Can the smaller Prius C battery power household appliances?

Has anyone done this yet with a Prius C ? I thinking of doing it with 1000w sine inverter and hooking it up to the 12 v battery. Is That too much? I found a great price on 1000 w inverters, but was thinking a 700 w would be more appropriate.

 

The real issue is the capacity of the 12V charging circuit. My guess would be about 1kw - any more and you're going to run down the 12V battery. What you're really doing is running the ICE, which runs MG1 (2?), which delivers power to the HV battery. Then power from the HV battery is sent through some more power conversion to produce about 14V. The 12V battery is just there to start up the computers and operate the lights before the car is made READY. People regularly kill the 12V battery by just listening to the radio for an hour with the ignition in ACC. Not much power there.

 

RobH Theres stories of people running 1k inverter off regular size Prius for days off the 12v battery. I was just wondering if it would be similar with the smaller Prius C. Or do I need to use a smaller inverter?

Do you know the most that could be pulled from the traction battery, safely? I'm not opposed to using traction battery, just seems a lot more involved and twice the money.

 

The limit is not the battery, it's the conversion electronics between the engine, the HV battery, and the conversion electronics to the 12V battery. The batteries are just temporary storage that cover for periods when the engine isn't producing enough power. Neither battery can survive being emptied, and even full they don't hold that much.

That said, my guess is that the 12V battery can source something near 1000 watts, and the HV battery several thousand. The real power is going to come from operating the gas engine. The C and the full size Prius both require about the same 12V battery capacity. They both use about the same number of computers and light bulbs which are supplied from the 12V source.

The only way I know to determine how much you can pull off the 12V system is to try it. Draw too much and you'll blow the 100 amp fuse (1200 watts). Draw more than the conversion electronics can provide and the 12V battery voltage will drop from the normal 14 volts or so down to below 10 volts where the computers will go wacky and eventually shut down. If the 12V inverter you use doesn't include it, I'd add a voltmeter to the system to watch for the voltage going too low.

 

Or your car will turn the engine on more often to charge the battery and your MPGs will suffer accordingly.

 

I very confused by the claim that you can draw 100A from the 12V system. The owners manual say don't draw more than 10A from the power outlet. Are you getting it from somewhere else? Are you modifying the car to get this?

 

100 amps directly from the battery, 10 amps through the standard power outlet.

 

The ten-amp power outlets are limited by their small fuses and wiring the size of angel hair.

If you attach directly near the battery, and you use wire of appropriate gauge, and fuse it accordingly, you can draw somewhere up close to the DC/DC converter's output capacity, less whatever power is being used by the rest of the car.

I don't attach at the battery. There is a cable from the battery to the front of the car, and that cable is essentially fused at both ends (one fuse is integral with the battery post clamp, at least on the full-size Prii that I've known; I assume the c is also like that). I generally bolt to the cable side of that battery-post fuse, so that what I'm adding already has a fuse each between it and the battery, and between it and the converter.

The converter in a full-size Prius has a capacity around 1200 W or a bit more, some of which is used by the car, of course. A lot of the time, if you're using the inverter, you won't be using a lot of other loads (headlights, heat blower, wipers, etc.) at the same time, so there's more for you. As other posters have pointed out, you should really not be thinking "I'm powering my inverter from the battery", but "I'm powering my inverter from the converter."

One thing easy to forget, at least in the full-size Prius, in colder markets, is there is an electric supplement to the cabin heater, that comes on for quicker heat when the engine's not warmed up yet. That guy pulls around 700 watts. (I don't know if that's in the c or the same wattage; check the New Car Features manual or the wiring diagram for the details.)

In the Prius models I've known, there is a signal output from the converter called IDH, and the converter will raise that signal if it starts feeling fully loaded. In the original wiring, that signal doesn't go anywhere but the heater, which will cut out the electric supplement if it sees the signal. You might be able to tap it and light an LED or something, if you wanted to know when you're near the limit. (In newer Prii, that 'signal' might be a CAN bus message; earlier, it was an actual wire.)

Bob Wilson did some experiments years ago (early model) showing there wasn't any sudden or catastrophic failure if you drew above the limit; the converter's output voltage would start to droop, and then droop some more, until you really weren't getting any more power out of it than you were before. If it starts to overheat it will eventually say "I'm not doing this any more" and shut off, with an appropriate code. You could then be at risk of draining the battery, as it won't be getting charged, but pretty much any inverter you're likely to buy these days will also have a minimum input voltage and shut itself off, probably around 10.5 or 11 volts.

The computers in the car could in principle get "wacky" if the voltage gets pulled so far down that it's near logic-circuit levels of 5 volts or so, downstream of their onboard regulators that require about a volt of headroom above that. In practice you're not likely to see any such thing, though if you hit as low as 8.5 or 9, some of the computers are programmed to, and will, log codes that tell you that happened.

 

Thanks for that useful information. I figured out enough from other posts that I was willing to try the test today. The 750W inverter came today so I clamped to the jump-start post in the fuse box. I had no trouble powering my 200W fridge. Everything (climate, radio, etc) was off, only dash lights on. Inverter never got warm. So it all worked great.

From what you and others have said I should be able to push it further, maybe up to the 750W limit. It would be nice to power the computer (~400W) in addition to the fridge. The engine runs about 20 seconds every 10 minutes with just the fridge so I imagine it would just run more frequently if I drew more power.