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Living in the north, I am wondering if a sitting car battery's chemical reactions give off enough heat to justify insulating it. That is, will it result in significantly more power available to start a cold car?

[I did ask that this be moved to the engineering forum]

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    $\begingroup$ Without current flowing there should be little going on inside a battery. Various lithium batteries incorporate a heater to maintain output in cold conditions. $\endgroup$
    – Jon Custer
    Commented Sep 18, 2023 at 13:30
  • $\begingroup$ "incorporate a heater" Interesting - I had no idea. $\endgroup$
    – Mark4362
    Commented Sep 18, 2023 at 18:57
  • $\begingroup$ yup - some batteries have it self contained, or you can get a heater jacket. The available output drops by about 50% going from 80F down to 0F so if you are winter camping, ice fishing, etc. you want to keep things warm. The small amount of power used more than makes up for itself in additional power available. $\endgroup$
    – Jon Custer
    Commented Sep 18, 2023 at 19:05
  • $\begingroup$ Qmechanic, good morning. Probably the first since it concerns the practical application of electronics and chemistry in a motor vehicle but I'm new here so you can decide. Thanks! $\endgroup$
    – Mark4362
    Commented Sep 19, 2023 at 13:01

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A lead-acid car battery sustains chemical reactions only while current is being drawn from it or injected into it. In general, a warm battery can deliver more cranking amps than a cold one, but as soon as you start drawing heavy current from a cold battery it will warm itself up due to its internal resistance.

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  • $\begingroup$ I had thought that because a sitting battery will drain if not recharged that there was activity. Thanks for clarifying. The insulation may still help once the key is turned or as suggested elsewhere the lights are briefly turned on which draws current and warms the battery somewhat. $\endgroup$
    – Mark4362
    Commented Sep 18, 2023 at 18:54
  • $\begingroup$ The voltage is a function of temperature; keeping it warm in cold conditions will have more power available. $\endgroup$
    – blacksmith37
    Commented Sep 21, 2023 at 15:28
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Note that batteries, including lead-acid and Li-ion batteries, are most susceptible to overheating while charging. Any jacketed insulated battery should be equipped with temperature-regulating charge control.

Temperature-regulated charge control is standard for good Li-Ion systems, but not common for Lead-Acid automotive start batteries.

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