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

page 10 of the PDF usbseawolf posted:

"For example, in cells discharged to 95% DoD per cycle, our measurements predict that 5300 cycles will be needed before reaching 80% of initial capacity instead of around 1500 cycles as indicated by the VARTA data. Also, daily cycles with shallower DoD values do not appear to increase cycle life as significantly as those indicated from the VARTA analyses. This suggests that a greater portion of the cell capacity could be used during each cycle than would be suggested by the VARTA plot if applied to this chemistry."​

this proves the point I stated, in this case they where testing LiIo cells from A123 systems, and they showed they could be discharged to %95 without greatly affecting their longevity, or their ability to hold charge.

Thank you for proving my point 5300 cycles at 1 cycle per day, could be 5300/365 or 14.5 years, before the pack only has %80 of it's initial capacity left. those are also full charge/discharge cycles, with will probably not occur with most EVs. As they say, shallower discharges don't really extend the cells life, either.

BTW, that study was done for determining vehicle use combined with V2G use as well.

Page 33:

 

A123 cells are really good with deep discharge. I have an electric drill with those cells and it is still going strong. The voltage is low for LiFe resulting in low energy density. It is not ideal for EV or PHV.

We'll have to see how other Lithium variations perform with deep discharge. I am especially interested in NMC cathode since Nissan and Toyota are working on it for their next-gen pack.

 

I am wondering about max power draw from the battery; MG2 would also have ICE input as needed, if I remember the HSD correctly.

Hill: watts are a power unit; power*time = energy.

 

Danny, what is the maximum speed the PHV can EV up to and not require ICE spin ? I don't mean fuel consumption, just ICE spin.

 

Your making the calculation too hard. If you take the energy needed to charge the pack, the used energy must be at most this number. The current phv prius uses at most 3.6 kwh. Divide this by the pack size 5.2kwh and multiply by 100% and you get the usable pack capacity. The other information can only help you decide what might be possible with a future pack with deeper discharge logic.

Yes the packs are being used in parallel. Toyota has stated that each of the 3 packs have the voltage of the combined pack which means parallel operation.

 

There is a flaw in that calculation. PHV Prius use only 2/3 of the pack for EV. 1/3 is for HV mode only.

I believe you are missing this information:

Source

 

I think it is neither parallel nor series. Each pack has 345.6v but they are disconnected (logically) from each other. Only one pack can connect to the bus at a time.

 

I believe he answered it in the original article.

 

The video linked to earlier in this thread tells a different tale -- I think.

Although capacity loss was only demonstrated down to 95% (who knows what happens after that), it was (1) linear, but interestingly (2), was dependent on total battery use unrelated to DoD pattern. The slope was 1000 Ah/1% capacity loss. If this pattern holds true down to say 70% of capacity, we can guesstimate the battery's useful mileage. I'll assume 240V, and 0.25 kwh/mile:

240 Volts * 1000 Ah * 4 miles/kwh * 30 = 29,000 miles.
If the system runs a 360 volts, about 44,000 miles can be expected.

WELL, not what I was expecting. If the numbers are right, they suggest a reason for the tri-pack arrangement: one throw-away battery for HV use (or a non Li-x chemistry), and two Li-X modules for EV driving. Lots of other conclusions suggest themselves, but I'll restrain myself until house gurus bless the arithmetic.

 

No, I'm not missing it, I'm just not using it. Let's make it a simpler story problem. You have three five gallon gas tanks on your car and they all read full. You use tank 1 and 2 until tank 2 reads empty, then you use tank 1 and 3 until tank 3 is empty. You keep driving until tank 1 is empty. When you refill all the tanks it takes 9 gallons of gas. What is the usable capacity of the gas tanks.

The answer is 9. All the other information can safely be ignored.
So in my story problem the car had a usable capacity of 60% of total capacity.

Toyota says they operate in tandem. This means that 1 and 2 are wired in parellel or 1 and 3 are in parellel, or 1 is used alone in pure hybrid mode.

Just for comparison the volt battery pack is 16kwh and weighs 375lbs. GM says they will charge up to 85% and discharge the pack down to 30%. These batteries are not the same as the small batteries for electronics.

Toyota's battery pack is much heavier per kwh. My guess on the three pack design is to see if the charge discharge cycles change usefull life. Packs 2 and 3 are only charged from the plug. Pack 1 is charged from the plug, ice, and brakes. If these multiple charge discharge cycles decrease capacity, it may only effect pack 1 so ev range will not decrease as fast. If your goal is at least 80% of the range in 10 years this may be a good way to do it.

 

That makes sense. I like to see the confirmation that the main pack also get recharged from the plug.

 

Good point, AG.
Certainly capacity loss is tolerated quite well in HV mode, so long as power flux continues to work well.

 

I want a tribrid: two li-x in parallel for high voltage, high power EV, and a super-cap for HV/regen modes.

Disclaimer: I know practically nothing about electricity, and definitely nothing about electronics.

 

Lithium Ion chemistries which include Lithium polymer have much higher energy densities than super-caps, which means Lion will be much lighter for a given range (they also have less volume than super-caps and Nimh). Super-caps have high power density and don't deteriorate on charge recharge cycles like batteries. So a super cap could be used to grab more of the power of regen braking, or a quick charge. It could also be used for the burst of power for acceleration. Super-caps also lose energy faster, so you can't just let the car sit and expect the energy to be there as it would with Lion batteries.

So in your scenario, super-cap for high power acceleration, regen braking and quick charging. Along with Lion for good energy to weight and energy to volume ratio.

 

and see here whe have the next gen 3 plugin prius
come on toyota.. make it.

 

While the Prius PHEV sounds great, we are talking a six or seven thousand dollar premium over a standard Prius. What, really, is the incentive for a current 2010 owner to ditch a nearly new and paid off (or close to it) car in 2012-13 for the PHEV as opposed putting that money into a good conversion? It just doesn't have that WOW thing going for it, IMHO.

 

It has the WOW thing for gen2 owners.

 

That's simply NOT true. That value is a figure (a bad one) from your imagination.

 

Actually, the $30,000 range has been a price many have mentioned, and is seen in Toyota's own presentation during the pilot rollout. I imagine that would also include a few extra goodies over a package II or III, and is really not an unreasonable premium to expect.

 

Would you be so kind as to give a link to download that presentation?
Thank you.