the hybrid battery (traction battery) from external power source or start the hybrid system at least once every 2 or 3 months, and turn the power switch off after the gasoline engine has stopped automatically. (If the gasoline engine does not start up even after approximately 10 seconds have passed since the “READY” indicator came on, the power switch can be turned to off without any further action.) When the 12-volt battery is dis- charged, refer to P.539, “If the 12- volt battery is discharged” and perform the correction procedure.
●When the vehicle is left with the AC charging cable connected, the electricity consumption amount of the 12-volt battery increases due to controls, such as the system checking, operating. When the AC charging cable is not needed, immediately remove it from the vehicle.

So under the heading of “if the vehicle is not used for a long time” they mention “2 or 3 months” as a time frame. Second bullet recommends immediately remove AC charging cable when not needed. This has been sited to mean any time the AC charger is connected and not charging must be avoided at the cost of timing charge completing to most/all departure times. But I think because it in under the heading of “... for a long time” it only applies to a vehicle sitting for a long time.

My wife has been been plugging her Prius Prime every time she parks it in the garage, but we will have to wait 5 more years to see if the battery/charger becomes un-usable within the warranty period.

 

I agree with Chazz8's comments with one exception. We have owned 2 Prius Primes for 3+ years and have experienced the exact Guess O Meter experiences as the R4P when new. The PP's took time to learn driver performance/behavior over months, the DTE EV on the GOM kept going up. In summer routinely gets 35-37 and in winter, now 32 which is expected. Our R4P is currently up to 48 today, and remember, it's a guesstimate, and we are very conservative drivers at mostly low speeds. Turn on the AC and it drops 2 miles immediately.

 

What I'm doing: I've purchased a short outdoor smart plug extension cord rated for 15 amps that the charger plugs into. I check the charge level by EV mile range when getting out of the car (but I should be able to check this on my phone!!!) and plug in the Rav. Then I use the charger app on my phone to set a timer for when the charger should turn off, assuming 3.5 miles charge per hour. I made a table so I don't have to do all the math each time. My prelim charge is to 30 miles (~70% full = highest happy battery charge from my reading), then I can charge more the next day just before leaving if I know I've got extra driving to do.

 

can you link to the extension cord you are using?

I am happy to trust the Toyota engineers. But is such a simple setting to add - and it might help owners preserve their batteries, preventing future headaches for Toyota - so I am puzzled as to why they didn't include it.

 

The manual does imply in some places that you should time charging so that you use the car not much after it completes charging

 

The OpenEVSE level 2 charger has WiFi capability that optionally lets you select how many KWH to charge. If you're around zero charge, it will take around 15 KWH to get to full. So for example, you could tell the OpenEVSE to charge up to 13 KWH, then shut off.

 

My charging pattern is very much influenced by this, from here. I don't think these differences are "just splitting hairs."

 

My charging pattern is very much influenced by this, from here. I don't think these differences are "just splitting hairs."
View attachment 174777

Very interesting to note the inflection points on each graph: cycles per day/ /Time at SOCmax /and average temperature that are all dependant on Depth of Discharge (DOD) and how, after that inflection, the lines converge. Each inflection point moves to the right for each parameter at a less ideal state. Ideally one would keep the DOD below 70% and end up with very long life for your battery.

If you look at the results of each of these graphs it looks like Toyota designed the RAV 4 to optimize for this data (eg 42 mile range = 1 charge per day; or 90% SOCmax.)

 

As a Chevy Volt owner, I've noticed a very slight rundown in battery capacity over the 6 years I've owned it. The first Volts came out in 2011 and I follow the Volt forums closely. There are very few, if any, complaints of battery capacity degradation even 10 years later - and the vast majority of Volt owners just charge their batteries fully whenever they can.

As I understand it, the explanation is that proper battery management (especially temperature control) is far more important to maintaining battery longevity than keeping the state of charge at well under 100%. Possibly, as these cars age more, that will change - but for at least 10 years I don't think we have much to worry about if Toyota was as diligent with their battery management design as GM.

 

I read somewhere (can look it up but not right now, reasonably reliable source) that battery is happiest between
35 to 70% full. So I use 70% as my target initial charge, hold there, and then finish up before travel. It gives me a car that is always primed with enough miles to zip around town for errands if something pops up. Re charging times, I think even the 6.6kW charger using level 2 is still considered "slow." Fast is like Tesla DC rapid charging. So I don't worry about 8 vs 16 and just plug it in. I have an SE so it takes hours no matter what.

 

I think we're close enough to...good enough...to easily have the battery outlast its 10y warranty and perhaps me as well! As we charge maybe 4x/week the battery is often right in that 35-70% SOC while the car is at rest. I would have to guess the relationship on rate of charge is somewhat linear in that if 2h is 'slow', then 12h must be slower than molasses in Alaska in January! Anyway, thanks for your insights and I will continue to consider it mostly academic and won't change habits it's just not going to be worth it for us.

 

What I've read is that for longer battery life: lower DOD is better than higher DOD, lower charge and discharge rates (C rate) are better than higher, lower temperature (within limits) is better than higher temperature and lower SOC (but not too low) is better than higher SOC.

How much these parameters affect the battery and what constitutes high or low in each case probably varies quite a bit by battery type, manufacturer, etc. In short, there are a lot of variables and many of them aren't available to the average user. Finally, the NREL documents that I read and that looked a lot like the plots above, were several years old.

Battery tech is changing very fast right now and 2021 batteries are probably quite a bit different than 2015 or even 2018 batteries. For example, the batteries in Nissan Leafs seem to do better every year. The ones from 2011-2012 failed miserably in a few years in hot climates. The ones from more recent cars (2020+) seem to be holding up extremely well, even in Phoenix, AZ. There has been a steady trend evident between those 2 points with the batteries doing better every year. Within those general trends, there is quite a bit of variation due to unknown properties. The Leaf reports the 'state of health' of the battery through its OBDII port so there is a far amount of data available for those that care about and track this type of stuff. The trends are undeniable and very significant.

A 2021 Leaf battery can have measured degradation rates 5x or more better than 2011 models as measured by the reported state of health, which usually tracks well with measured real life range. That much is easy to measure. Why that happened or what parameters affect the degradation are subject to a lot of guesswork (and argument) on Leaf forums but the bottom line is that no one really knows since no one has the means to subject identical cars to different conditions to measure the effects. NREL has done that, but it is with batteries from several generations ago.

 

Toyota already limits the charge to 90% and can increase or reduce it by the computer. But it but it is not in your control.