A sticker near the door inside a car said:

Exposing a battery to intense heat may cause deterioration. Do not bake over 158F/30min or 176F/20 min in painting.

I understand the first sentence, however, I can't see how words "bake" and "painting" are relevant in the context of batteries, can someone help clarify?

I can assume "bake" could be meant here as: "subject (something) to dry heat" and not baking as in a cake, but "painting" is still unclear.

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    @Lambie So it says in another way: Do not subject car to dry heat over over 158F/30min in general, and in case you are painting then do not subject car to dry heat for 176F/20 min, am I right?
    – john
    Jan 20, 2023 at 18:31
  • I admit I do not know. I can't imagine it's about painting the battery. "in painting" for me is when you paint your stupid (and my stupid) car. Haha, There are two temperatures for different amounts of time.
    – Lambie
    Jan 20, 2023 at 18:32
  • @Lambie the higher temperature has a shorter time limit. What the quote is saying: you can damage the battery if you exceed those limits when baking a (bodywork) paint job. The whole car is baked in a giant oven. Jan 20, 2023 at 20:04
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    @Lambie sorry, you were all "imagine" and "stupid" "Haha" and "I do not know". Jan 20, 2023 at 20:11
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    Wouldn't one just remove the battery before baking? Jan 21, 2023 at 3:16

4 Answers 4


When you paint a car you bake it in an oven so the paint will dry faster, which prevents running.


The sentence is a bit terse.

Do not bake over 158F/30min or 176F/20 min in painting.

This can be rewritten.

If you repaint the car and are heat-drying the paint, do not expose the car to continuous heat of 158F for 30 minutes, or 176F for 20 minutes.

These specific numbers seem like guidelines, and it would be up to the user to determine values for other minutes or temperatures. Exposing the car to that amount of heat would damage the battery.

  • It is still a bit unclear, can you explain in simple english maybe what the quote I brought means?
    – john
    Jan 20, 2023 at 18:32
  • I've added comments. Painting or not, don't bake the car in an oven too hot / too long. I guess it seems incomprehensible to some that one would bake a car, but it turns out that people do that when painting it. The painting just gives a likely context, not a requirement.
    – jimm101
    Jan 20, 2023 at 19:03
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    Bear in mind that baking a pastry or cake is not "faster than leaving it to dry". It causes something quite different to happen, and here it cures the paint. Jan 21, 2023 at 9:56
  • @WeatherVane some paints can cure slowly at ambient temperature or faster in an oven. When my van was resprayed a few years ago we had the choice - and as I recall the baking temperature was 80°C (matching the 176°F). It's the only time a vehicle is likely to be heated so hot; even leaving it in the sun all day in a desert probably won't heat the battery so much.
    – Chris H
    Jan 21, 2023 at 11:21

To bake:

to dry or harden by subjecting to heat.


The fresh paint on the car is dried by a process called baking.

  • Then why does it say: "Do not bake over 158F/30min"? Suggesting that you can bake it also without painting? (see the or)
    – john
    Jan 20, 2023 at 18:34
  • @john - nature.com/articles/srep00481
    – Gio
    Jan 20, 2023 at 18:36
  • Thanks I will have a look, but what is confusing me you suggest baking is a method to dry paint, if that's how it is used in the quote, why does it mention baking also without painting. The first part of the quote ("Do not bake over 158F/30min") suggest baking without painting. You see what confuses me?
    – john
    Jan 20, 2023 at 18:38
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    @john I don't. The guys applying paint know they have to bake the car, and they are told the maxima which are that temperature and that time. What the question's quote is saying: you can damage the battery if you exceed those limits when baking. Jan 20, 2023 at 20:01
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    @john — There is not baking without painting here. In [when] painting [a car], do not bake [the car] [at a temperature of] over 158F for 30 min or 176F for 20 min. Jan 21, 2023 at 4:10

You're separating the parts of that at the wrong place.

What it's saying is "You should not bake (when painting) for longer than 30 minutes at 158F, or for more than 20 minutes at 176F"

It's a question of 'degree-minutes' not to be exceeded, with fewer allowed at higher temperatures


The phrasing is a bit odd. I think it might have been written in another language and then translated, imperfectly. Or else it might have been written in English first, but by someone who was not a native speaker.

1. Why “in painting”?

The oddest part for me is “in painting”. I take this to be a shortened form of “in the process of painting the car”. I would find it more natural to say “when” rather than “in”.

2. Why “bake” a car?

I’m not an expert in car painting (or anything to do with cars, really), but I think that “bake” is a common term for the process of heating the car once paint has been applied. This certainly helps the paint to dry faster. It may also cause some chemical change that wouldn’t occur in air-drying; a Google search shows some references to catalysts, supporting this idea.

As Jim Mack’s answer says, the sentence needs to be read with the “or” giving two limits, both in the context of “Do not bake … in painting.”

So it could be rewritten like so:

When painting, do not bake over these limits:

  • 158°F for 30 min, or
  • 176°F for 20 min

3. How does this relate to the battery?

This warning is telling you what limits to observe if you bake the car with a battery still in it. I don’t know if it’s common practice to leave the car battery in while baking the paint. Even I know how to remove a car battery!

But perhaps it’s not only about the car battery, the big one that runs the starter motor. The warning could be about batteries that might be present in other car systems. These batteries might not be so easy to remove.

You don’t say what sort of car it is, so it could even be a hybrid or electric car, with batteries that power the engine. I have no idea whether those batteries are easily removable. (Another Google search suggests the answer is no.)

4. Nitpick: Why a slash?

The use of a slash between temperature and time also bothers me—slashes should mean “per”, but this isn’t a rate. It should instead be read as “for [a duration of]”. But this is something even native English speakers do. I’m only noticing it because I tend to nit-pick, and I’m a Maths teacher by profession.

  • If the car is a hybrid or electric vehicle, removing the battery might be much more involved than you think. Sure, there's a 12 V battery to run all the usual 12 V stuff, but there's also the giant 300-odd volt battery that powers the motor. That one doesn't come out easy.
    – Hearth
    Jan 21, 2023 at 6:43
  • @Hearth I don’t doubt that it’s an involved process, but I would dispute it being “more involved than [I] think”… simply because my best guess as to the process of removing an EV’s battery is “Step 1: Nope.” ;-) Jan 21, 2023 at 14:22

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