Everything for Electronics

From the Q&A

With TJ Byers

Battery Quiz


Batteries are divided into two types: dry and wet. For sealed and non-sealed lead-acid batteries, are both considered wet?

— N.S.


In a manner of speaking, all lead-acid batteries are wet. As to how wet is a matter of definition. Most unsealed lead-acid batteries — like those under the hood of your car — are categorized as flooded. That means they have water as their base with a hint of sulfuric acid. If they are tipped sideways, they spill out corrosive liquid water (the newer cap-less batteries to a lesser extent — but still). Gel-cells use a thixotropic gelled electrolyte that behaves more like Silly Putty than water (think the Steve McQueen movie The Blob). Therefore, it can be operated in virtually any position — although upside-down is not recommended. The “liquid” is trapped in the cell by special pressurized sealing vents. The sealing vent is critical to the performance of the gel-cell. The cell must maintain a positive internal pressure. If opened, the cell will quickly evaporate and not perform.

What constitutes a dry cell? A carbon-zinc cell, alkaline “Bunny” battery, lithium watch cell, among others. Anything without a liquid or gel electrolyte. While most dry cells are primary — that is, they can’t be recharged — the ability to recharge doesn’t draw the line between wet and dry because today’s new crop of dry-cell Li-Ion batteries are rechargeable. Dry cell leakage? A topic for another day.