Best of Deals Car Reviews Repair Shops Cars A-Z Radio Show

Car battery Heat shield

Hi all,

apparently some cars, and more newer cars come with battery heat shields: a casing to protect the battery from the engine heat:

Is that truly useful?
DIY possible?
–> 6mm thick Aluminum foil + Muffler Cotton Car Indoor Heat Sound Deadening Insulation Soundproof Dampening Mat:

it’s flame retardant and heat resistant upto 105 deg C (221 deg F), but the outer aluminium means it’s conductive, so maybe not suitable to wrap the battery sides and bottom in it (leaving the top open obviously)?

They seem to use it to cover the inside of the bonnet, so I suppose heat wise it should be fine?

Reason is because in Thailand car batteries die rather young (around 1 year), and I’ve read that car batteries do not charge well when hot (anything above 55 deg C), so if the battery would remain less hot longer, it would get a better charge, and since the worst for a car battery is to lose 50% of its charge = dead battery.

Would be a cheap solution, but most likely not helping much since after some time the whole engine compartment will heat up eventually… also read that it could work the other way around: the battery will not cool down as fast after driving, keeping it longer at higher temperature…

so possibly those new cars have it for cold countries to help start during winter time?

The indoor in the description leads me to believe that product would not hold up against weather. You are right about heat killing batteries, I live bear the US/Canada border and my Camry’s battery is over 8 years old and the one in my daughters Corolla is 10 years old.

1 Like

The Checker company that made taxicabs put the battery in a compartment in the trunk to keep the battery away from engine heat.

You have it backwards. The blanket is there to keep engine heat away from the battery and thus keep the battery cooler.

1 Like

Its main effect is to slow down or reduce the heating up and cooling down of the battery. Given enough hours of engine heat on hot day, or of extreme cold while sitting, the battery will reach the high underhood temps or the cold ambient temps. The slowing of that rate of change helps prevent internal damage to the battery. That might help it last longer.

1 Like

The aluminum reflects heat so… that is a good thing. You have already stepped up to an Optima battery, if that is your car. The Optima, per a tow truck operator in Florida USA (hot, 40 degree C hot), holds up very well in the heat. The insulation should help and that is why many cars come with them from the factory.


Welcome back Mustangman.


My 1950 Chevrolet pickup truck had the battery under the passenger side floorboard. There was an access plate to lift up to service the battery. The location kept the battery away from the engine heat. However, I think the real reason was that it put the battery close to the starter. On that truck, the starter was operated by a foot pedal which closed the switch and pushed the starter drive into the flywheel. There was no solenoid or relay to go bad.

The battery in Miatas is in the trunk, supposed to be to help balance weight distribution. Maybe so, but the side effect is that it is far from any heat source. Mine lasted 17 years.

big thanks for all the replies!

no, that’s not my car, this is mine:

so right side of hood compartment, the air duct is covering it a bit.

and plan to use this material, stick it around the sides and bottom of the battery as a heat shield:

*Designed for sound absorption and heat insulation, can be used to keep warm
*Helps reduce noise, eco-friendly, perfect wall decoration
*High quality, waterproof and fire resistant
*Perfect for door, chassis, tail box, etc

*Recommended Install Temperature: -10 ~ +60 degrees Celsius
*Resistance Temperature Range: -40 ~ +149 degrees Celsius
*Material: Aluminum foil+Rubber foam
*Dimension: approx. 100x40cm
*Thickness: approx. 5mm

if it can be used under the hood it should be able to handle outdoor conditions, which means a suitable battery shield?

Since Bangkok is so much traffic, the car idling a lot… (=> no cool breeze to cool it down) so I believe it may be the reason why car batteries often only last 1 year in Thailand…

It doesn’t say anything about under hood,
And the MAX recommended temp is only +60 Celsius/140 Fahrenheit.

believe installation temperature they mean at the time you install, probably otherwise the adhesive won’t take/stick.

Resistance Temperature Range: -40 ~ +149 degrees Celsius

the 149 degrees C = 300 deg Fahrenheit is the operational allowed temperature.

It’s meant also for under the hood/bonnet, I could see it in the pictures on other ads as well, and there they list it also as application, here they don’t, but it’s mentioned in the title: “Car Bonnet Trunk Heat Insulation Sound Deadener Noise Reduce Foam Mat

I’ll ask what the rubber foam is made of exactly to cross check the temperature limit… but I’m assuming if the stickers on the battery don’t get scorched this material should also be able to handle it?

I am not convinced this will work as desired. Heat resistance does not mean it’ll completely block the heat. It means the heat will penetrate at a slower rate. The battery will eventually still get hot. And now that it’s covered in this shield - it won’t cool as well. Not sure how well this will really work.

Battery blankets for winter driving have been around for decades. They were designed to keep a battery from freezing in extremely cold climates.

The battery blanket won’t keep the battery from freezing in extremely cold climates. It will increase the time it takes a warm battery to get to ambient temperature which, if cold enough and the battery discharged enough, or water added to the battery not mixed thoroughly with the acid, could freeze it.

Anyone remember heated battery blankets or trays - plugged into house current? One of the many wonders in the JC Whitney catalog.

But the car battery will eventually get cold too, sames concept as about getting hot, which you refuted just a couple of lines above.

IMHO, for both scenarios, the purpose is to make that “getting cold/hot” scenarios to slow down.
Assuming you drive your car, not merely let it idle, it may help by slowing down the heat penetration when it sits idle, then on the speed it will get cooled by the incoming air.
For the cold scenario, it will only slow down the temperature drop, yet you have a chance it is few degrees warmer than the morning crisp frosty air around.

1 Like

I have doubts about the part saying batteries only last a year in Thailand . I could be wrong but it seems that air flow around the battery would be best in a hot climate rather then something that would keep the heat in .

I’m not sure I like the metal foil near a battery and its connections…

1 Like

Not to worry, it’ll be gone in a flash…


True…just prolongs the time. But one is for immediate starting (cold), and the other is for long term battery life (hot).

1 Like

O.E.M battery insulators are non-metallic, they have been in use since the 1970’s. The one below is foam and plastic. The one on my Dodge is like heavy duty bubble wrap.

With under hood temperatures of 160 to 180 F batteries do not cool while the vehicle is in operation.

1 Like