Ren Tescher, thank you kindly for this information.

I am going to hard wire a trickle charger ( 11/2--2Amps)
across the battery and when the weather is - 25C or lower
and I plug in the block heater, I will also plug in the
trickle charger which will pass current through the battery
and hopefully start the vehicle.

Thanks kindly
Denny B

"Ren Tescher" wrote in message
...
It is imperative that when starting a car in very cold
weather that the headlights be turned on for 2 minutes
BEFORE trying to start it.

An engine in cold weather due to shrinkage of metal
and stiffness of the lubricating oil increases the
starting load a battery 'sees' by several hundred percent.

As others have mentioned, a cold battery has less
chemical action to produce electricity.

So at cold temps, your battery is only putting out
maybe 30% of its capacity, and the engine is three or
more times harder to turn over!

So other than bringing the battery or engine indoors
to warm up, what can be done?

Headlights are a lower load, and are variable as well
(they will glow dimly on weak battery).
And as electricity flows through something, heat is generated.
This is true for a battery as well! (yes, current doesn't
just flow out of a battery, it flows through it as well)

So while the headlights are dimly lit, they are slowly
warming up the battery.
You will notice during cold times like that, the headlights
will start to glow a dull orange, and after a couple of
minutes, they will be shining brightly. That is when you
attempt to start the engine.

If you don't let the headlights do their work,
the battery will never have a enough juice to start the car,
the starter will discharge the battery and it will not warm up.

Ren Tescher
formerly of North Dakota

Denny B wrote:

A battery that is perfectly good why when it is -30C
won't it start a vehicle.
Please note we are referring to a perfectly good battery
and a totally functioning car.
What is happening to the battery that it cannot crank
the starter fast enough.
Chemically something is happening inside the battery.
Is it the electrolyte that freezes and chemically do what
it should do? Does something happen to the lead plates?
Does the 12 volts drop to a lower voltage? Does the current
output of the battery drop?

The cold is doing something to the battery What Is That
Something?
Well informed auto mechanics please step up to the plate!

I do not need to start my vehicle my spare battery connected
in parallel with the frozen battery does that.

If your frozen battery won't start your vehicle and you remove
it and take it indoors and let it heat up to house temperature,
after reinstall it on the vehicle' it will then start the vehicle.

What is happening to the battery internally at -30C?

Denny B