How fast HV without battery capacity decline

But I don't think what qualifies as 'lasting 10 years / 150k miles' is defined. It could have only 50% capacity left and still make it that long. I would not be happy.

 

If you think you will have 300-450,000 miles you will be sorely disappointed.

 

It is 80% of the original capacity in term of engineering. I didn't see it written in stone in the manual but all the miles won't be on the battery. Majority of them will be on the gas engine.

I think most Prius PHV will be good within the warranty period. Using some of the tips provided, I think you'll be able to go way beyond it.

 

I think I'd be more worried if Honda produced this.

I myself have no worries if this runs as well as my current Prius. In all seriousness, Toyota has designed this well including making the battery wide and flat so the battery has more surface area to cool it. I'm more concerned with normal wear like tires and suspension as well as whether the snows I have on my current Prius will fit. Sorry but I believe I have more to worry about the other driver as well as the nut behind the wheel.

 

This was one factor that decided me on buying my Tesla. At 50% battery capacity I'll still have more range than I need. And if the car then takes twice as long to get from 0 to 60, I'll still have all the acceleration I need. (I have no idea whether an old battery, with half its original capacity, will be able to deliver only half the power. But if such is the case, I'll still be fine.)

 

If half the battery capacity is more than enough and battery prices will probably come down, might it not be better to purchase a Tesla with smaller battery capacity now, then replace the battery at a lower cost in the future (if necessary)?

 

I don't know why everyone gets hung up on X% capacity at Y years or Z miles. It is far more likely that a single cell will degrade to the point of failure (high internal resistance) than have all cells degrade uniformly. I don't care if you are talking about a Tesla, Volt, or PHV.

 

Prius PHV has 56 cells. Leaf has 192 cells. Volt has 288 cells. Tesla Roadster has 6,831 cells.

Prius PHV has the least chance of individual cell going wrong. Since the chain is short, the chance of having a weakling in the chain is lower than a very long chain.

The no-plug Prius liftback has 168 cells.

 

Why does the length of the chain change the chance of a weak cell? Also, the cells in a Roadster are in chains of 69, so it isn't that much longer.

 

What I meant was, the more cells you have the higher chance a cell become the weakling. It only takes one.

I have not look at Tesla pack in detail yet. I guess we need to define what a chain is. Is it in series? Would a parallel count?

 

Ignore my comment about chains. I shouldn't have copied the use of that term.

From Wikipedia: "The ESS contains 6,831 [ame="http://en.wikipedia.org/wiki/Lithium_ion_battery"]lithium ion[/ame] cells arranged into 11 "sheets" connected in series; each sheet contains 9 "bricks" connected in series; each "brick" contains 69 cells connected in parallel (11S 9S 69P)"

Anyhow, having fewer cells doesn't make the pack stronger. What matters is how much power/stress is drawn/put on a cell. More cells allow the less power drawn per cell and less stress. A Roadster's battery pack has enough cells that even drawing a large amount of power for its performance does not really stress the cells. I'm not sure about the Leaf, but definitely for PHEVs, the battery is so small that power draw is a concern. In the Prius Plug-in, power draw from the battery is probably limited to limit the stress on such a small pack.

There's also battery chemistry can be tweaked to tradeoff between power density and power output.

 

You are both right.

Fewer cells at the same Wh capacity means each cell is far larger and there is thermal stress and lower power capacity for the pack.

More cells means far higher power capacity for the pack, lower thermal stress, but the odds are higher that a single cell will go bad since there are more of them.

Fewer cells should make balancing the pack easier, but in practice b/c they are built in modules such comparisons don't make sense directly. It would make more sense to compare how many are in the modules most likely.

 

Daniel I think has had an EV longer than the rest of us... So far on my Volt with 4763 miles down I have not noticed any diminished range, or it taking anymore power to charge... As I have been toying with the idea of getting a Leaf and hanging around over there it seems the expected rate of decline in batteries overall is about 1% every 10,000 miles driven... So if my battery capacity only goes down 10% in 10 years I think that would be fantastic as that means I would still be getting between 36 and 39 miles of range out of my Volt 10 years from now. A lot of them are doing their first annual battery inspection, and are getting 12/12 (no battery degradation to report).. So all would seem good for them at least for the first year. GM doesn't give us similar reports, so it is anyones guess there. So far though like I said I am having no issues, and other owners don't seem to be either. It will be years before we even begin to have answer to this question however.

 

Maybe. But the Roadster was built with only one size battery pack. No options for a smaller or larger pack. Someone planning on buying a Model S might use the strategy you suggest. But note that a larger battery pack means less stress on each cell for any given driving pattern. So it might still be useful to have more range than needed, as the lower stress would mean the pack lasts longer.

Darrell ("the EV Nut") has been driving EVs since the EV1 and Rav4EV came out, so he's been driving electric much longer than me. And Allannde got his Xebra the same day (on the same delivery truck) as I got mine, though he no longer has an EV, and last I heard was waiting for a PiP. There are a few other Prius Chat members who have driven electric longer than I have. But I do consider myself an early adopter. I never had a chance to get an EV1. I got my Xebra in May of 2007, and drove it until I got the Tesla in June, 2011.

I read somewhere (though I am not at all sure of this) that the Volt's strategy is to increase the percentage of the battery that is used as the battery degrades, thus maintaining EV range at a cost of non-linear degradation. So you would not see a reduction in range.

As a battery degrades, you would not need more power to charge it. The power to charge would be roughly the same (plus losses) as the power used. Increased resistance with age would not likely be noticeable (IMO). And since the Volt compensates for aging by increasing the SoC range, you should actually see no difference in either range or energy consumed. You'd have to test the cells to see any degradation. Until it's using the full capacity, and then degradation would be rapid.

The Leaf and the Tesla should show reduced range with aging.

My Xebra had no BMS other than a charging balancer. I drove it farther than was good for the original lead-acid AGM batteries, and saw considerable degradation after six months. During the following 3 1/2 years, with the LiFePO4 pack, I did not notice any degradation. (Those batteries can safely be taken to a lower SoC than lead can.)

I expect all the lithium packs in today's mainstream EVs to stand up very well to the effects of age.

 

I have heard that about the volt as well, but I think it is apocryphal. It may be true, but we just don't know.

One thing you are incorrect on though is the power to charge increasing as it ages.

If lithium is lost during intercalation then you don't need more energy to charge. That is what happens when resistance increases with SEI formation. So it really depends on the degradation mechanism of the battery chemistry in question. I have heard in presentations that Mn spinel cells lose >25% of their lithium ions irreversibly when they are first built in the factory. They rate them for capacity after this though so people are not getting ripped off and misled or anything.

 

Read my post again. This is what I said. The power needed to charge the battery is still roughly equal to the power used while driving, plus charging losses. Those charging losses may increase as the battery's internal resistance rises with age, but this should not be significant.

 

Toyota doesn't balance the pack, they balance each module independently unlike Honda which balances the pack. I believe one of the Volt engineers said they also balance each module as does Tesla. As one can guess, Honda prefers smaller battery packs.

 

Hmm. I was figuring on driving the two miles to the freeway, and then keeping it below 62 mph instead of my normal 65. Sounds like I should just go up to 65 and let the car worry about HV vs. EV.

Will that put any EV range back into the battery pack? Or does EV range come only from plugging in?

 

In the case of the PiP, I believe EV range comes only from plugging in. Maybe (?) from regen. But not from the ICE. Once in HV mode, the car works like a regular Prius, where the ICE will charge the "base" portion of the battery, but will not charge the plug-in portion.

Personally, I think this is an unnecessary limitation.