How to turn a Prius into a Plug-in hybrid

[Gary Allan]

That's baloney too. You forgot to mention that the CVT transmission in a Prius has about eight moving parts (look at the diagram for a simple planetary gear set) versus the hundreds of moving parts found in a contemporary multi-speed auto.

Perhaps, but have it fail and I assure you that it will challenge a much more complicated transmission in repair cost. Just my speculation/suspicion

Oh yeah, I forgot to add that the HSD cars also have NO ALTERNATOR at all, and NO STARTER MOTOR at all, so this statement is just plain FALSE. Gee, never seen a GM car drop a starter or alternator...

True, but when your version of the starter/alternator goes bad, I'd venture to say that the labor and parts bill will equal several lifetimes in a few GM vehicles in comparative costs. Again, just my suspicion/speculation. Way too little distribution and one vehicle throughput in terms of parts. You would probably compete with the assembly line for parts

Before I bought mine, I walked over to the parts department and got a quote for a new traction battery -- $2,300, (two thousand, three hundred dollars) period.

That was then. Now do it with the demand for the hybrid on the incline. Let alone inflation and whatnot. These won't get cheaper as more units hit the pavement.

Not having the ability to plug this thing is in a serious oversight, imho.

 

[swalve]

Originally Posted By: ekpolk
the ECU is very "strict" in never allowing the traction battery to go above 80% or below 40% SoC.


I've seen that before- I'd never heard that fully charging a battery causes failures and loss of lifespan? I'm not arguing, I'm just curious. Is that some kind of optimization thing they did for longevity? IE, if the "right sized" battery would last 5 years, does making it 20% larger and charging it to 80% make it last 10 years? (At least, with the particular battery chemistry they use.)

Originally Posted By: ffracer
The solution is to use capacitors to extend the cycle life, but there is a long ways to go.


Are you talking about using a very high capacity capacitor to quickly accept the charge, and then metering its output to optimally charge the storage battery? I like that idea- I think I read something about that on Slashdot to create cell phones and iPods that only take a matter of minutes to charge up.

I would imagine that it would take a lot of safety devices to have a car running around with a bank of capacitors on it.

Originally Posted By: ffracer
Don't believe the hype about Lithium ion batteries that are used in phones, laptops. They have a long ways to go also.

Eventually the two will come together and this will a break through.


That's true- Lithium Ion seems to have a fairly strict life span- I believe I've heard something like five years from the time the cells are manufactured. And their ability to discharge quickly requires electronics and fusing that causes the cells to "commit suicide" if they sense a too-fast discharge. I'm dealing with some combination of that at work- some IBM Thinkpad batteries are dying at around one year of use. Combine that with the Dell batteries that were "exploding", and you can see that we're still learning about how to best use the LiIon batteries.

As an aside, the Energizer Lithium single use batteries are awesome- I have a digital camera that would just eat batteries like there's no tomorrow. Turns out, it just draws too much current for an alkaline to handle. Even though the Lithium ones cost 2-3 times more than alkaline, they more than pay for themselves by lasting at least 5x longer. And in addition, after the camera calls them dead, they still have plenty of juice to use in remote controls and pocket flashlights.

Originally Posted By: ffracer
Don't assume it will be low performance either.


I can't wait for the electric muscle car to take hold. People will wonder why anyone ever did anything different- the torque of electric motors is tremendous. I've already read that there's a electric racing association doing something with it. I saw where they have batteries with drainable electrolyte. After running a race (quarter mile, I think), they drain the spent electrolyte and pump in charged up electrolyte and it's ready to go again.

These guys, for example:
http://www.nedra.com/about_us.html

 

[swalve]

Originally Posted By: Gary Allan
That's baloney too. You forgot to mention that the CVT transmission in a Prius has about eight moving parts (look at the diagram for a simple planetary gear set) versus the hundreds of moving parts found in a contemporary multi-speed auto.

