NiMH vs Li-Ion battery - what's the deal?

My understanding is that the throttle mapping curve changed based on steering input in PWR, on the Gen 4, but that was about it - not actually changing engine off strategy or anything. Honestly, when I was test driving the Gen 4, even when getting a bit more spirited with it, I preferred the linearity of Normal (which, on Gen 4, is actually linear).

 

A supporting data point, the EPA.gov "Test Car Database" has columns that rate how well the driver was able to follow the driving profile. It seems "Power" and "Normal" mode followed the profile relatively better than "ECO" mode. This suggests the EPA numbers may be lower than actual for the 2016 Prius.

My thinking is when the test driver trouble follow the test driving protocol, they are likely to make more accelerator changes. A lot of accelerator changes can lead to less efficient vehicle operation. There is an engineering area that addresses process control, how to control a dynamic system to achieve optimum control but humans(*) are not quite so easily automated.

Bob Wilson

* - married about 40 years

 

The sales guy I bought from said that he heard that all Toyota models, including Lexus, will be deleting the spare tires within the next several years. This is in response to the stricter CAFE standards that must be met and added weight lowers mileage. (No other proof other than the conversation. Will be interesting to see what actually develops.)

If you look at the trim base features on the cars with the spare vs the cars without it appears that the deletion of the spare has to do with weight savings. So a smaller lighter battery for trims that have more weight make sense if the car needs to meet the same gov. mileage rating... and if you look at all the models except the Eco in the US they all have the same mileage rating.

Apparently Toyota engineers are really good at squeezing out the weight event in the smallest areas. My P Three doesn't have the roller cargo cover, just the really light weight one. I'll bet the difference in weight between the two is not insignificant. If we look at other tech the weight for all the small bits will add up.

 

I'm skeptical of that theory, because the energy they're taking from the battery will have to be replaced, with conversion losses going both ways. Those losses will be a lot more significant than the deterioration in BSFC at moderately higher engine speed---within limits, of course.

 

Echoing what CR94 said, I agree with bhtooefr's first paragraph and disagree with the second paragraph - it's a driver experience improvement, but it likely comes at the cost of reduced fuel economy.

Optimal fuel economy in a hybrid comes when the gas engine and electric motors are used in their most efficient power bands.

That being said, I think Toyota's tradeoff makes sense - there are plenty of Prius driving characteristics - like the slight amount of drag with the foot off the gas to simulate the drag of a conventional automatic transmission - that trade efficiency for driver feel.

The tradeoffs, if relatively minor - are a great thing -- the more pleasurable the car is to drive by the masses, the greater mass adoption of the Prius will happen. And, now that the Prius is competitively priced, every Prius being sold instead of a less efficient vehicle is a relatively low-cost option for people to help society as a whole conserve resources and decrease pollution. A Prius that was focused "too much" on MPG's (at the expense of driver feel) would not sell as well, would not handle as safely, and would have less of an overall benefit to the planet

 

We're getting a bit off topic, but I've spent the week driving in Germany on Autobahn and round the Nurburgring with my UK-spec gen 4.

There's nothing unusual to report about motorway driving, and I did pretty most of that in Eco mode. On track, I switched to Pwr and gear B for extra engine braking. As you have probably found, the Prius adds more engine braking as you press the brake pedal harder, along with regenerating energy for the battery. This is how we can have titchy brakes that fit under 15in wheels and not overheat them in 12.5 miles of brutal track driving.

However, if you press the brake pedal hard enough, the hybrid system is disengaged, to prevent damage it seems. Fortunately you can scrub off quite a bit of speed without doing this.

The problem you get with track driving on any Toyota hybrid (except maybe the plug-ins) is that after a couple of minutes of hard acceleration there is no battery left to help the petrol engine out, and with the Prius you spend the rest of the time on 99bhp only.

It is not possible to recover enough energy from the brakes to offset the rate of depletion from constant hard acceleration.

Having said that, the Nurburgring was still immense fun. I was not slow at all, would recommend trying the gen 4 on track if you get the chance. Even with 15in wheels, it drives very nicely at track speeds.

Paul.

 

I have seen several references to pricing as to the replacement costs for the new Li-Ion battery in the new Prius. Does anyone have any SOLID pricing on what to expect. Because your battery WILL die at 9 years (mine did) with only 78K miles. I've also seen people underestimate the retail price of replacing the battery in pre-2016 models: The cost estimate with labor which I received from my dealer in Atlanta for replacement of the traction battery in my 2007 Prius is $3700. This cost must be factored into the cost of the car unless at 8 years you plan on scrapping your vehicle down to $1000. Which obviously I'm not doing. My interest is in finding our WHAT figure can we expect to pay (as consumers - that would be at RETAIL + labor) at the 8 year mark to replace the new generation Prius' battery WHEN IT FAILS which it will undeniably do. Any thoughts?

 

When you visit the dealership, got to the service center and ask them for a quote to replace the traction battery for the car you've been looking at. Ask for the part number and price. Then for labor, ask them what the current rate it.

Bob Wilson

 

Not all Prius batteries "will" die at 9 years - there's a lot that are older out there, actually, as far as the NiMH batteries.

Conversely, we don't know the lifespan of the Li-ion batteries in Toyota hybrid applications, as there's only been one other Li-ion Toyota hybrid that I'm aware of, and it's too new (the Prius α/+ - the Japanese and European-market versions of the Prius v respectively).

In any case, looks like list price on the ZVW51 (Gen 4 Li-ion) battery, part G9510-47120, is $4100, plus a $1350 core charge, based on googling around. Add labor as well, although keep in mind that that's a list price, and there's places selling it much cheaper (still with the core charge). For comparison, the ZVW50 (Gen 4 NiMH) battery, part G9510-47130, is the same price, same core charge.

