Is a Prius inverter good for an EV?
 

I have converted several vehicles to electric DC systems. I recently bought this power inverter from a salvaged Prius. I have some wiring info on it but not much. Do any of you Prius experts know if this would be good for an EV controller? If anyone has any wiring info of any other input, I would love to hear it.

Brian

http://www.nwaev.com/prius1.jpg
http://www.nwaev.com/prius2.jpg

Several of us have spare inverters but the electrical interfaces to the inverter are not well documented. Good Prius friend Hobbit has looked closely at an NHW20 inverter. I've been a little slow but it is on my 'to do' list.

I've always figured I'd have to 'scope out' the likely signals but that remains on my "to do" list.

The Prius MG1 and MG2 are AC motors in a "Y" electrical configuration, three-phase. I don't know what typical EVs use for motors.

Encoder signals from the motors flows to the hybrid vehicle ECU that drives the circuits. It uses a high frequency, 90 degree offset, stimulus/sensor coils around an excentric disk. But again, the exact signals are poorly understood.

Bob Wilson

The Prius inverter is a fairly undocumented part with some impressive power electronics and internal control circuits. But Toyota has not been very 'open' about the exact specifications. The maintenance manual and SAE papers give some clues but it was really designed to work with the associated MG1 and MG2 in the transaxle.

What you have is an NHW11 inverter, 2001-03. Some of coarse specifications are available via Wiki:

• MG2 - 33 kW, 44 hp
• ~275 VDC traction battery - 20 kW maximum draw
• MG1 - 14.5 kW, 19 hp (from memory!!!)

Now the interesting thing is a significant amount of power flows between MG1 and MG2 all the time. What I don't know (no one knows) is if you could drive MG1 and MG2 from a combined 33+14 ~ 48 kW, ~64 hp. But the battery leads were designed for something under 20 kW. Worse, to make it work, you'd need three traction battery packs and balancing multiple packs is not a trivial problem. So then you start looking at building this 275 VDC, +48 kW battery pack and that too is not trivial.

My interest is in something a little more modest ... house co-generation. It should easily handle generating up to 14 kW of pure sine wave from a running, parked Prius. This would be a very, very nice thing to have.

Bob Wilson

You have got to be kidding. That is like the absolute worst thing you can do with gasoline.

As a backup for when the power is down, a PriUPS would be very handy. As a method of displacing grid electricity, it's very wasteful and expensive.

Relax folks, my co-generation plan is a little more involved than just the inverter. I already have Prius emergency power. Our family uses it for about 8-24 hours about 1-2 times per year. We've used it twice, already this year.

Bob Wilson

Hi,

A fellow out in western Mass powered his house (or part of it) with his Prius for 3 days after an ice storm knocked out the grid -- and he burned just 5 gallons of gas. That was a nasty ice storm and the power company was sleeping on the job -- some other folks were without power for about 2 weeks...

Just having it for a DC to AC 3 phase converter alone is worth what I paid, but I am interested in finding the wiring diagram for the harnesses. I know which is the DC input and the 2 AC motor outs, but I was looking for a way to find the throttle and sensor inputs. I may have to buy a complete harness and computer to get that info and when I do I will post the results. Thanks for the replys.

Brian

If used with wind and solar power to charge the batteries, I think it would be a great way to displace grid power. Just a thought and thanks for the quick reply!

I would recommend:

• Toyota Prius Electrical Wiring Diagram - EWD493U (pp. 58,59)
• A working NHW11 Prius and storage scope to work out the interfaces

But you are reaching the boundary of what is known.

Bob Wilson

I did some research about the Prius inverter for my ECEN 370 class, and here's one of the best links about the inner workings:
Prius inverter
In summary, if it's possible to obtain one for cheap enough and figure out how to use it with your own controller, it's good for a homemade EV. In addition to the inverter itself, you also get a boost converter, accessory 12v PSU, and an accessory (A/C) inverter. It is especially good for the beginner EV builder since the details in the power electronics are already done. (But I, as an electrical engineer, would prefer to build from scratch unless it would be much cheaper to just use a Prius inverter.)

The nominal input voltage is around 200v, which is about 16 common 12v batteries. The Prius motors are 500v, which is close to the 480v of common industrial motors. The main problem is that it gives you two outputs when you really want one. It's not possible to parallel them as you cannot guarantee synchronization of the drive signals. Perhaps you can use two motors, one about twice as large as the other, couple the shafts together, and parallel the drive signals.

But what off the shelf controller will know what to do with the power factor corrector? This sounds like a custom controller to reuse the power components in the prius inverter, which is good for maybe 60hp and severely limits your motor options.

Caps and surplus IGBTs and handwound inductors can be had for much less than a typical used prius inverter and are in greater supply.

For beginners, it could be useful since there is much less to build. It obviously won't be as useful for the electrical engineers.
I think the boost stage controller is integrated into the inverter. If that's the case, it's just a matter of connecting the control connections to the microcontroller. If not, there are plenty of off the shelf PWM chips that can do it.

It sounds like you have to be an EE in either event :) Might as well put your efforts into something that isn't proprietary, assuming you are not on the toyota payroll.

What are the inputs, what about battery selection for regen, how about the motor(s)? when it decides not to run for lack of an engine then what? What if the voltage cutoffs are not appropriate an ev?

I've considered repurposing controllers before, I couldn't make it make sense, was easier to start over with a thorough understanding of what you wanted it to do.