Perhaps, but have it fail and I assure you that it will challenge a much more complicated transmission in repair cost. Just my speculation/suspicion


I think I got this link from this forum somewhere...
http://www.artsautomotive.com/PriusMG2.htm

The Prius transmission *is* complicated, but partially because people aren't familiar with it yet. Yet it's a beautiful piece of engineering in its simplicity. It uses a concept similar to a differential in a rear wheel drive. Picture how one works- the drive shaft turns and spins the wheels. If one wheel locks up, the other wheel spins twice as fast. In effect what they did was hook two motors and the gas engine up in a series of "differentials". Depending on the speed required, they modulate which motor is doing what to create the output speed necessary. During slow operation, one electric motor turns and the others are locked. Then the next electric motor begins spinning, multiplying the speed of the first. When it's up to speed, the ICE engine kicks in and the motors lock. When it needs even more power, it uses a electric motor to add force to the system. When it is time to generate, it unlocks the motors and uses them to absorb energy and charge the batteries.

Or, what these guys say:

http://en.wikipedia.org/wiki/Hybrid_Synergy_Drive

http://www.toyota.co.jp/en/tech/environment/hsd/pdf/a_guide_to_hsd.pdf

 

[glennc]

The fundamental problem with making the Prius a plug-in appears to be the battery capacity. It would be an impractical plug-in with the current capacity, taking from what ekpolk has said, but to give it that much more capacity would require far more cost and engineering compromises than what were required to make it what it is. It sounds to me as though they made it exactly what it should be, and its popularity, its efficiency, and its apparent reliability are testament to Toyota having done excellent development work.

A plug-in hybrid is still a great idea and, I imagine, the next major step in technology. Chevy Volt?

 

[Gary Allan]

Well the way they do it is fine for just about everybody. But suppose you're in a situation where you can run entirely on battery power and never breach the 80-40% charge? That is, the IC need not run ...EVER (during your routine usage). You don't have that option. Now I guess you could just buy an electric golf cart ..but that you can't change your mind and take a 300 mile trip with at the same time.

 

[ffracer]

Yep, I was talking about capacitors for buffers.

The problem is that plug-ins rarely will run on no ICE and stay in the window for state of charge. They make the Euro and Japan Prius models with this override and it rarely is useful enough.

Also, the battery warranty in those markets is only 5 years, vs. 8 in the USA/Canada. Hence, the difference.

Going down to 40% state of charge regularly does affect cycle life. There's no free lunch.

I talked to Toyota's head of hybrids and they are well aware of the interest and tradeoffs and are working on it heavily, as is GM and others.

GM has some pretty impressive hybrid tech, just most of it has not reached the consumer models.

I drove a Honda FCX with all capacitors and no battery. It was very impressive for a city car. Cannot be used on the highway, but needs very little charging in city use.

 

[Bill in Utah]

I love that this guy spent $25k for a Prius (got no problem with that) THEN spent another $32k

to save 12 cents a mile (normal Prius is 14cents, his 2 cents)

He will make his $32k back in only 266,666 miles. (if he did not invest it anywhere...)

Pass. Plus he is banking that his electric rate stays the same for those 266k (yeah right)

Or if the batteries last that long....

I don't get it.

Don't mess with a good thing. Let Toyota figure it out. (It will cost less than $25k +$32K in the end)

Bill

 

[Bill in Utah]

Reading the article I saw this...

Quote:
To maximize the chances that the standard Prius battery pack will survive 10 years under any conceivable operating conditions, Toyota rigorously keeps the pack’s state of charge—expressed as a percentage of the full-capacity charge—between 50 and 80 percent. Toyota does not disclose exact details, but some engineers say the band is even narrower under most operating circumstances.


So, when you are going down the freeway (my big problem when I've been in a Prius) and we come to a grade, the engine just has to scream up the grade, is it because the battery will not be allowed to help?

Or let me ask this, *if* they allowed the batteries to go lower could it help going up grades and such?

