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
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A battery can freeze at 20 deg F if not well maintained. Here is a good articel that explaines how the electrolyte in the battery works. If the battery froze solid, there is a good chance that the case is cracked and you will loose all the acid when it thaws rendering the battery useless
http://www.edmunds.com/ownership/techcenter/articles/43835/article.html

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I like the part about push starting a car, because everyone wants to do THAT when its 30 below... Thank God I live in Arizona....
Interesting thing to note that is Off Topic: cars with breathalizers can be push started if they are manuals :D
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Paradox wrote; Thank God I live in Arizona.
August 2004 - Future Posting :
Paradox post's : Its 120 degrees here in the Arizona Desert & my battery won't start my car when its this hot? Why not?
: - )
========Harryface ======== 1991 Pontiac Bonneville LE, 3800 V6 _~_~_~_~276,100 miles_~_~_ ~_~_
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On Thu, 29 Jan 2004 20:33:37 -0700, "Paradox"

an electric fuel pump won't work. ...thehick
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You probably have a low Cold Canking Amp rated battery. Do you know what the Cold Cranking Amp rating is for your battery? It may say on the decal on the battery. If yours is a low rating of 550 or 600 your chances of starting a vehicle when its - 30 degrees out lessen.
My battery for example is a Sear Rangehandler 1000 Amp / 900 Cold Cranking Amp battery. I have the highest cold cranking amp battery Sears offers, so the chances of my car starting when its -30 below out are better than another car starting that only has a 550 Cold Cranking amp rated battery.
The article that 8 up posted should explaing the operation of battery & its functions...
Also its been + 4 degrees tha last few days, and with this battery I have, the car starts in 2 seconds.
========Harryface ======== 1991 Pontiac Bonneville LE, 3800 V6 _~_~_~_~276,100 miles_~_~_ ~_~_
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A fully discharged battery is, in theory, filled with water. Typically the lower the charge on the battery, the closer the liquid, chemically speaking, is to water and since water freezes at 32d F, that is why one will freeze. The better the charge, the less it is just water and the more it is electrolyte. This is really basic, but is a basic explanation as to why a discharged battery will freeze. Years ago my old instructor told me that, in theory, you could drink the water from a completely dead battery as it is basically water.......but you'd be a fool to do so because it is not quite completely water, but the closest it could be to it.
Patrick

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Pt3 wrote:

Remember this one:
Johnny was a chemist. Johnny is no more. What he thought was H2O Was H2SO4.
---Bob Gross---
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Yup, but that was the simplest explanation I could think of to explain a battery freezing. While you'd have to be a moron the drink it, it does help a little as to why it would freeze.
Patrick

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Another freezing way to explain the discharging and ionic interaction between the lead plates and H2SO4 and PBSO4 and H3O and H20 is water being released dilutes the liquid electrolyte and the hydronium ions diminish as a lead acid battery is discharging and thus raises the freezing point.
Maybe Johnny needs to concentrate on a water purification system!

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The acid has been neutralized, leaving water + a salt (in this case PbSO4). I would think the salt would make it non-potable.

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No, not really. It's simpler than that, actually. What is going on is that the electrons that charge the plates are motivated to flow through the battery when the individual electrolyte molecules react with the molecules in the plates. When the temperature drops, those molecules move slower, thus not as many per-second come into contact with the molecules in the plates, thus the battery peak current drops.
A battery produces electricity due to chemical reaction. When it's cold the chemical reaction goes slower, this is true for most if not all chemical reactions.
Ted
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I agree,chemical reaction is slower at cold temps , it helps sometimes to crank briefly then wait as the battery warms due to the reaction as well . Whatever you do DONT boost a frozen battery as they will blow up , burst and then you have serious medical probs as well ! proper maintenance and load test the battery , maybe its sulfated .

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