why can't you set a car battery on concrete

[VonJayla]

The idea that you can't set a car battery on concrete is a persistent myth, but for modern batteries, it's largely false. The concern originated decades ago with hard rubber casings that were porous and could allow a path for current to leak if the moist, conductive concrete bridged the dirt on the battery's top, leading to a slow discharge. Today's automotive batteries feature durable, non-conductive polypropylene casings that effectively prevent this type of discharge. The real danger to a battery's charge is not the surface it sits on, but time and temperature.

The primary reason a stored battery dies is due to a phenomenon called parasitic drain. Even when disconnected, batteries naturally self-discharge over time. Furthermore, extreme temperatures, especially cold, significantly accelerate this discharge rate by slowing the chemical reactions inside the battery. A concrete floor in an unheated garage can become very cold, which is the actual culprit behind a dead battery, not the concrete itself.

For long-term storage, the correct procedure is what matters most:

• Clean the Top: Always wipe the battery clean of any dirt or moisture to prevent any potential surface current leakage.
• Disconnect the Terminals: Remove the battery from the vehicle or at least disconnect the negative terminal.
• Use a Battery Maintainer: The best practice is to connect the battery to a battery maintainer or smart charger. This device provides a tiny, intermittent charge to counteract self-discharge, keeping the battery at an optimal voltage indefinitely.

Battery Type	Casing Material	Susceptibility to Concrete Discharge?	Primary Discharge Cause
Old Hard Rubber (Pre-1960s)	Porous Rubber	Yes, if top was dirty/damp	Surface leakage through casing
Modern SLI (Flooded)	Polypropylene	No	Self-discharge & temperature
AGM (Absorbent Glass Mat)	Polypropylene	No	Very low self-discharge
Gel Cell	Polypropylene	No	Very low self-discharge

So, while it's a good habit to place a battery on a wooden block or shelf for organization and to keep it away from dampness, the concrete floor itself is not the enemy. Your focus should be on proper maintenance and temperature control.

[Barbara]

My dad, a mechanic for 40 years, always yelled about this. It was a real thing with the old batteries he started with. Their cases could crack and leak, and a dirty, wet battery on concrete would definitely drain. But he'll also tell you that hasn't been true since probably before I was born. Today's plastic cases fix that problem. I still don't put them on the bare floor, but that's more about keeping them clean and away from knocking them over than anything else. Old habits die hard.

[OKayden]

It’s an outdated worry. Think of it like an old wives' tale for cars. The science behind it made some sense generations ago with different technology. The real issue is that garage floors get cold. A cold battery discharges much faster than a warm one. So, if you leave a battery sitting on that cold concrete for months, it will die. But it’s the temperature, not the material, that’s killing it. A wood shelf just keeps it a bit more insulated.