Just wondering.. Bill

 

[ekpolk]

Originally Posted By: swalve
...
The Prius transmission *is* complicated, but partially because people aren't familiar with it yet. Yet it's a beautiful piece of engineering in its simplicity. ...


Yes and no. What I meant is that compared to contemporary multi-speed autos, it's not complicated at all. So yes, it is very elegant in it's simplicity and ingenuity. It's really just a simple planetary gearset. AND as I stated previously, it has far fewer moving parts. The center shaft is connected to the smaller of the two motor-generators (MG1). The ring in the middle, which carries the planet gears (which constantly engage both the center shaft and the outer ring) is connected directly to the ICE. The outer ring is hard linked to the large motor-generator (MG2), and is geared directly (via the final drive, of course) to the drive wheels. The whole thing is so compact that it requires only four quarts of ATF (versus about ten more in the multi-speed autos).

 

[ekpolk]

Originally Posted By: Bill in Utah
Reading the article I saw this...

Quote:
To maximize the chances that the standard Prius battery pack will survive 10 years under any conceivable operating conditions, Toyota rigorously keeps the pack’s state of charge—expressed as a percentage of the full-capacity charge—between 50 and 80 percent. Toyota does not disclose exact details, but some engineers say the band is even narrower under most operating circumstances.


So, when you are going down the freeway (my big problem when I've been in a Prius) and we come to a grade, the engine just has to scream up the grade, is it because the battery will not be allowed to help?

Or let me ask this, *if* they allowed the batteries to go lower could it help going up grades and such?

Just wondering.. Bill


It's 40-80 percent. When I still had the CAN-view unit installed (it's out for repairs), you could plainly see the SoC percentage. I've actually seen it dip as low as 38%, but never go above 80%.

The battery will help just fine -- until you hit about 40% SoC, then the ICE is pretty much on its own. Bill, you bring this up all the time as it it's a commonly seen problem with the car, but it's really confined only to long-distance, extreme, hill climbs. I occasionally drive my battery into the pink bars, but that's when I've been deliberately milking the battery. When you do, performance does go a bit flat. OTOH, I've never bled it dry on a hill climb, ever.

 

[ekpolk]

Originally Posted By: Bill in Utah
I love that this guy spent $25k for a Prius (got no problem with that) THEN spent another $32k

to save 12 cents a mile (normal Prius is 14cents, his 2 cents)

He will make his $32k back in only 266,666 miles. (if he did not invest it anywhere...)

Pass. Plus he is banking that his electric rate stays the same for those 266k (yeah right)

Or if the batteries last that long....

I don't get it.

Don't mess with a good thing. Let Toyota figure it out. (It will cost less than $25k +$32K in the end)

Bill

At last, we're in absolute, full agreement on something regarding the Prius. Mine's plenty economical, in bone stock configuration (well, I do play with cooling masking, but that's hardly like the mods that go to the genetic level). But most critically, I need mine to get me to work every day, and thus, I'm unwilling to do anything that might compromise that legendary Toyota reliability.

 

[glennc]

Originally Posted By: ekpolk
Originally Posted By: Bill in Utah
So, when you are going down the freeway (my big problem when I've been in a Prius) and we come to a grade, the engine just has to scream up the grade

OTOH, I've never bled it dry on a hill climb, ever.

Sounds like the difference between somebody who lives in the Rockies and somebody who lives in Florida.

Honestly I think we expect too much from cars as far as hill climbing goes. If it'll go up a good grade at sixty or so, even if the engine is working hard, what's the problem? That's the way cars used to be, and they worked just fine. Now we demand effortless high speed uphill cruising, but is it worth the cost?

 

[Bill in Utah]

According to the article, you can not get the battery low. Toyota keeps the battery within certain charges to protect it.

Glenn, the problem is when you have to go up a hill 2 things happen, 1st the car will not go up the hill at 60. Try around 50 with the engine really working hard. With the engine working hard, it drags down the MPG quite a bit in the 3 times I've been in one going up and down the state.

