I;m moving to a new house. My thoughts are a portable generator would be nice to have on-hand. But, a generator could be a thing I never use.
That lead me to wonder, could an automotive inverter, clipped to the tiny 12v car battery of my Prius be strong enough to run my refidge? When I think of the things that could be most essential to run on a generator, my thoughts are:
refrigerator and sump pump. A few lamps might be nice too but those wont draw much. I do have a simple window AC, just enough to cool one bedroom...that could be nice.
Googling tells me a typical refrigerator is 300-800w but kick on surge could be as much as 3x higher or 2000w. My specific small AC unit is 850w.
So, if this is possible...is it wise?
Furthermore, if it is possible, any recommendation for a specific model?
My reasoning for Prius is that the gas engine shouldn't need to run all the time, just to recharge the battery, which it will self-do. It is a tiny 12v battery. Do you think the engine will need to run near-constant to feed the small battery?
Would this require an inverter so expensive that it might be cheaper to buy a portable generator?
I do not think this is a smart approach.
For one, the 12V battery would need to be constantly putting out around 60A to power an 800W fridge, not accounting for inrush current. Then you need to account for transformation losses (you'd be going from DC to AC) of 10-20%, too. When the engine did kick over (if you could get it to just automatically start when the 12v battery was low) you'd have to be running a heavy-duty alternator to provide enough current to recharge the battery.
I may be mistaken, but I don't believe that the Prius hybrid system is meant to charge the 12V battery. It's my understanding (which, again, could absolutely be wrong) that the 12V battery is for starting the engine and running accessory power and the hybrid battery is used for powertrain operation.
If you want a fridge that can run off 12V, look into 12V camping refrigerators. They'll still take an additional toll on your battery and alternator but at least they're designed for native 12VDC.
Or just get a small generator -- 3kW running output should do you if you're clever with managing on/off cycles -- and call it good.
I know someone who did this. You don't want a 12v inverter off the lead-acid battery, you want to run it off the NiMH hybrid battery. He did it with a second gen (in the US, 2003-2008) Prius. He scavenged the inverter by buying a used enterprise-grade UPS with dead batteries that was expecting the right voltage (I think it was 48 volts, but don't quote me on that), and then hooking the inverter directly to the NiMH battery. Left the car in "run" and it would monitor the battery state and auto-start/stop the gas motor to recharge it.
IIRC it worked for a year or two and then stopped. He was using a salvaged/crashed Prius, which was no longer weather-tight, and I think the rain got in it.
If not possible, look into the PriUPS: http://www.priups.com/riddle/answer-1.htm The concept is using the hybrid battery directly to power an inverter instead of the 12V. Good concept, but the rabbit hole goes pretty deep. I have a couple surplus UPS units that a hospital got rid of when the batteries aged out. Maybe some day I'll go deep enough to put one together.
Edit... Saw codrus's post just after I posted, same idea.
A single car battery would last about 4 seconds with a decent sized fridge
In reply to John Welsh :
I'll sell you my 7000w John Deere generator for $300. I don't need it since I installed a whole house unit.
I have seen it done, inverter hooked to the 12v battery. Priuschat is the place to go for info on this.
I did this with my Leaf. 1000w inverter, hooked to the 12V battery, plugged into the transfer switch on my panel. It ran my fridge and a light or two just fine.
You'll want a bigger inverter to be comfortable, and as others have alluded to your limiting factor will probably be how quickly your Prius can charge its 12V battery. A Leaf has a DC-DC converter that can charge at about 1500W, but I don't know how a Prius charges its battery. If it's just an alternator, then it will probably be running the engine a lot to keep up.
Probibly possible but not practical. You may be better off investing in solar panels and a battery bank with an inverter. Probably cheaper (depending on how you cobble it together) than messing with a Prius. Add a very small gas generator (think Honda/harbor freight 2000 watt unit) as a back up to the solar.
It would probably not be able to power the whole house all the time but as a backup system and careful management of power usage during outages it would probably got you buy.
Edit: just realized there is a lot of "probablys" in that post. 🙂
The Prius does NOT have an alternator on the engine.
