What Caused My Sealed Batteries to Melt?

Thermal Runaway

• Thermal runaway is a condition where an increase in the battery's temperature changes conditions inside such that the temperature continues to increase. If not stopped, this can lead to battery meltdown. Thermal runaway often starts when the valves on a VRLA become blocked. It may also occur if the battery is operated in very hot locations, such that the valves can't provide enough cooling power. Overcharging your sealed lead-acid battery for a long time could also induce thermal runaway and meltdown.

Conductivity Problems

• If the battery connection at the terminal gets too hot because of a dirty contact, loose connection, or corroded surface, the grease around the terminal can melt. This leads to a voltage drop that can reduce the battery's operating life and damage the terminals. Extreme cases can even melt the terminal and cause the battery cover to catch on fire.

Tool Mishandling

• Even small batteries can discharge large amounts of energy if you accidentally short circuit them with an uncoated tool. Plain metal tools that touch both terminals can create a electric path that damages small batteries. In larger batteries, the short circuit can heat the tool up in just a few seconds and potentially melt the terminal. In extreme cases, the battery may explode or catch fire.

Prevention/Solution

• Keep VRLA batteries away from very hot environments, and charge them using a constant voltage system. Periodically test the battery using a voltage meter. Inspect the terminals and connections regularly; if they appear dirty or loose, correct the problem before it causes the battery to heat up. If the battery ever appears swollen or becomes too hot to touch with a bare hand, discontinue use immediately to avoid a meltdown.