DIY Battery insulation

Well we’ve had some frigid weather here in the NE (14 degrees as I type) and I noticed my car’s batteries don’t have any insulation material or container… I was wondering if I could DIY it with some 1" fiberglass insulation, the kind for heating ducts with mylar on the outside to reflect heat in summer.

Any potential problems with doing something like that?

They don’t have any insulation because, one, they’re designed to work to ungodly low temperatures, and two, even if they had insulation, there’s no internal heat source, so there’d be no heat for the insulation to trap in. If anything it would keep the engine heat away from the battery, warming it less while you drive with the net result of a colder battery.

The battery in my 2000 Blazer has an insulating blanket, but it is to protect the battery from engine heat.

Ed B.

I agree, the only way to have a warm battery on a cold morning is to have a heater and/or tender charger on the battery. On my old diesel, I have the block heater, the battery heater, and the tender charger all wired to a single plug that I can use in very cold weather. Of course, that only helps if you are someplace where it can be plugged in.

There’s one other way. When I was nursing a weak battery on my old '76 Chevy Pickup, I got in the habit of bringing the battery inside with me. Of course, this battery was held in with a bungee cord and would start just fine with finger-tight battery connections, so it took me about 15 seconds to take it out. It probably got me another month or so out of it before I had to face facts and start sharing the battery between the truck and my old Buick. I know today I have arrived in life because I have the same number of batteries as cars!

Your story about “nursing a weak battery” reminded me of a time years ago when I nursed a battery on my 1968 Ford. My fiancee and I were in Montreal during a cold snap and my car wouldn’t start. I ended up taking the battery out and letting it sit in a bathtub with warm water for a few hours (made my fiancee wonder what kind of guy she was about to marry). Warming the battery was enough to get it going on a subsequent retry. I too know I have arrived in life because I don’t need to do many of those similar hacks on my cars as I did years ago.

If it doesn’t get down to minus 25F, it isn’t cold. If your battery is dead at plus 10F, you need a new one anyway. Oh, the problem is fire.

I think the only reason you see insulation around batteries is to protect the battery from radient heat from the engine. A batery that passes a properly done load test could probably start a car at -50 degrees F. if fuel/compression/ignition is OK.

Why do you need one??? Never heard of it…and have no idea why it’s even needed. Batteries are designed to work without it. Save your money for something that’s really needed.

There is insulation covering the entire engine compartment via the hood, is a thin layer wrapped around the battery really a fire hazard?

A lot of cars come with battery blankets pre-installed. It seems the primary reason for them now is to protect against heat but I’m wondering if blocking wind chill could also be a factor. I know wrapping home heating oil lines with insulation is common practice for a similar reason. Just wondering.