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Prius battery power conversion

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moodymike

Thu Apr 22 2010, 05:40PM

Registered Member #2800 Joined: Mon Apr 12 2010, 03:09PM
Location:
Posts: 8

What are the possibilities of using a prius as a "generator" to run electrical (110v) in case of a power outage. At the battery lugs it is 500v DC. The car will automatically start and charge the batteries when voltage gets low, so what would be the best way to go from 500v DC to 110v AC?

klugesmith

Thu Apr 22 2010, 06:51PM

Registered Member #2099 Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1716

moodymike wrote ...
At the battery lugs it is 500v DC.

The Internet says the nominal voltage is 201.6 volts starting with Gen3 (2004 models), and early model Prii used no more than 288 volts.

I think a high capacity UPS unit (that normally uses a separate rack- or floor-mounted battery pack)
would be a good design starting point. A problem with transformerless H-bridge inverter is our desire for AC output with one wire at same potential as vehicle chassis and a HV battery terminal.

Deep cycling is hard on the hybrid propulsion battery, just as it is on a regular 12V car battery.

[edit] If we compare the Prius propulsion battery pack with 202 volts worth of alkaline D-cells,
the D-cells have about twice the energy (2400 Wh) and about half the weight (19 kg).

moodymike

Thu Apr 22 2010, 07:49PM

Registered Member #2800 Joined: Mon Apr 12 2010, 03:09PM
Location:
Posts: 8

You are correct, everything I read on the internet points to 201 volts, but somewhere in the manual it states 500 volts..... or maybe I am just getting old, I cant remember correctly :(
A good 12v inverter at say 3000 watts are easy to find, and not too expensive. So to go that route, it would just be a matter of droping from 201v to 12v, or would it be better to design one that runs on a higher voltage.
I really only am considering this for emergency use.. so its not like the batteries would get beat up too much..

Jrz126

Thu Apr 22 2010, 08:33PM

Registered Member #242 Joined: Thu Feb 23 2006, 11:37PM
Location: Erie PA
Posts: 210

The prius already has a huge inverter to drive the electric motors. It'd be interesting if you could hack the control electronics into putting out a constant 60Hz 120V.

Dalus

Thu Apr 22 2010, 08:46PM

Registered Member #639 Joined: Wed Apr 11 2007, 09:09PM
Location: The Netherlands, Herkenbosch
Posts: 512

yes we can do it better then the solution in the link. Though this is nice and easy

Steve Conner

Fri Apr 23 2010, 09:27AM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

I don't know about the Prius, but the Tesla Roadster already uses its traction inverter as a PFC front end for charging the batteries, and uses the motor windings as the filter inductor. It would be pretty trivial to throw it into reverse and use it as a UPS.

This technology was patented by Alan Cocconi of AC Propulsion, so you won't see it on other EVs that don't use his drives. He calls it "reductive charging", and he had the EV-as-a-UPS concept in mind when he developed it.

He even says that it's bidirectional here.

The main problem with the Prius is that it has a very small battery. You'd have to run the gas engine to use it as a worthwhile power source, and that would mean major firmware hacking. I wonder when the first open-source replacement firmware for the Prius will come out?

As for the 500 volt figure: The Prius's traction battery is around 200 volts to be sure, but it uses a boost converter between the battery and the traction inverter DC bus, which runs at 500 volts.

In fact, it has two inverters and two motor-generator units, coupled to the transmission in a complicated way. I don't know if it is possible to use one of the MGs as a generator with the car stationary, the wheels might need to be turning.

an explanation of the Prius transmission

klugesmith

Sat Apr 24 2010, 06:28PM

Registered Member #2099 Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1716

Steve McConner wrote ...
...In fact, it has two inverters and two motor-generator units, coupled to the transmission in a complicated way. I don't know if it is possible to use one of the MGs as a generator with the car stationary, the wheels might need to be turning.

an explanation of the Prius transmission

Thanks for the link, which has the best explanation I've seen.
To complement that, here is one of several interactive simulators.

Too bad it does not show the kW state of the ICE and MG's -- that would need another knob or simulation layer for the torque at wheels.

I think AC Propulsion's biggest factory order (as opposed to licensed technology) was 500 complete drives to BMW for the Electric Mini project.

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