Understanding Wet and Dry Cell Car Batteries: Types and Mechanisms

When it comes to car batteries, the vast majority are 'wet cells', with flooded lead acid batteries being the most common. Even AGM (Absorbent Glass Mat) batteries, like the well-known Optima brand, fall into this category, despite having the acid absorbed into a fiberglass mat, which provides containment. These types of batteries are standard in most, if not all, IC (internal combustion engine) vehicles. While there are no known dry cell car batteries, it's worth noting that such batteries, if they exist, would likely be quite rare.

Why Wet Cells Cater to Cost and Maintenance

In most cases, flooded wet cells are more affordable, often being three times less expensive. Additionally, the electrolyte level in these batteries can be checked and, should the battery become overheated or overcharged, it can be topped up with distilled water. This is not a feature of dry cells, which rely on an internal reservoir for electrolyte management.

Clarifying the Misnomer: Are Dry Cells Really Dry?

Contrary to popular belief, the term 'dry cell' is a misnomer. Dry cells do not use dry electrolytes, but rather consist of a full flooded wet-cell with an added reservoir for electrolyte. Moreover, they often contain more liquid electrolyte than the simple design they're re-named from. A so-called dry cell is essentially a fully flooded wet cell with an additional reservoir for electrolyte and a recirculation system.

These batteries feature a fluid reservoir mounted higher than the cell-pack, which uses the natural convection of heated electrolyte and gas bubbles to pump the electrolyte/gas mixture from the reservoir to the cell-pack, ensuring a continuous supply of fresh electrolyte. The design allows for the hydrogen gas (BG) or HHO to exit the system, while the de-gassed electrolyte re-enters the bottom of the electrolyzer. Dry-cells can be designed with parallel-plate or series-plate configurations, the same as traditional wet-cells. In essence, any electrolyzer can be converted to a dry-cell by adding a reservoir and recirculation hoses.

The Original and the Terminology: Wet and Dry Cells

The term 'wet cell' refers to the earliest type of rechargeable battery, commonly found in aviation, electric utilities, energy storage, and cellphone towers. These batteries contain a liquid electrolyte, often sulfuric acid, a corrosive substance that can damage materials it comes into contact with. The originator of this terminology used 'dry cell' to differentiate recirculating-electrolyte designs from the original, simpler designs that were named 'wet cells.'

Although dry-cells are termed 'dry,' they actually utilize a larger volume of liquid electrolyte than wet cells. Dry-cells are, in fact, an electrolyte-circulating electrolyzer system. Thus, nearly any electrolyzer can be converted to a dry-cell by adding a reservoir tank and recirculation hoses. However, just because a battery is a dry-cell doesn't make it more efficient; in most cases, the efficiency is comparable, or even lower, than a wet-cell battery.

Conclusion

While dry cells are a misnomer, understanding the distinctions between wet and dry cells can help drivers make informed decisions about their vehicle's power source. Wet cells are cheaper, maintainable with distilled water replenishment, and constitute the majority of car batteries available today. Dry cells, while potentially more efficient, are rarely used in vehicles due to their specialized design and the complexity of their management systems.

Consumers should carefully consider their needs and the specific requirements of their vehicles when choosing a battery. Whether you're looking for cost-effective maintenance or seeking the latest in battery technology, understanding the differences between wet and dry cells can guide you towards the best choice for your car.