It charges the 12V battery through a DC to DC step down from the High Voltage (~220V) Traction battery.
This is really an inverter/power vs. Cost $$ question.
In reply to John Welsh :
BTW, Congrats on the new house!
I hope it has a HUGE garage too.
If your Prius has a Group 25 battery, it has a reserve capacity of about 100 minutes. That means you can pull 25 amps off of it for 100 minutes before the battery reaches 10.75 volts. That's not a lot, and you don't want to drain a lead acid battery that far repeatedly, or you will destroy it.
The refrigerator and lights shouldn't be a problem. Lights are a low draw if you use LEDs and the refrigerator won't run much if you keep the door closed. There will be plenty of time to top the battery off while the refrigerator is in its off cycle.
Air conditioning is another story. That is pretty much a continuous draw down here, maybe less so in the northern states. Your window unit, at 850 watts will be drawing 85 amps off of your battery. Realistically, the battery can probably run that load for 25 minutes.
The other thing you may run into is the output capability of the charging circuit for your 12v battery. It may not charge at a high enough amperage to run the load and keep the battery full. A quick google search shows that it may top out at 70 amps. If that's the case, then the AC is out. Even with the engine running it won't replenish the battery faster than it is being drained.
So I've run my fridge off of a HF inverter run off my car battery. So, yes, it can be done.
The better question is IF it should be done, or is there a better way. Which is a very different rabbit hole.
So many things to unpack here....
Whats the use case? If you expect to be without power for just a couple hours I wouldnt even mess with a generator unless you have a sump pump or some other life-critical appliance you need to keep running. A fridge will be fine for a few hours as long as you are not in and out every 20 minutes.
If you just want to run a fridge once in a while for a few hours or even a day or two, one of those Bluetti/Jackery/Goal Zero in the 1000-1500 watt hours will run a fridge for a good long while and have enough inrush current. The nice part is fridges are intermittent duty, so you can run the fridge, then charge your battery pack for a few hours, then run it again and be just fine.
If you are already in the M18 or DeWalt universe, one of their battery banks with 120VAC output makes a ton of sense. I always have 6-8 M18 batteries charged up and ready to go. Then you are not stressing on a second battery running flat when you don't use it.
As far as running it off a car, sure you can do it, but as was already stated, the alternator isn't really made for it, neither is the battery. It will do it for a bit though if you ever get in hot water.
It will require an inverter so expensive that it would be cheaper to buy a portable generator.
You can't drive a generator, though.
Pete. (l33t FS) said:
It will require an inverter so expensive that it would be cheaper to buy a portable generator.
You can't drive a generator, though.
F150 has entered the chat.
In reply to 93gsxturbo :
Assuming you are talking about the F150 EV, it isn't a generator, it's a battery.
Toyman! said:
In reply to 93gsxturbo :
Assuming you are talking about the F150 EV, it isn't a generator, it's a battery.
No one talks about the F150 EV LOL.
I am talking about the F150 Powerboost (gas engine) with the 7.2kw generator with 120V and 240V plugs.
ShawnG
MegaDork
4/22/24 10:18 a.m.
Seems like a very inefficient and inconvenient way arriving a the capabilities of a little, 3000 watt quiet generator.
In reply to ShawnG :
I've actually wondered how efficient the generators are. They run fixed spark, meaning it's whatever WOT spark plus a bunch of safety is. If the car could be run slightly off idle, it would probably be more efficient, but at idle, it's running a lot of spark retard for control reasons.
What would be cool is if you ran electric control on the small engine, but allowing for the throttle govenor. Then you could run good fuel (even lean) plus good spark. Or at least run spark control.
I ran the diesel generator in my motorhome for about 30 hours this weekend. It burned 10-15 gallons of diesel.
For our next storm, I'll just plug the house into the motorhome. The onboard tank should run the genset for 150 hours.
In reply to Toyman! :
Toyman! Gets it.
John Welsh is exploring the possibilities of using something he ALREADY owns as a backup power source for his Fridge (in case of emergency)
