If a person were to start their car up (with a brand new battery) and let it idle for over half an hour in very cold temperatures (20+-4 degrees). Should that battery go dead?

If it does, is this an indication of a bad generator? I am for certain that no other lights or electronics are on in the car while it is off.

This may help with another problem, or may be completely unrelated.

Thank you.

 

OK,

The "new" battery may not be "fully" charged, it may have a "shelf charge" in it, which is more than enough to start and operate the car, and the alternator (generator in old terms) will take care of further charging eventually.

The running of the engine WILL charge the battery, IF the alternator is operating. Best check is a digital volt meter across the battery terminal and it should read "around" 14v engine running, even at idle. If this is the case, the alternator is deemed to be working.

Mine is 14.2v at idle, NO accesories on, and 13.8v with a/c, headlights on, all at idle.

A 1/2hr running without alternator charging would probably flatten the "new" battery enough so that it will not start the car.

I would put the battery on charge overnight, and then with it fully charged start the engine, do the meter readings, and let us know, it may an alternator with diodes shorting to earth and killing the car???.

 

Grant is correct if your volt gauge is showing 14+ volts get a multimeter and check the same on the battery, if it reads 13.8 to 14.2 I would say the altinator is working. You may have to find out what the battery loss is when stopped. Even when a newer car is off it still has things going on that will use up the battery. With no load and the neg terminal off the battery get a 1 ohm 10 watt resistor have one end of it on the batteries neg post the other end on the ground then clip a multimeter on each side of the resistor and read from the 20 volt DC you should have way less than 1 volt draw. If it's greater than that something is on. A draw from the dome lights is 2.5 volts. If you find it to be high then start pulling fuses untill it drops back. But then again it might be that the battery just isn't charged enough...

 

Currently it is a balmy 9degrees F, -13 C. I have the battery on a charger and will try to do some more work tomorrow, though it doesn't appear that it will rise much in temperature.

I will test everything I can as the weather allows and report back forthwith.

I need a heated garage with a lift. Anyone want to come build me one?

Peace!