Installing 1200W inverter, inline fuse, new wire

Most recommend no more than a 1,000 watt 12v inverter. You absolutely need to fuse it. Size by inverter recommendations. You will have to wire directly to a 12v battery assuming you use a 12v inverter. The better installations are similar to rv setups with an extra 12v battery and isolation.

Typically 12v inverters in this power range need free air cooling. So don't hide them too well.

The last thing you want to do is blow the 125a fuse located inside the engine fuse box. It protects the car's high voltage and dc to dc inverter which is where most of your power will come from. If it blows the vehicle won't run and access is difficult and time consuming.

 

You'll regret getting such a small inverter. Get at least a 2000 watt unit. I draw 2,000 watts continuously for hours without damaging anything. 1200 watts isn't enough to run a fine Italian cappuccino machine. Who could start their day without a fine cappuccino machine

 

It should.

 

Hello, I'm confused, are you saying you run the 2000 watt inverter with wattages near that capacity on your regular 2010 Prius? I thought the prius wasn't able to do much more than 1000 watts because of the fuses etc? Do you only have one starter battery attached to your setup as well?
Thanks for the help!

 

Yeah, something doesn't add up. 2000 watts at 13.8 volts is 145 amps.

The car's DC/DC converter is rated 120 amps, and there is a 125 amp fuse on the path from it to the battery in the back.



"continuously for hours" suggests a steady state where the converter is supplying power equal to the load. But the picture here splits into two possible cases:

• The converter really is supplying power at the rate being drawn, even though that's more than 20% beyond its total capacity (which also has to power the car), and at least 16% above its fuse rating. You can do this continuously for as many hours as it takes to blow the fuse.
• The converter isn't supplying power at the rate being drawn, and the balance is coming out of the battery (or batteries, if you have added an extra). You can do this continuously for as many hours as the battery charge holds up.

 

I use it at the racetrack where I power up a set of tire warmers the giant fan which is the size of the interior of the car and a coffee maker in the morning. I don't run the fan and the coffee maker at the same time. I have a 2000 watt inverter and all the lights go to max sometimes and it's around 80% of max much of the time. I wouldn't have enough power for what I'm doing I've had a smaller inverter. Not sure why but I'm not popping any fuses in the car

 

It does not hurt to have a 2000 watt external inverter if you don't use all the capacity. You then have better power semiconductors and better thermal management.

A true 2000w ac load will draw about 185 amps from a 12v supply or around 140 amps from a 14.5 v supply. These numbers include 10% conversion loss. The Prius dc to dc inverter/converter can't feed more than 125 amps without blowing a fusible link. Luckily the Prius dc to dc will current limit to protect itself. Effectively it shuts down.

There are vehicle current requirements while in Ready, so an external system draw much over 100 amps has to come from the vehicle's 12v battery which would then lose charge and voltage fairly quick. It is conceivable that a high efficiency 1500 watt dc to ac might run off the Prius while avoiding a 12v battery discharge.

Bottom line, a high current draw feeding a fully loaded 2000 watt external inverter would discharge the vehicle's 12v battery and lower system voltage in short order. Which is the reason a second 12v battery is added along with a battery isolator on RVs and trucks where large loads or off state 12v requirements exist. Typically they use a second deep cycle battery with larger capacity than the small Prius battery.

 

This cheap little 2000 watt inverter I got from harbor freight has low voltage alarm which doesn't alarm when I use it so for some reason I'm not draining the 12 volt battery down. Unfortunately it's a modified sine wave I'd rather have a pure sine wave. Next time that's what I would get

 

Yeah, sine finally came down enough in price that "modified sine" (which could more fairly be called "modified square wave") is hard to justify anymore.

 

Do you have a guesstimate on how many watts the car would be typically pulling in "ready mode" if you have everything running at the lowest settings?
Does the air conditioner/heater/defrost, brakes, or radio pulling from this 120A circuit? Or are those a separate circuit? If not, is there a way to completely shut off the the radio /navigation system? I thought I had it shut off before but my Bluetooth kept connecting to it, so maybe I didn't shut it off properly and only turned off the screen.

The answers you and @ChapmanF have given all over the board have been a lot of help when I installed my inverter. And I know I've read the answer to this a long time ago but I don't remember the terms necessary look it up.

Thank y'all!

Edit: Just saw ChapmanF's comment elsewhere "specified output of 120 amps tops, 30 or 40 of which are needed by the car itself"

BTW I took both of your advice on getting the 1000 watt pure sine inverter and then the 700 watt Instant Pot and I was wondering if y'all had found a Air Fryer that would work at these levels?

 

It was discussed several times on this forum:
-in Ready mode car needs about 12A minimum from DCDC converter just to power itself (all its computers, dashboard, etc). It may go up to 20-25A in case car needs to run radiator fan and electric pump
-air conditioner/heater/defrost, brakes, or radio pulling from 12V line from the same DCDC converter
-in regular car you have alternator (usually 120A) which powers all 12V devices. In Pruis you have DCDC converter (125A) which acts like alternator and powers all 12V devices
-yes, you can put any inverter you like, like 10kW, but you must always check real power consumption and keep it below 1000-1200W.
-If you draw too much power you will get inverter overheat and shutdown or in extreme cases blown fuse which is royal pain to access.
-power line from DCDC to 12V battery is designed for a 125A, in prius 12V battery is not a starter battery
PS: gen 3 dcdc inverter usually keeps higher voltage - you can use not 12V but 14.3V for your math
PPS: if you need more power, you can search about replacing oem 12V 45Ah battery by 100Ah or about adding second battery.

 

Just a side note, I haven't popped any fuses yet and the low voltage alarm hasn't ever sounded. I have a 2k inverter that I max out from time to time

 

Until we find out that douglasjre has reinvented mathematics, we'll probably just have to conclude that this maxing-out of the 2k watt inverter just hasn't happened yet for longer than the blow time of the 125 amp fuse at 16% overcapacity, or long enough to shut down the converter at 20% overcapacity.

It would be interesting to monitor the converter's IDH output at those times—that's the signal it uses to say "uncle! please turn something off!".