3 liter V6 drains 10 amps at rest, no smoke.

Here are sxome things to try:

Disconnect one or more circuits to isolate the problem (pull fuses or unplug things or whatever - do you have the vehicle schematics?) - IOW - disconnect everything from the main bus - you should have almost zero current draw from your charger with that. Then connect a circuit at a time until you get the high current draw again. That will tell you which circuit has the short.

It sounds like the battery is fried due to being severely drained possibly as a result of the original problem (a short). So now you have two problems - a short and a boat anchor battery.

What is the current rating of the charger you are using?

When you have the battery disconnected and you hook up the charger to the car (not the battery), what voltage do you measure?

The charger is going to put out its programed limit of current even if there's a dead short to ground in the car's main power bus - and that could very well be what you are seeing.

The 40 ohms you are reading may not mean anything because the meter doesn't try to force a very high voltage onto the wires to make that reading. It may be a non-resistive short. You may have something shorting out above, say 3 volts. I think the voltage reading with your charger hooked up without the battery will tell part of the story.

SUMMARY: (1) Isolate the circuits to see which one is shorted. (2) Measure the voltage at the charger output when it is connected to the bus with the battery disconnected.

Also - a test light (get it at you local auto parts store) may help in the isolation of the circuits to find out which one is shorted. With main fuses pulled, put voltage to the bus, then bridge the fuse holders one at a time to see which one lights the light - thats the circuit with the short.

It isn't a good idea to connect a charger to the car with no battery in place. Electronics like clean even power. When you hook the battery charger directly to the car with no battery you loose the inherent filtering capacity of the battery and battery chargers put out particularly nasty power because there is normally no need to filter their output.

Basically having the car on a charger with no battery will cause the electronics to go nucking futs and anything is likely to be happening. A battery that was at 5V did not charge back up in a couple of minutes. I would recommend that you fully charge the battery and have it load tested then put it back in the car. Give the system a little time for the computers to do what they need to do and see what the power draw is.

My hunch is that you have a battery that has croaked and once you replace it things will return to normal. I could very well be wrong though... make sure you test the actual current draw with the battery in the vehicle to see what's goin on.

Steve B.

You are correct about the filtering that a battery provides in the electrical system. But that still doesn't explain the 12 amps that the vehicle is drawing from the charger. Something is presenting a conductive path to ground for it to be pulling 12 amps with everything off.

I agree that the battery needs to be working (the one he has is probably toast due to being totally depleted and left that way for a time), but there is something that is pulling current - in other words, a short.

Internal short within the battery due to failure of one or more cells - mechanical failure vs chemical failure.