Poll: will it work? Prius as a generator, direct charging of 48V from traction battery

[AntronX]

So it's a 3rd gen Prius with 42kW MG1 up to 13500 rpm coupled to engine via 3.6 gear ratio, limiting you to 3750 engine RPM while stationary. @sunshine_eggo ?

 

[AntronX]

On another thought, maybe solar MPPT idea may not be healthy for that converter if constantly writing current limit values over CAN could wear out internal memory cells. I guess it would store those values every time you set them. After > 100k - 1M writes it could fail. That's only 2 - 18 months worth of use if CC is written every second for 12 hours/day.

 

[sunshine_eggo]

So it's a 3rd gen Prius with 42kW MG1 up to 13500 rpm coupled to engine via 3.6 gear ratio, limiting you to 3750 engine RPM while stationary. @sunshine_eggo ?

I'm less familiar with the Gen 3 specs, but it won't go above idle rpm without a foot on the gas. Still limited to about 4000-5000W unattended generator power, and it doesn't willingly engage the forced charging process I mentioned previously. It will do it briefly, but you have to cut the throttle and then re-floor it about every 5-10 seconds.

You'll want to pull the case cover and attach your feed wire at the main (+) and (-) terminals. The current sensor is integral to the relay, and

 

[McKravitts]

Thank you for telling me how to refer to a platform I've been servicing for 8 years. Unfortunately, you are wrong. The most appropriate reference would be to say "in READY mode."

I wasn't "telling you" you how to refer to anything. I don’t know the terminology that service professionals use, but it's clear that you understood what I was referring to.

Nope. We're comparing fixed rate 4kW power generation. Generator auto-start is a readily attainable feature, so duty cycle isn't relevant. A dedicated generator can be programmed to come on at X% SoC and shut off at Y% SoC. Or one can manually start/stop a traditional generator. I don't think anyone with an inverter and battery is going to run a 5kW generator when the load is only 100W.

In your original post, you didn't say that the "fixed rate" 4kwH generator was going to be charging batteries. Nor that it had to have programmable shut on/turn on and/or be manually started and stopped. All the things that a Prius does automatically.

The Prius doesn’t run a 5kwH generator to power a 100 watt load.
It runs the generator to charge the traction battery. The traction battery then supplies (via a dc to dc converter) 12 volt power to the car, which then can power an inverter which supplies the 100 watts.
Are you saying that when sitting idle in the "ready mode" the IC engine starts if one turns on the radio?

On the topic of fuel efficiency of gas powered engines, I have one question.

When powering a fixed 10 kwH load, what's more fuel efficient;
Two synconized genertaors optimized to run at 5kwH and each running at that output ?
Or one generator optimized to run at 10kwh and running at that output?

 

[sunshine_eggo]

Are you saying that when sitting idle in the "ready mode" the IC engine starts if one turns on the radio?

I've already answered this twice on the first page, and you even quoted the answer.

On the topic of fuel efficiency of gas powered engines, I have one question.

When powering a fixed 10 kwH load, what's more fuel efficient;
Two synconized genertaors optimized to run at 5kwH and each running at that output ?
Or one generator optimized to run at 10kwh and running at that output.

About the same.

 

[billvon]

Why not hook up one of the high voltage inverters directly to the drive battery system?

Because that AC to DC supply is isolated; your typical (non-transformer) inverter is not.

 

[McKravitts]

I don't think anyone with an inverter and battery is going to run a 5kW generator when the load is only 100W.

Unless they have a big battery bank to charge.

 

[Consumerbot3418]

constantly writing current limit values over CAN could wear out internal memory cells.

Based on behavior I’ve seen, the voltage and current limit isn’t stored in non volatile memory. If CAN comms is lost, or power cycled, it reverts to default voltage, which must be written to nonvolatile memory. At $50/unit, seems worth a gamble to experiment.

You'll want to pull the case cover and attach your feed wire at the main (+) and (-) terminals. The current sensor is integral to the relay, and

I’d sure like to know how this sentence ends!

So it's a 3rd gen Prius with 42kW MG1

I’ve seen close to 100 amps at over 200V while using regenerative braking… The behavior @sunshine_eggo described makes it sound like they’ve built in a duty cycle in software/firmware. Might be willing to push it if it was a salvage unit, airbags deployed, etc. But don’t want to risk exceeding specs on a vehicle used for commuting.

 

[sunshine_eggo]

Unless they have a big battery bank to charge.

Precisely my point. Generator charging is typically at a consistent power level, hence why I compared two generators running at 4kW thus negating duty cycle as a consideration.

 

[sunshine_eggo]

I’ve seen close to 100 amps at over 200V while using regenerative braking…

You're also charging with MG2, not MG1 when braking regeneratively. 90-100A is pretty typical if you hit the max regen braking conditions.

The behavior @sunshine_eggo described makes it sound like they’ve built in a duty cycle in software/firmware. Might be willing to push it if it was a salvage unit, airbags deployed, etc. But don’t want to risk exceeding specs on a vehicle used for commuting.

Just so I understand, what do you mean?

 

[McKravitts]

Precisely my point. Generator charging is typically at a consistent power level, hence why I compared two generators running at 4kW thus negating duty cycle as a consideration.

Can we conclude that using an inverter on a Prius for low power applications may not be quite as efficient as hauling a generator around but it's OK?

 

[sunshine_eggo]

Can we conclude that using an inverter on a Prius for low power applications may not be quite as efficient as hauling a generator around but it's OK?

My opinion on its use is very clear. My issue has been with the claims that it's going to be more efficient because... you know... Prius.

 

[Consumerbot3418]

Just so I understand, what do you mean?

I was referring to this statement:

It will do it briefly, but you have to cut the throttle and then re-floor it about every 5-10 seconds.

@AntronX seemed to float the idea of hacking the ECU via CAN to get a sustained 16kW output. But if the Toyota guys implemented a time limit on the forced charge like you described, then I don’t think I’d even want to attempt to seek that kind of continuous output. At least, not on an otherwise functional car.

 

[McKravitts]

My opinion on its use is very clear. My issue has been with the claims that it's going to be more efficient because... you know... Prius.

Agree. It's not going to be optiminally efficient, but how many generators are?

 

[AntronX]

I recall reading somewhere that 3rd gen Prius engine is 38% efficient at peak efficiency. Compare that to typically 19% efficient generator.

 

[sunshine_eggo]

I was referring to this statement:


@AntronX seemed to float the idea of hacking the ECU via CAN to get a sustained 16kW output. But if the Toyota guys implemented a time limit on the forced charge like you described, then I don’t think I’d even want to attempt to seek that kind of continuous output. At least, not on an otherwise functional car.

Best to consider the Prius as a 4-5kW generator. That's 96kWh/day or more...

 

[Mason Parsons]

The traction battery can handle up to 250V AC or DC, it might work to directly charge your 48V battery with the Eltek Flatpack2 HE rectifier modules. Just make sure to monitor everything closely, especially the voltage levels, to avoid any mishaps.