Toyota Cuts PCU Cost by 30% for New Prius

They have also reduced dramatically the amount (and length) of high voltage cabling by the new arrangement (on top of the transmission).

 

nice. let's hope there isn't a failure/recall like gen III.

 

I noticed that GM and Toyota made very similar improvements in this area in their new generations. Both of them:

1. Integrated the power electronics onto the top of the transaxle to eliminate high voltage cables

2. Increased density by mounting the power electronics circuits on both sides of the circuit boards

Overall, the volume of the GM unit was reduced from 13.1 to 10.4L and the weight from 14.6 to 8.3 kg. Inverter switching losses were reportedly reduced by more than 50%.

I'm hoping Toyota will have a set of new SAE papers for next April's World Congress covering the engineering changes for the 4th generation Prius.

Here is GM's SAE 2016 Volt inverter paper from earlier this year:

http://www.delphi.com/docs/default-source/2015-sae-technical-papers/power-dense-and-robust-traction-power-inverter-for-the-second-generation-chevrolet-volt-extended-range-ev.pdf?sfvrsn=2

 

And you probably meant to mention moving the traction battery forward reduced their cable length and mass. Also, having the 12V battery in the engine compartment reduces that one too since the major 12V loads (i.e., brake controller) are in the engine bay.

The only thing I don't care for is the new 12V battery that appears to be significantly larger than the earlier Prius. I would rather have a smaller 12V with a solar array to handle parasitic loads. Better still, an 11-cell, 12V NiMH battery. Oh, I could do this. <GRINS>

Wait one! With a DC-DC converter for the 12V system, why is such a large 12V battery needed? It strikes me that power-up should start the DC-DC converter before doing power up of the brake actuator.

Bob Wilson

 

I expect that one of these generations they will eliminate the separate 12V battery, and power the 12V devices from the HV battery via the 12V (or is that 13.8V?) converter.

 

Actually, I meant the high voltage (orange) cables...but yes.

Doesn't this mean the HV battery should stay connected at shutdown? Brrr...

 

The current setup powers the computers through a test routine BEFORE the HV battery is allowed to power any part of the car outside the battery case. I doubt any lawyer anywhere will allow that to change. 201v (or even 144v for you c owners) is way more dangerous than 12v.

(for us v owners, the '12v' converter seems to make 14.4v, I got 13.8v on my Gen 2)

 

They should just add another Ni-mh battery like the one you find on Power Tools, cheap, small and effective.

 

I think the larger capacity (and probably more common) 12 V battery is a blessing improvement. See all the threads on battery issues, length of non-use time etc.

 

This is where solar cells can handle the parasitic load. Toyota already has experience with car-top solar arrays.

One reasonable approach would be to put the 12V DC-to-DC converter inside the traction battery case. There would be a challenge dumping the heat under load, 2kW * (100-92)% ~= 125 W but this isn't the only approach. The traction battery could provide a 12V tickle charge, ~30 ma. using the existing 12V power line to the battery controller. Keeping the 12V at optimum charge level means a lighter 12V battery with longer life.

BTW, I'm OK with considering liquid cooling of the battery pack. For the cost of two pipes and wire-ORed the inverter coolant pump, it would keep the traction battery in a 'happy place.' Alternatively, let battery temperature management operate after shutdown (NiMH charging is exothermic.)

GOOD GRIEF! Are we starting the Prius 2021 improvement list before the first 2016 is sold? No, we're just looking at the long history of Prius, 2001-future, to identify what appears to be low-hanging fruit.

Bob Wilson

 

toyota must have extensively tested liquid cooling, versus whatever they came up with to make these batteries last so long.

 

Maybe the 12 volt battery in engine bay is now a conventional flooded battery? Between that and the (apparent) regular size posts, should bring replacement cost down.

 

agreed, should be able to shove just about anything in there, but probably won't have to for 8-10 years on average. should handle the dome light issue and etcetera.

 

Putting the 12V converter inside the HV battery box would allow the high voltage connections to still be turned off.

For the case of lights left on, the 12V output would need some logic to turn it off before the HV battery was completely drained. Then press a reset button to turn the 12V back on, or maybe detect that an external 12V charger has been attached. It's a problem, but there are solutions.

 

I've seen up to 15v on cars. It varies depending on load.

NiMH self discharges faster than lead-acid. It could lose lose up to 30% of its charge over a month.

 

Depends on the cells, I have some Sanyo Eneloop that after months in a drawer work just fine.

 

So 7 dual power cards equals 2 three phase bridges for the MGs and one card for the DC/DC converter. I wonder where the air conditioner's bridge is?