For higher elevations, the 1.5l is a little small. I think even if you put the 1.5 in the Corolla it would be too small. And the Corolla is lighter. 76 hp at sea level in a 2900+ lb car is ok when you have the batteries, at 7000-8000 ft (or more) going up a grade without it is tough.

The Corolla weighs 400lb less and has 50+ more HP. In this *one* driving condition it does matter (for me)

I know Ekpolk is about ready to nail me here... I better keep quiet!

I keep asking questions as I am just wondering how/why....

Bill

 

[Bill in Utah]

Quote:
At last, we're in absolute, full agreement on something regarding the Prius.

Take care, Bill

 

[ekpolk]

Originally Posted By: glennc
...Sounds like the difference between somebody who lives in the Rockies and somebody who lives in Florida.


Hey now, we've got some elevation here, especially in my part of the state (Panhandle). There's one place where it gets over 300' MSL! I get a nosebleed just thinking about it.

Seriously, though, I've had the car on trips in the eastern mountains a couple times, and not seen this problem there either. I wonder if air density at higher elevations may be a factor?


===============================================
Originally Posted By: Bill in Utah
According to the article, you can not get the battery low. Toyota keeps the battery within certain charges to protect it. ...


Again, that's correct; the lowest I've ever seen was 38%. That occurred last summer on a hot night while waiting in the Backyard Burger drive-thru, with the AC running. Why the ICE didn't kick in right at 40, which it usually does, is anyone's guess. Yes, the ECU stands guard, quite carefully, over the battery.

 

[Black Bart]

Everyone has different needs and what they want from a car but the more I read about the Prius the more convinced I am that I would not buy one.

Where I live and the type driving that I do it would be running on the ICE nearly ALL the time so I can buy something that cost less and gets the same hi-way MPG.

I'm looking forward to some nice turbo diesel small vehicle that will get 60 mph.
As far as making energy from braking their again it depends on where you live and your style of driving but I have few stops and I know way ahead of time where the stops is so I can coast to the stop sign without using hardly any braking.
I just sold a 6 cylinder Mustang with manual transmission that had 141,000 miles on it with the original brakes those who live in a large city would find that hard to believe but the difference in driving style is huge.

It is obvious that polk is very passionate about his Prius and I'm glad that is is working out for him but for my driving needs it just is not what I need all of my driving is open road driving the money saved buying a non hybrid will buy a good bit of fuel.
I have been driving for 60 years and never replaced a starter yet.
As to the engine being shut off at stops well when you don't have red lights to sit at their is no need to shut the engine off until I get to my destination.
The one town that I go to that has red lights I drive to make them without stopping and I'm always amazed at the idiots that drive as fast as they can just to stop at the next light this shows that most people don't even know how to get fuel mileage.

 

[ekpolk]

BB:

Don't worry, I don't sell them, and I would never want someone to buy a car that's not their cup of tea.

One specific response, to the braking comment. I think perhaps you underestimate the power of regerative braking. In fact, it's not just active braking. Any time you lift off the gas, the motor-generators immediately reverse into generator mode, and start feeding the traction battery. Get on the "brake" pedal, and the charge amperage goes way up. The only time that braking action is actually generated by the old fashioned friction brakes is when the car decelerates below about seven mph, or if the computer determines that you're calling for an emergency/panic stop. Otherwise, all braking is actually the conversion of motion into electricity, which you can use again later.

You're a lucky guy re starters...

 

[bob_ninja]

Originally Posted By: ekpolk
There are several kits out there, and sets of plans for conversions. And if you're up to it, you can make your own supplemental traction battery for a lot less than $10k. There's one guy who as a really nice looking one that he encased in a large Tupperware-type bin which fits into the compartment above the spare and below the main cargo floor (which is easily removable).

All this begs the question of why? Sure, for dedicated short-trippers, the plug-in feature can be a big plus (but you pay for that electricity too, so it's not a freebie).

