Inverter on 12v battery

In all the threads on running a 1kW inverter from the 12V battery no-one has reported any problems with the DC-DC fuse nor with the car wiring.

 

I don't have a GenIII so the 10AWG is going off of what you said.

 

I'm sorry for your problems and 10 gauge is way too small: American Wire Gauge
table and AWG Electrical Current Load
Limits with skin depth frequencies and
wire strength

• chassis wiring limit, 55A * 12V = 660W max!

I'm going to recommend going to WalMart, automotive section and shopping for 6 gauge, 12V cables with swagged ends. Rated at 101A * 12V = 1212W, this will provide the minimum head room for your installation and the commercial connectors will help a lot.

Look around for an adjustable heat source including an iron, hot-plate, hair dryer, or a high-intensity light. If you go by a hardware store, you can pickup a dimmer rated up to 250W, a light socket on lead, a 200W heat lamp, a 15A extension cord, and a wall-box. Just rig up the dimmer and extension cord so you can adjust the output voltage. Then plug the lamp into the extension cord. Put 500-600W on one inverter outlet and confirm everything is working. Then add the adjustable load on minimum setting:

1. Measure 12V voltage at battery connection. If it starts to drop below 12.8V, stop the experiment, that is the maximum, sustained, 12V load!
2. Run for 1 minute - carefully touch test the 12V cable at the connectors to feel for any heat. If hot, stop and properly reconnect the 12V cable. DO NOT OVER TORQUE!
3. Verify the cable itself is cool to touch.
4. Verify the inverter is not hot, verify where the heat is dumped.
5. Increment the load, repeat steps 1-5.

Bob Wilson

 

I have successfully tested such setup (connecting to the 12V battery pictures in the other thread) and found that TV lights were fine but the fridge tripped the inverter 1000W (2000W surge) pure sine wave. The compressor motor in the old fridge just too much inductive load.

I have not used it continuously ... but remember some members did can someone comment who did use it for some time?

I do understand the concerns 2K 1Toster but this is just theory at this point. btw I fused the input cable to inverter 85 A so I am not even trying to get 1KW. But hoping to run internet TV and hopefully the water pump of the heating system in emergency.

 

We run it at least once per year but in April 2011, we ran 4 days and 6 hours.

Prius - UPS Project

We have a similar setup using a sine-wave inverter rated at 1.5kW continuous. I've tested it up to ~960W only to find the 120A, 12V circuit breaker and the Anderson connectors lose too much power. I am confident we can go to a sustained, 1kW once I take them out of the circuit.

Bob Wilson

 

So if I understand this you were running sustained using the chassis wiring to the 12V battery without "melting" that ...

And also others run similar setup. Final good solution when Toyota decide to provide OEM next to the 12V port seem to be a 120V size plugged opening in my 2012 Prius

Yes 1KW over 12V even small resistance is brutal as I said my goal is more 750W top with this setup.

 

I'm pretty careful about my wiring, especially power wiring. I'm a great believer in using non-contact thermometers early and frequently. We can't 'see' heat and you never want the smoke to escape.

Bob Wilson

 

Just a couple of load related things to consider:

• Inverter surge - typically ~300 ms., 15-20 cycles, this is the inverter peak power rating. So my 1500/3000W inverter can provide power up to 3000W for a couple of hundred milliseconds IF the 12V supply can provide the current. If the battery bank is large enough and the conductors heavy enough, 3000W/12V ~= 250A. This is within the 'cranking' amp range of even our 12V battery yet brief enough the cables won't melt . . . but a fuse.
• Load inrush - typically ~300-600 ms., this load can trip the 12V low. Many electronic power supplies including laptop power-bricks, are bad about having a diode bridge feeding a large capacitor. The inrush can be so bad that the plugs arc just plugging them in without a load! For this, I've used an inrush thermistor that starts high resistance but as it warms the resistance drops. The problem is the thermistor has to stay hot and that wastes power.
• Motor startup - typically 1-3 seconds, this load can trip the 12V low. Induction and synchronous electric motors found in compressors and furnaces often have a somewhat complex startup load. If the 12V battery and cables are already running high loads, this can trip the 12V low circuit.

I once left the house with the lights, an inrush risky TV and cable box, a box fan, all running on the 1.0/1.2 kW inverter. While I was out, something triggered a fault and the inverter and load went into a 3-5 second, loop: all on; 12V low trip, and; auto-reset back to all on. I thought it was funny but my wife did not appreciate the humor.

I simply disconnected the inrush load, minimized the other loads, started the fan to get it running, re-connected the inrush loads one at a time (laptop, cable box and then TV,) and added the rest of the loads.

When you realize how startup and inrush loads, you can 'camp out' at home. But it helps to test with the loads before a real outage. That is not a good time to be testing.

Bob Wilson

 

I would like to see how you ran wiring from battery. I trial ran some
#8 wire, also got a deal on a 1000W used inverter. I'm planning on
using to charge RC plane batteries, instead on transporting heavy 125
amp hour deep cycle. Also will use a power back up, just to run gas fireplace
fan, TV and a few lights. <500 watts I also plan on maxi blade fuse 80 amp
near + terminal.

Advise gladly accepted, Thanks

 

Thanks for sharing the details of this set-up. I am looking forward to the pictures. Are you planning a quick connect/disconnect?

 

Thanks for the helpful video! Nice install!

 

Hm, old thread I didn't see at the time!

That fat white wire going to the single plug is not the one from the converter; that is in fact the wire back to the 12 volt battery itself. (Unplug it, when the car is off, and things will all go dark.)

If you look just to the left of where that plugs in, there is a kind of square cover set diagonally. That cover can be lifted up if you squeeze the right things, and underneath it there is another fat wire ending in a zany spade terminal clamped under a nut. That is the wire from the converter.

In between those two is the 125 amp "DC/DC" fuse. It is a royal pain to get to. It is bolted to the front of that largest module making up the fuse box. You have to take the box apart, as detailed more here.



That white integration relay replaces a number of other smaller fuses (such as for the low-beam headlights, horns, etc.) with non-fuses ... the thing's electronic, and apparently has some self-resetting current limiting built in. But the big 125 amp fuse is separate.

A lot of posts in this thread are using ampacity tables for household wiring. Ampacity isn't a fixed property of a certain thickness of metal wire, but a function of how much heat that wire will produce, what temperature the insulation on it can handle, and how well heat can get away from it.

Household wiring typically uses fairly low-temperature insulation. For example, 2k1 refers to 60 ℃ wiring here, which is low even by current residential standards:

House wiring you can buy at the local big box has been more likely to say 90 ℃ for some decades now.

Automakers routinely use wire gauges that seem insane by residential ampacity tables, because they use wires with insulation ratings that can be 125 ℃ or 150 ℃ or so. And are generally not surrounded by insulation blown into the walls of a house.

Whatever gauge is that fat white wire from the front to the back of the car, given that Toyota put a 125 amp fuse on the front end of it and a 140 amp fuse on the back end, somebody signed off there that it isn't going to turn into a string of dripping goo at 125 or 140 amps. Your main concern will be voltage drop, just figuring out what voltage you will be seeing at the point where you've tapped off, when pulling the current you expect to pull.