Hey John,

Do you know this for a fact?? I'm not doubting you, just wondering how you came by this info??

My 05 4WD FEH did not come with the optional DC/AC inverter so I installed one myself. I used a 400 watt aftermarket inverter that I installed in front of the center console & wired to a duplex outlet I installed in the side of the console. I wired the fused 12 gauge power wire directly to the 12v battery under the hood.

I wonder what happens when I run my setup without the ICE running?? Would it still use the HV power first????

~John

 

Hey John ( great name )!

Yes, I know for a fact because I've done it.
If you put a volt meter on your cigarette lighter, without the key you will get 12.2 to 12.4 volts.

Turn the key to "run" and the voltage at the cigarette lighter will be 13.9 to 14.4 volts, and it will stay there for a long time. ( The engine is not running, thus this voltage must be from the HV pack. )

At some point you will hear a relay "click". ( if you don't have the radio on! )
Instantly, your volt meter will drop to 12.2 v or something lower when your 12v battery takes over again. The "click" is the HV battery cutting off to save enough in reserve to start the car.

 

That's good info, I had been meaning to check it out myself with a voltmeter but haven't had time(I've been working WAY too many hours lately)

Obviously, if it jumps to 14v when you turn on the key & the alternator is not spinning, the current has got to be coming from the HV battery.

Thanks for the response...

~John

 

I drained the 12V battery more than once by leaving a laptop running and plugged in for the entire day while I was at work. With the key in off, the relay isolating the HV battery is open (for safety reasons for mechanics and firefighters). Once the 12V is too weak to energize the HV isolation relay, then you can't start the engine or even use the HV battery to charge the 12V battery. I never tried leaving the key in the on position to see if that kept the relay energized, but my guess is that it will still open the relay after about 20 minutes or so.

 

That's interesting info.

However, for something like a laptop, if you use the HV battery, you would have at least 10 hours of power.

I pulled 100 amps at 14v for 26 minutes once and was still able to start and drive away. If your laptop takes ( go high, 2 amps? ) you can see how long it would last.

Of course you can't leave your vehicle with the key in, or your car may be stolen!

 

I have a silly question. In the "old" days, I was told not to leave the ignition in the "on" position unless the engine was running to prevent the risk of burning the rotor in the distributor (if it happened to be sittng on one of the spark plug contacts). I assume this is an electronic distributor, but is there any analogous issues with turning the key to on without starting the motor (to at least give the computer a chance to control the ICE and turn it off in it's own way)?

Cheers,

Roch

 

The problem then is that the computer will then keep starting the ICE to keep the cat warm every few minutes. It would also keep the battery charged but not the ideal situation for most of us.

 

Not to mention the danger involved if you forget it is on and go to do something under the hood. The ICE can start without warning.

 

Now that we know it's a "fact" that the inverter runs off of the 300V battery and not the 12 volt battery, I wonder what it would take to set Ford straight on this and get them to change their erroneous publications? Apparently they're not aware of how the system operates since section 414-05-1 of their own service manual states the converter runs off of the 12 volt system. Sections 12 and 13 of their wiring diagrams also show it running off of the 12 volt battery.

It's no wonder their mechanics don't know as much as we do here!

 

I don't think they are in error, I believe the AC inverter for the AC outlet on the console runs off 12V (there is a 30A 12V fuse for it). There is DC/DC converter that runs off the HV battery to make 12V, but I don't understand its entire purpose yet. Or am I wrong again?

YMMV, Don