Battery shield

Is the Chrysler turbocharged? Turbos raise the underhood temperature pretty considerably. If it’s anywhere near the battery you’d definitely want to shield the battery from its heat, Not nearly so much of a problem with normally aspirated engines.

no turbocharger. 3.8L V6

It’s also possible that in the Chrysler the proximity of the battery to the engine’s exhaust manifold makes a battery shield necessary. I haven’t checked, so take his comment for whatever it’s worth. It comes with a money back guarantee.

Possible in the sense of effect from the exhaust, but eyeballing it, the battery is closer to the engine and exhaust components in the Toyota than in the Chrysler.

…except metal conducts heat. It’s typically a poor insulator.

Isn’t a cat’s heat shield made of sheet metal?

Yes, but it’s made to absorb and dissipate heat into the passing air stream, not to insulate against its transfer.

Aluminum is also an excellent metal for absorbing and transferring heat. It’s used in countless applications such as “heat sinks” for electrical equipment, as well as engine components, blocks, and heads, where the goal is to get the heat to be absorbed by the item for dissipation into a cooler media, such as passing ambient air.

Insulators prevent heat transfer rather than absorb and dissipate it. They do not readily absorb heat, leaving it in the item that they’re insulating. It’s a totally different goal.

Ceramics are particular interesting in this area. They’ll absorb and retain an enormous amount of heat, dissipating it only very, very slowly. The heat shields on space vehicles that have to transcend the atmosphere and return to earth are ceramic. They’ll get extremely hot without damage, and retain the heat rather than transfer it to the vehicle. They’ll dissipate it only very, very slowly, well after the vehicle has landed safely.

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Jaguar XJ6’s in the mid to late 70’s had a Lucas electric fan to cool the under bonnet battery. The battery may have lasted longer, but the fan, not so much.

It is, but it doesn’t sit right up against the catalytic converter. There is space between the catalytic converter and the heat shield.

The battery insulator has little effect on how warm or how cold the battery can get. It is not perfect insulation, so on a long drive on a hot day the battery will get as hot as the ambient temperature under the hood; left for a day or so in subzero temperatures, the battery will reach those temperatures.

The insulator’s effect is to slow down the rate of temperature rise and fall. Maybe that has some positive effect on battery life - slower expansion and contraction of the various materials in the battery, and their connections, for example. And for shorter drives, the insulator keeps the high underhood temp from thoroughly heating the battery. Heat, more than cold, shortens the life of car batteries.

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My view is that a shield made out of some sort of heat tolerant bubble wrap plastic should do no harm, and could well explain why the shielded battery lasts a bit longer than the unshielded one. The heat cycling under the hood is a tough environment for the battery. My Miata is 16 years old and still has its original battery, which is located in the trunk. I rented a Chevy sedan a few years ago and found the battery in the trunk, too.

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@wentwest … 16 years on the same battery? That’s pretty good. I’ve never got more than 12, and that only on my truck which is driven only a couple of short trips a week. On my daily driver Corolla, about 6 -7 years is the most I get on the same battery. How often is your Miata driven?

I agree that keeping the battery cool as practical should be helpful to battery life, but I’m not sure putting it inside a shield – metal or plastic – is the way to do it. The reason is b/c the battery itself creates heat during the charging and discharge process, so best to allow that heat to escape.

You make a good point. My car batteries last four years because I live in a hot climate, not because of how hot the engine compartment gets with the engine running, so surrounding my battery with insulation of any kind seems like a fool’s errand in light of your profound insight.

Folks, think heat soak after the motor is shut off.