Interestingly, though, based on this, the Li-ion battery is apparently separated into two stack sub-assemblies. Those part numbers don't appear to be available as spare parts, but it may make rebuilding ZVW51 batteries easier?

 

My thoughts are that you like to extrapolate one event into a trend, and use words like "undeniably" when there certainly is reasonable deniability to the situation at hand.

Of course, we're sad to hear of your bad luck.

I put over 130k miles on my 2010, with no signs of issues. I believe that there are many here that have had Priuses for much longer, and have not had to replace their battery.

But, the battery as part of the hybrid system is covered for 10 years, right? (Or is that just in CARB states?) - I know mine (in CT) is covered 10 years / 150,000 miles...

 

Correct...ONLY in the 13 CARB states. Otherwise its 8 years or 100,000 miles.

And the battery will fail....its just a matter of when. I think to be honest with you warranties generally vastly understate the lifespan of parts by a significant margin. The thing is age affects a hybrid traction battery differently than say age affects a well maintained transmission (CVT or otherwise). So I'm kind of thinking if I was expected to drive this car 150,000 miles or more the way I drive (that is 8,000 or so miles a year) I would have been better off with a Corolla. Of course the cost equation is always changing with the price of gas.

 

Unfortunately we really do not have good data on Batt life. Obviously a chunk of Gen2 batts fail in the 7-10 yr mark and some last longer. We do not have the data. Worse in warmer climates. Consumer Reports survey (circa 2013) suggested 3-5% failure on older Gen2's -- which seems low but that's what they got in their reader survey.

We are expecting Li to cost more but lower failure rate, so hard to say cost/benefit ratio. We'll find out in 10 years when the Gen4's start needing replacement batts. Hope I am still around to see the results.

 

Well - everything will fail....it's just a matter of when. Name one mechanical component subject to wear & use that won't fail at some point.

I can tell you that I drove 130,000 miles without battery incident. I have an aunt and uncle with a 2005, over 100,000 miles, the original battery, and no sign of battery issues - yet. If you've been on this site since 2006, I'm sure you've also read that there are many more posts that report no battery incident rather than problems.

It appears, unfortunately, that you've gotten a bad one. That does happen. Some will go 300,000 miles and last for decades, and others will fail early. That's what is known as a "normal distribution".

At 8,000 miles per year, one doesn't select a hybrid for low cost of ownership. There's lots of technologically intense and expensive components that may fail. (However, the odds are against it)

You are correct, a Corolla would have done you better at that rate of driving. Or, perhaps an extended warranty (if they cover Hybrid components - although I seem to recall that the Hybrid battery may have been excluded. I just checked - the battery is excluded, so that plan wouldn't work)

However, at 22,000 miles per year, I can tell you that my 2010 prius was a darned great investment. Gas, oil, and tires. That was it - for 6 years and 130,000 miles. I couldn't be happier, and that was why I'm a repeat customer. And, with an average of just over 60 mpg, the 2016 is a true engineering marvel in my opinion.

Or, you could move to a CARB state... ;-)

 

I think talking just plain miles or years aren't really relevant to the NiMH or LiOH batteries. What is relevant is charge cycles. Each battery is rated at a certain number of charge cycles. Things that affect charge cycles are typically depth of discharge, residual charge during storage, overcharges and temperature of operation. This taken from the Energizer site:

So you can see it really depends on how the miles are driven and for how long each trip takes. I for instance drive 30,000+ miles a year and have almost 80,000 miles in less than three years. Which means I have a lot of miles but not much time and the batteries have been kept nominally charged. It also depends on the individual cells inside the HV battery. You could have 27 cells that are perfect but one cell that's a little low. As so many on here have pointed out, you can often take out the battery pack and test each bank of cells and find the culprit and then replace only that cell. It may not give you much extra time or it may give you several years. It's hard to tell unless each cell has a tiny circuit board that is a smart chip logging history (like laptop batteries have inside them).

 

I hope mine will die at 9 year mark, because i will get a free replacement
Seriously, I'm hoping for at least 12 years, but by then this will be someone else's problem.

Battery enemy number one is HEAT, battery normally heats up because of charge/discharge but combination of high ambient temperature is IMO a tiping pount

 

I've spent a few years dealing with other applications of battery:
-designing & building Quad (copters aka Drones) which use Li+, continuous lifting of 4 propellers consuming 4-8 amps.
-building hi-powered Flashlights (generates 4x amount of car headlight, 5,800 lumen flash light which consumes 7.9 amps at 12volt.

These apps use large amount of power that can only be delivered immediately with Li+ battery.

Also note that there are several types of Li+ compounds used in battery.

In general, Li+ delivers HIGHER power "density" than Ni battery. This means Li+ battery can be SMALLER and thus less weight and space (which are premium for a flying craft), while delivering better and more consistent power. Li+ is also capable of absorbing fast charge current, ie. quicker charge, thus more efficient in capturing power available during braking.
Ni battery won't deliver enough power (current @ voltage) to lift the craft off the ground, so its non-existence in flying craft application is not a surprise.

The enemy of Li+ is heat, but can be mitigated by sufficient heatsink.

Basically, what battery technology do you know that can deliver up to 10amps of current @12v (Drones and Flashlights) and still be light enough to be handheld or airborned (not lead acid battery) ? It's Li+ ion.

the rule of thumb on Quadcopters is that every 80grams of weight will cost you 1 minute of flight time. Thus we struggle to trim weight on those crafts.