3 Words to Describe the Prius PHV Test Drive: "I Want One"

Some speculation.

I -suspect- the battery is split into three for a few reasons:
1. It makes the packs light enough to be legally lifted out by one person.
2. It's dangerous (for the battery pack) to parallel charge/discharge as it requires very sophisticated circuitry to control the charge levels in the two/three packs. So operating each separately is easier.
3. The lithium ion cells aren't available in large capacity at reasonable prices and good reliability, so smaller capacity cells were used.
4. It may actually be -possible- to regen. charge the depleted packs, but it would require a rather sophisticated charge controller. Perhaps they are developing that for the production car.
5. Some "real world" test data is probably needed for the above, not data engineers gather then -they- drive the car. So it may have been left for the production car's introduction.

-I- would like a larger capacity battery pack in Pearl, but it would only be useful in the mountains, where I frequently topped out the stock pack near the start of the descent from a pass. So it's probably not an economically efficient idea.

The lithium ion packs I've seen (not the ones in the PHV, rather ones in the electronic industry) are about 1/3 the weight of NiMH packs. So I am guessing it's -possible- the PHV might not carry that much increased battery weight.

NiMH packs, when properly designed and managed (such as in the Prius) are almost bullet proof. In my experience (30 years in two way radio), as currently sold, they are about the most reliable batteries ever. As with anything, there WILL be failures, but they are rare. We just don't know what will happen with each different lithium technology/chemistry in the "real world". That's what this program (the leased "test" PHV Prius program) is all about.

Great story Danny. Thanks to you and Toyota for making it happen.

 

Building on David's comment, having the energy pack in three segments also means when one fails first, the repair cost is reduced. Also, a modular pack system supports a wider range of vehicles:

• singular - a people mover (the comfy chair)
• dual - compact
• triple - Prius sized
• more - use your imagination

Having recently replaced an NHW11 traction battery, a pack of half the size would have been a blessing.

Bob Wilson

 

It's useful where I live now which is hilly, not mountainous. I frequently hit SOC of 77%+ going down a hill to go home and have the car basically put itself into B mode (warmed up ICE fires up even and runs at high RPM even though I'm well below 42 mph).

I ride the "brake" most of the way down that hill so that I'm not well above the speed limit and also to keep below the 41/42 mph threshold.

 

I have been trying to digest the PHV pack information. I think I now understand why the pack is so heavy.

According to ESQ, Lithium PHV pack weights 330 lbs while the NiMH HV pack weights 110 lbs -- exactly three times. PHV pack has three subpacks each 110 lbs. We know only Pack1 and Pack2 are used in EV mode and they are charged back from the plug. The MainPack is only used in hybrid mode so I am going to assume it will not be recharged from the plug.

Previously released spec stated that the PHV pack capacity is 5.2 kWh with 3.56 kWh recharge power consumption. If Pack1 and Pack2 makes up 5.2 kWh then each must be rated at 2.6 kWh. This means each 110 lbs PHV subpack contains twice the energy of the NiMH equivalent (2.6 vs 1.3 kWh).

This reveals PHV Prius in hybrid mode will have twice the energy to absorb and propel it. It also mean all three packs combined has 7.8 kWh (2.6 x 3) of energy.

 

Maybe I'm becoming one of those stodgie ol' geezers yelling:

"... HEY ... get of my grass! ..."

... but all this hub bub about a PHEV from the factory ... with nothing for us common'ers for quite some time ... man, it's really starting to depress me ... kinda chave's my hide. (sigh)
ok ... taking a deep breath. re-composed. sorry.

:frown:

.

 

I think your math is off a bit. A common number is 250wH (watt hours) per mile, so most rate the EV range as 4 miles per KWh. If the total battery capacity of ALL three packs is 5.2KWh, divide that by 3, and you get 1.73KWH per pack, assuming only 2 are used for EV mode, that equals 3.46KWh, multiply by the commonly accepted # of 4 miles/KWh, and you get 13.86 miles of EV range, or remarkably close to the published number of 13.5 miles of EV range.

The "3.56KWh recharge power consumed" is because there are losses in charging, it is not %100 efficient, so it takes more than 3.46KW to put in 3.46KW, my guess is it takes 3.56KWh and that is probably with the pack only discharged to %85 or %90, they probably won't let it go below that for longevity.

Using 5.2KW for the 2 packs, you would get 20.8 miles of EV range.

An example is the Nissan Leaf, it is comming with a 24KWH pack, range is about 100 miles, very close to 4 miles per KWH.

 

The numbers you are using would require 0 to 100% SOC swing, which is unlikely.

What if you use 200 wh per mile. I'll need to run the numbers again tomorrow.