Bob, I realize that "tiny" is a subjective term that can be interpreted in different ways, but I wouldn't call the traction battery that. Physically, it's about the size of a small-medium suitcase, and given the constraints imposed by ECU programming, you can get several miles of electric only running, if you drive carefully (or install an EV button). The ECU is programmed not to allow the TB's SoC to rise above 80% or drop below 40% of absoute capacity. This, and additional constraints on rate of charge, temperature, etc., ensure a long battery life.


My "tiny" reference was in terms of energy storage. 1 or 2 kWh is "tiny" in terms of car's requirements. I didn't say that it is useless. However, I think that a bigger pack, at least 5 kWh *USABLE* energy would allow for far more electric energy storage/recapture, etc. In other words, ICE would be able to remain idle for longer periods.

I realize that you are happy with 60ish mpg. However, I and many other people are looking for far more, at least 100 mpg. There is a big waiting list for GM Volt. A number of people express interest in zero gas use.

In some cases like this article example, people will pay a bunch of money for an expensive big pack despite poor economi return just to be able to use mostly electric energy and almost no fuel.

At this point due to Iraq, escalating costs of fuel and food, etc. it is becoming more than an economic issue.

Anyway, 1-2 kWh is fine as a very short term energy buffer. However, such a buffer has a limited usefulness.

 

[bob_ninja]

To clear up batteries ...

No, there is no 5 year lifespan limit on batteries. If they are abused then can die in 3 months. Some people have 2 year old NiCds still working.

There is a huge lifespan difference based on battery treatment:
- operating/charging temps
- SOC
- current draws

For instance, the old batteries would die very quickly for higher current draws, or in some cases cause fires and explosions. NiMH AAs are always charged to 100%, down to 0%, so they would last as little as 100 cycles. And so on.

These battery packs are managed to obtain the optimum balance. In particular, shallow discharge (40% SOC) and incomplete charge (80% SOC) *DOES* allow for many more cycles. If you consider older NiMH cells are capable of 500-1000 cycles, then these managed cells can easily go beyond 1000 cycles.

What is more, the new Lithium chemistries like Lithium phosphate are far superior to the ones used in laptops. I followed an experiment from RC dude that was *ABUSING* new A123 cells. After 1000 cycles they dropped to 80% of the original capacity, but still worked fine.

The bottom line is that the new chemistries are far more robust and capable of handling far more cycles. So they will be durable.

Note that this addon packs for Prius are *NOT* using Toyota's old NiMH cells!!!! They are using the new Lithium chemistry cells. So they will last plenty.

 

[bob_ninja]

Toyota has made the perfect design choice at the time when Prius was created. The tiny 2 kWh pack is cheap, yet provides the sufficient storage for short term energy recapture, as ekpolk explained many times. Thus Prius has established the new hybrid category.

This market segment will play a major role as GM tries to catchup. In fact, most larger SUVs, crossovers and other bigger cars will use this type of hybrid design as a standard equipment in the future. It is a no brainer.

That being said, due to escalating fuel costs (with no end in sight) there will also be a huge need for pure electric transport. We are talking about simple short trips, like for groceries, to work, etc. The electric power from grid is and will remain *MUCH* cheaper for a long time. Therefore, a lot of people will want a simple vehicle for simple short trips than involve no gasoline.

For these applications newer more expensive batteries will be necessary despite the cost.

Everyone looks at this from economic perspective alone. However, in not too distant future we'll start having shortages, supply disruptions, etc. When your local fuel stations run out of fuel then even Prius will be stuck.

Therefore, while it may *SEEM* crazy to spend so much money on battery pack and solar panels, he has achieved one important objective - self reliance. All the fuel stations can run out of fuel and even the grid may fail. Yet, he will be able to charge his car from solar panels, run his home from solar panels, all without any infrastructure.

I don't want to sound too doomsdayish, but this is something we ought to start thinking about. I don't care if my cars are all electric. However, I would like at least one car or even a bike to be all electric with a decent range.