Plug-in best charging strategy

I agree. Battery management will take care of it. I was just suggesting for the request of the OP wanting to squeeze extra life out of the battery. It does require planning and compromises a bit of "readiness" to use it but the timer makes it easy.

 

The battery isn't actually at full charge though. Letting it cool is likely the main reason.

Also, all battery chemistries discharge to some degree. The charger will keep it topped off. I would guess it would use more electricity doing so than a timer, but, except for the truly anal, I wouldn't worry about it.

A relevant question, does the basic charger, or non advance trim, have a built in timer? The Volt charger warns to just plug it directly into the outlet. When plugged into a gang plug, power meter, etc there have been reports of melting and scorching. The Prius doesn't draw for as long, but it is drawing a lot more than a table lamp.

 

As has been noted by others, lithium batteries have no memory effect. Nor do NiMH batteries. NiCad were the ones that had this.

The batteries themselves have no chip. Charging and discharging is controlled by the car's computer and BMS (battery management system).

I've never heard of a car that used the cells one after another. The BMS will monitor individual cells for health, and in some cars the BMS can remove unhealthy cells from the circuit, thus protecting the rest of the pack. But the entire pack (minus any damaged cells that have been isolated) will be used all at once.

Although my Tesla uses a different lithium chemistry than the PiP, it's worth noting that the owner's manual recommends putting the charger program on "Storage" if the car will not be driven for two weeks or more. In this mode the pack is kept at 1/3 to 1/2 charge. Being "fully" charged (actually 90% in Standard mode) for a few extra hours makes no difference at all. I set the timer to charge at midnight. This gives the pack some time to cool and uses off-peak electricity, even though I don't get an off-peak rate.

 

The first place to check for that will be the owners manual. The answer may well be in there.

 

My local utility (So Cal Edison) offers a lower rate for charging the PiP between midnight and 6 am. That's on a single residential meter, but with the "home and electric vehicle plan." If I have them install a second meter free, it will be for the car only, and lowest rates are for 9 pm to noon. But in order to have that free second meter, I have to have an electrician prep the existing panel or put in a new one, at a cost yet to be determined, so it may not be worth it.
(Your rates may vary.)

 

It would not necessarily believe this entirely if I were you. There is a certain amount of potential energy in a cell as you charge it that amount increases. The higher voltage means there are a wider variety of side reactions that can occur as well. This implies keeping the battery at around 85% state of charge might actually be better for the battery. All of this is mainly nonsense though because we are not talking about phones and laptops. Not only are the cells in the battery different, but the charge in the Prius one assumes will actually take care of the battery as well. The user should not have to be fiddling about like this trying to figure out how to make it work well. Go read the nissan leaf warranty book and what it suggests to prolong the life of the battery.

They don't want people to recharge till it is below 80% b/c holding up at high voltage will wear it out. So will deep discharges, but the vehicles will not allow that. A user could discharge the battery and then leave the car sitting a long time which has the potential to damage it, but that would be an unusual circumstance.

 

I wonder how much of the advice for the Nissan Leaf charging will be applicable to the Plug-in Prius. I certainly will be reading and following my PiP owner's manual first!

 

I agree with you!

With BEVs like the Leaf, one must depend on the remaining charge to get home. With the PiP we can run down the battery and still drive home on the ICE. This will mean that our driving habits and charging habits will be different and perhaps not as careful.

The key issue here is finding and keeping the "sweet spot" for the battery. Batteries last much longer when you do. This "sweet spot" is somewhere between 50% state of charge and 85% state of charge. In the real world, we just will not be able to outsmart the battery management system. It will try hard to keep us out of trouble. If we simply plug in when we can, as often as we can, we will probably be fine.

