Well DONE!

Two things:

1) photos?
2) test your window AC at least once with the extension cord

Although my unit handles 1 kW with a 1.2 kW surge, I start by turning the AC thermostat to the warmest setting and the fan on low. Then I plug in the inverter. Once the fan is stable, then I turn down the thermostat to start the compressor. If your unit runs, you're probably OK although you'd like to monitor the compressor housing temperature to make sure it doesn't overhead. Do listen for any 'lugging' sounds.

If you can, test the circuit to see what the load measures and voltage to the AC.

Bob Wilson

 

For about $75 shipped off the Internet I bought a Motor Trend (probably not related to the magazine) 800W continuous / 1600W peak inverter. I think it's a modified sine wave inverter, and probably nothing particularly special about it except that it comes with a carrying case to hold the connectors and the instructions. Since I knew I would only be using mine on rare occasions, it was convenient to have the instructions and all the parts handy. Also I couldn't find one locally in the 800-1000W range, and I didn't want to go higher since some say there's a risk of fuse damage to the car above 1000W.

No photos, since there's nothing special to see except that rectangular inverter sitting in the trunk and an extension cord running into the house. Amazing how simple it is.

No luck for me on the window AC though. I used a Watt-meter to measure the power draw. The fan on low was only 70W, turning it to cool with the thermostat high was the same since the compressor is still off. But when I slowly turn the thermostat down, the inverter tripped off right when the compressor kicks on. It seems the A/C wants 420W continuous, and more at the start.

My A/C is 5100 BTU, 9.0EER, 115V @ 5.3 Amps, about the same as yours. Seems like my inverter would be OK for the continuous load, but either the in-rush is too high or the inverter is just sensitive on the overload switch.

If I knew a different brand or model of inverter might be better with the surge, I might try another one. Would a 800VA computer UPS in-line smooth out the initial draw, or would it also trip off in the same manner? Well in any case, I can still power a lot of compact flourest bulbs and small electronics with what I have.

 

One trick is to use a resistor network to bring the voltage to ~1 V and feed it into a PC line-input port. Use audio recording software, open source, to record signal and you can see what the voltage profile looks like. Piece of cake.

I'm seeing ~700 W. load when running the AC, which is why I encouraged the test. The modified-sine wave appears to require more power than regular line power. Still, you have enough power for some nice box fans . . . or look for a 1 kW inverter with a reasonable surge.

The photo I was interested in was your connection to battery.You're looking at currents of a little over 60 A. and any input lead resistance will easily limit your power. I may have gone overboard but I really wanted to minimize the (I**2)R losses.

If you've got a small, space heater, you can use it for a straight resistive load. Then you can check the 12 VDC connections to make sure there is no heating or appreciable voltage drop. But then, there comes a point of 'polishing the musket *****.'

Sounds like you have a good solution. Have a happy!

Bob Wilson

ps. Swamp cooler?

 

I noticed that Costco has a 1000w / 1200 w surge inverter for $30 in the store. Pretty sweet price for a Xantrex.

 

A couple of CAUTION notes...

Capacitor start and capacitor run AC induction motors do not take "kindly" to MSW "square wave" power. Some will not start reliably, some will not start at all. This "effect" can be even worse for AC induction motors that drive refrigerant compressors, like that 5000BTU window air conditioner.

It takes 1666 watts to generate 5000BTU directly, say electric resistance heating. Air conditioners are typically 3-4 times more efficient ("heating" the great outdoors) so it would take about 400 watts to run that 5000BTU A/C. That would be GREAT if my story, caution note, ended there.

But it doesn't.

The starting, surge, inrush, load for an A/C is typically 2-3 times the running current, 800-1200 watts in this case. And that's only for an initial start cycle for an A/C compressor induction motor. Sequential "starts" are often with refrigerant head pressure, raising the starting surge to at least 3 times the running current, or more, depending on the type of thermostatic control is being used.

And....

These systems MUST somehow split the single incoming power phase into at least two phases, some only for induction motor startup, but others for the entire "run" duration. ALL of the phase splitting techniques are designed, optimized for sine wave power input. Some induction motors will not start at all with MSW inputs and many that do start will only start after many cycles of their internal overheating automatic resetting CB's.

With the advent of so many HM/RV owners using these MSW inverters the industry has wised up and is looking somewhat askance at honoring warranties for failures that appear mysterious....

120VAC @ 1000 watts from 12 volts = 90 amps....

From that tiny 12 volt lead-acid battery...?? And for more than 10 minutes...??

Are we leaving the key on so the DC-DC down-converter can be continually "recharging" the 12 volt battery from the hybrid..??

Basically any load device that doesn't directly provide HEAT or LIGHT (from HEAT) will be running on/with a completely out of line, out of the ordinary, PF, Power factor, and will likely overheat and possibly fail due to operating beyond the manufacturers design expectations. And by the way as the power factor goes "south" as a result of reactive loads/loading, the 1000 watt rating declines...and declines...and declines...

Go to RV.NET for more....

 

Internal to these inverters is an DC-to-DC upconverter, via PWM and a voltage step-up transformer or system the 12 volts is upconverted to ~148 VDC. It would be much simpler if someone designed an inverter that used the hybrid battery voltage to begin with.

 

You are correct...

But the puzzling part is WHY...??

TONS cheaper, method vs purchasing a hybrid, would be to purchase two 6 volt deep cycle golf cart batteries to use in series, add a multiphase battery charger, and an inverter.

I would recommend a 3000 watt PSW, pure sine wave inverter.

Or $300 for a new briggs & Stratton or Honda powered 3500 watt genset.

 

The goal is to get a little more utility out of our Prius. Adding an inverter also provides AC power for laptops when going down the highway; and enough power to camp-out in one's home during a power outage.

Bob Wilson

 

Input....

Yesterday morning I got up to a cold and dark house and discovered our backup genset would start, but not pickup the load, and then shut down within about 30 seconds(***). While I was busy in and out of the COLD troubleshooting the problem my wife woke up and DEMANDED her morning coffee.

I have a spare car battery that I keep fully charged (always on a multi-phase charger) that I brought in, hooked an 800 watt MSW inverter, and plugged the coffee pot into that. I maybe got two cups brewed before the "beep-beep-beep" of the inverter started up, I had to "re-seat" the battery (spring) clamps and maybe got another cup brewed before the battery was below the tolerance of the inverter, 10.5 volts.

If a full size 12 volt car battery with HIGH starting current capacity cannot provide ~800 watts (~60 amps), for the 5-10 minutes it takes to brew a pot of coffee just how long will the 12 volt "low" current capacity supply more than 10.5 volts.

*** Intermittent spade-lug connection at the 10 amp regulator/field supply fuseholder.

 

I would think it would be more productive to add an IR motion sensor to automatically turn on the Prius' headlights(***) and thereby illuminate your home's entry-way as visitors approach at night.





*** Provided, of course, the headlights are of the low wattage, 35W each, HID type.