Is Immediate Charging Wise?

i would say don't charge. does the manual say not to leave it at the lowest possible charge?

 

I think the dire warnings about not leaving the car in a mostly discharged state is for the situation where you won't be using the car for some extended period of time. Like for at least a month or two. If I were to encounter such a situation (3 HV battery bars, long trip coming, just got home), I might be inclined to plug the car in for an hour or so to get a partial charge into it, but not necessarily a full one. In a likelihood, I'd just park the car and leave it.

I have only managed to run the HV battery indicator down to 4 bars, and that took some work. Most of the time it bounces between 6 and 8. In my 2005 Prius, I would regularly bounce between 2 and 7 bars. I have a hill that I have to climb up every day I go to work. I have been up this same hill over a thousand times. Sometimes when I would get to the top of the hill, I would be at 2 or 3 battery bars. And other times it would be at 5 or 6. I could never figure out why since this happened in all sorts of different weather conditions. Nowadays when I go up that hill, I'm either in EV mode with ICE blending, or I deliberately put it into HV mode for the climb. Depends upon my mood.

I suspect the dire warnings about not leaving the car discharged for a long time won't apply to normal day to day use of the car. Rather they are for those rare outlier situations that most of us will never encounter.

 

Where did you see Toyota recommending principle #1? I think the two relevant points from the Owner's Manual pg. 93 are:

I believe the first point applies to leaving the car undriven for a few days. The second indicates the car should be charged just before driving, not not charged after driving.

 

I used to think the same as iRun.. in fact, I'm sure I've said it here a few times (when discussing my charging "strategy" and how I wanted to let the battery "rest").

I do believe it was based on the interpretation of the two points you highlighted from page 93. I do also recall someone mentioning something about not charging a hot or warm battery or something to that effect. Put those all together and the idea of letting a battery rest came to be (or at least thats how I see it).

HOWEVER.. I was driving down a relatively steep hill a few days ago. I had used HV to "climb" the hill and at the top, switched over to EV. On the way down the hill (took maybe a minute or so at 50-55MPH), I picked up 2 miles of EV range from regeneration. Now, that got me thinking about the "battery resting" thing.. with regen, you're constantly charging up your battery. And you're doing it at a rate that is much faster than even charging on a Level 2 charger.

So I agree with Joseph. I think the idea that has been tossed around that the battery needs to rest is incorrect.

 

With lead-acid, you would never want to wait before putting it on a charger.

Lithium batteries are much happier if kept at 40%-50% SoC in general, so they would perhaps prefer that you follow the guidelines from P. 93. It has nothing to do with a rest period.

I don't know that Toyota engineers necessarily foresaw the use pattern of racking up significant EV miles with regen.

 

I think they designed it that way. The terrific regen rate may be a larger benefit than the plug-in charge!

 

I charge immediately if I know or suspect I will be going out again soon. If not, I set the timer and let the car get charged just before next commute. I get the EV range down to under 1.0 on both legs of commute so I have a lot of full discharge/delayed timer recharges such that I don't worry about battery health, even though the nights and weekends have a lot of partial discharge/recharge cycles.

I will say, however that having a 150k warranty on such new tech is reassuring!

 

Oh Andy my friend . Unless you are coming off Donner Pass, just plug it in and deplete those EV miles to zero, then drive it like a normal Prius. High rate charging i.e. sustained regen is detrimental to battery life, particularly when the state of charge is already high. And as far as I can tell, the people who are playing HV/EV games to add back in EV miles with regen are getting lower fuel economy and they could be causing pack damage in the long run.

 

TY Seilerts. I will defer to your overall Prius knowledge and yes I do come back from Reno several times a year.