 

200 whpm is way too conservative. That would be what you could expect under perfect circumstances going very slow (like, <10 MPH). Their numbers reflect a more wide range of speeds I'm sure.

No, I agree--250 whpm is more likely what you will see in real life assuming you drive faster than 30 mph on average and/or accelerate fast enough to keep up with traffic.

I would expect a 70% DOD at most since Toyota is playing this whole Lithium thing very carefully and trying to cover themselves liability wise. I wouldn't be surprised if they limited it to something like 60% DOD. The real question is does Toyota do any sort of balancing to keep the batteries in sync on the curves at the high and low ends.

Andrew

 

You mean you want to put all those oil companies and gas stations out of business?
Heck, in America, that's like taking insurance companies out of health care.
Won't happen.

 

Lithiom-Ion has different discharge capabilities than Lead Acid, or NiMh, I think most are allowing for an %85-90 discharge, without damage to the batteries, or affecting their longevity. That has to be factored into the 13.5 mile EV range, so if we do some math, 13.5 miles / 4 = 3.375 KWh of usable energy required, then multiply that times 1.15 or 1.10 (for %85 or %90 discharge), you get a 3.88KWh pack required for %85 discharge, or a 3.7125 KWh pack required if %90 discharge is allowed

Toyota is saying it will take 3.56KWh to recharge to pack, and we have a pretty good idea they will need 3.375KWh of energy for the 13.5 mile range. You can work backwards from that number as well, but you would need to know the charging loss's, then you could calculate the size of the pack they are using, also it would help to know what the SOC maximum discharge # they are allowing as well. I think the %85 or %90 numbers are pretty close for LiIo

 

The battery pack is 5.2 kwh, in the current phv. What are you calculating.

You stated the answer, then you divided by two then multiplied by three. Showing your work only makes the bad math more obvious.

The current gen 3 prius uses approximately 40% of its battery pack. It charges to around 80% and allows discharge to 40%. Toyota is experimenting with their 600 phv prototypes to see what the charge discharge will be. Currently its usable charge is less than 70%. YMMV, and toyota may very well change these numbers and even the energy stored in the pack by the time of commercial release .in 2012

 

Yes, and the current Gen 3 Prius uses NiMh (Nickel Metal Hydride), a totaly different battery chemistry than LiIo (Lithium Ion), so that number means nothing. LiIo has a higher energy density, lower weight, and a deeper discharge curve as well. Most EV mfrs are going to use more than %70 of the packs capacity, if not you need larger batteries, which cost more, and weigh more, and it may not be cost effective. Where does it say the "usable charge is less than %70", I have not seen that.

 

Yea, 250 whpm is more realistic since you can do 70 mph. 200 whpm is not as bad as you stated as it can do 50+ mph.

Source: Prius Palm Mileage Simulator

 

I did work backward and it did not make much sense.

If the three packs combined is rated at 5.2 kWh, then pack 1+2 would have 3.467 kWh. 13.5 miles would consume 3.375 kWh so you are left with 0.081 kWh. That's a very deep discharge... 98.5% SOC swing.

It makes me wonder if they are using some of the SOC from the Main Pack.

 

On the same page as you, usbseawolf.

Are we *sure* the packs are not being accessed in parallel ? Danny's experience of staying in EV while getting on a freeway is a good 50 kw power draw, no ?

 

I am trying to find out if 5.2 kWh is the energy in the entire PHV pack or just the subpack 1 and 2.

If we assume 5.2 kWh is the energy in all three subpacks, the Lithium offers very little energy gain over NiMh. 110 lbs NiMH HV pack has 1.31 kWh. 110 lbs Lithium PHV subpack has 1.73 kWh. This gives Lithium 32% more energy per pound, way short of 200% expected.

That lead me to think if the 5.2 kWh is for just the subpack 1 and 2.

 

If you take the expected DoD improvement into account, the useable energy density looks like promised:

NiMH: 1.3*.4 = 0.5
Li-x: 1.7*.8 = 1.36

1.36/0.5 = 2.7

 

50kw is not a rating. There has to be a time frame ... seconds minutes or hours. Since getting on the freeway is a paltry 7 or 8 seconds ... that translates out to maybe a ballpark of .250kwh if my napkin math is up to par.

 

You can not hypercycle Lithium to extend it's life like in NiMH.

This has been confirmed by the recent research Toyota presented. See 1:30 in the video.

Attached PDF is the study referenced in the video.

 

MG2 can draw up to 60kW during acceleration but less at other times. There will be time when it will return energy back from regen braking as well.

On average, PHV Prius should consume about 250 watt hours to travel a mile. That is the same amount of energy as two 125 watt bulbs for an hour. PHV Prius would consume the same amount of energy in one minute if it is moving at 60 mph.