 

i doubt if Toyota left it up to you to decide how best to charge your pack. guessing that the highest SOC you can get is probably 95% and the lowest probably around 15%. so my recommendation; charge it up as much as you can as often as you can.

for your cellphone; its not good to leave LiIon fully charged for extended periods of time. as far as short duration charging sessions, i have not heard any detrimental things about doing that and that is a relatively common practice with high demand smartphones and car chargers. but cellphone batteries are $40 and they are designed to charge to 100% to sacrifice a little longevity for capacity.

for a multi thousand $$ car battery; its a completely different story

 

Not to mention the cell phone needs to last 2 years for most people. Not so with a car. I think you are wrong though. I highly doubt that Toyota will allow 95-15% swing. I will be quite surprised, but not upset by such a decision.

 

I'm going to put a lot of faith in Toyota's battery managment software/system. I can't imagine that they are leaving much to chance (relying on the user to do the 'right thing').

Did Volt or Leaf have as many prototypes (pre-production) units out with ordinary drivers like the 2010 Prius PHV did? I doubt it. I bet the Toyota engineers got to see at a lot of battery scenarios and patterns from that data. Good battery managment is a key part of a PHV design's and I hope they got it right (I'm essentially betting my hard earned money on it with my PiP purchase).

 

cell phone batteries are rated at "300-500" charge cycles which means 2 years?? good luck on that!!

as far as what they charge cycle is on the PiP is it not "100" (or whatever it really is) to 30%? or something like that?

i guess what we need to know is what is worse, charging to high or discharging too low?

charging too high and leaving it fully charged for extended periods of time the voltage tends to break down the components needed to transfer the charge but at the same time you want as full a charge as you can get so you get make it there and back without the "white knuckle" effect setting in.

now as i understand it, you can discharge relatively low as compared to other battery types and it is not detrimental to leave it as such. optimum SOC for storage over more than a few days for LI is 40% SOC.

so it all becomes a balance of longevity verses utility. now we have a half dozen major plug providers who all seem to have slightly different strategies for pack management.

who will be right?

Nissan who is allowing probably about 80% of the battery capacity to be accessed? that is why i threw out the 95-15 #'s.

or the Volt which is allowing much less but does not seem to want to provide more of a guarantee of battery longevity?

its all interesting and i am sure each manufacturer is somewhat confident of what they are doing.

Nissan is taking the biggest gamble by far in many ways. they were on the brink of bankruptcy only a short time ago and to now put as much as they have into the Leaf, they are literally betting the company on the Leaf being a long term success.

last week, i did a "cold weather" range test of my Leaf. i drove only around town. did the trip on a single charge and drove 100.1 miles averaging 5.3 miles per Kwh with temps running from upper 30's to mid 40's. real world driving it most definitely was not and it included padding the mileage for the last 8 miles or so (was not gonna pass up the chance to go 100 miles in winter!)

normally the Leaf provides access to about 21 of the 24 Kwh in the pack but that is measured at 68º (i think...around there...or maybe i am confusing STP for gases?) so the colder it gets the less able the pack to take a charge. so generally in my area we are seeing access of around 19 Kwh.

but on my drive i used 98.5 to 2.5 % or 96% of the available charge per 3rd party installed SOC meter but as you can see, what is touted as 100% is actually less behind the scenes.

 

Boy, that is quite a range of possibilities.

Can they all be right? I am not betting on it but would be more than pleased if that is how it comes out.

I would never do what you are doing with the Leaf, stretching the miles. You may be fine, but you may also pay dearly for asking so much of that battery. It is impressive that Nissan is betting so much on the battery and they will win big if they prove correct just as Toyota has with the Prius. And if they are wrong, well, we know what will happen.

I am betting on Toyota's more cautious approach. With the PHV there is no need to press the battery so hard. It uses a little petrol which requires a compromise that some prefer not to make, but it is a solution which may have long life after all.

We live in interesting times.

 

I only did the test to create a baseline. There is no other real way to determine range degradation.

My normal driving is about 25~40 miles a day. I rarely charge to 100% so think iwill be fine