Most often, when you encounter a battery that’s past its prime, the warning sign is that it gets really, really hot while charging. Batteries and battery chargers normally heat up while charging—I’ve handled a bunch from tons of manufacturers over the years—but they should be warm, not scorching.

Swelling is a surefire sign that your ebike battery is a goner. Any bulging in the case means that the internal components have degraded to the point that the battery is no longer safe to use or charge.

Leaking is an obvious one. I’d hope that if you saw your battery weeping liquid, whether or not you see a crack, you’d know that something isn’t kosher. This is likelier if you’ve subjected your battery to abuse, such as tossing it roughly into the corner of the garage or having accidentally dropped it one too many times.

You may not notice a crack, but if you smell a putrid odor coming from the battery, it’s another sign that the battery inside is leaking. Quit using it immediately.

How to Tell if Your Ebike Battery Is Bad: A Guide

If your battery exhibits any of these signs, even if it’s just one, you should replace it. As in right now. Don’t use it until you replace it, and don’t charge it again. Make sure it’s unplugged, and keep it unplugged.

Using a damaged battery risks starting an electrical fire, and the last thing you want to do is burn down the building. Don’t toss the old battery in the garage, though. Recycle that baby. You can find a local drop-off site near you.

Yes, I know it’s a bit of a hassle to take it somewhere special, but if you toss that battery in the trash and it ends up in a landfill, its ghost will come back to haunt you. That’s just science, plain and true.