Why Won't a Frozen Battery Start a Vehicle.

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

Roughly 1/29/04 18:34, Denny B's monkeys randomly typed:
> A battery that is perfectly good why when it is -30C
> won't it start a vehicle.

Essentially your battery doesn't like cold much better
than you do.

Several things. The two big ones are that the power
from the battery is due to a chemical reaction. That
particular chemical reaction, like most, slows down
at lower temperature. The other issue is that the
battery will freeze at -30C if it is *roughly* only
60% charged. If frozen, the battery still can produce
power, but not enough to internally warm up the battery
or turn a starter in cold engine oil.


> Please note we are referring to a perfectly good battery
> and a totally functioning car.

Which may or may not be keeping the battery fully
charged to 100% charge, particularly if not driven
long enough. As the charge on a battery goes down,
the freezing point comes up...and the chemical
reaction producing power goes down. Street batteries
at 100% charge will freeze in the -40 range or so.
With the addition of a bit more concentrated sulfuric
acid, you can extend the freezing point down to about
-70C.

A trickle charger on the car overnight works for many
reasons...it keeps the battery fully charged, but also
the very slight heat produced by the chemical reactions
in charging keep the battery a bit warmer.

You can also get thermal wrap blankets and tops for
your battery for some makes... or afermarket.


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