Battery Chargers for Lead-Acid Batteries
While people may throw about terms like deep-cycle, flooded, calcium and gel, they all refer to the basic lead-acid battery technology that has been in automotive use for over a hundred years. All these batteries use primarily lead electrodes and a sulphuric acid electrolyte. While they are heavy, they do not have a memory effect, which makes a 12V lead-acid battery a perfect choice for heavy duty applications like starting your car.
How to Charge a Battery
Charging a lead-acid battery is a little more involved than just hooking them up to a power point so they can tap into the mains. A wrongly charged 12V battery can end up never charging at all, or it can overcharge to the point where the electrolyte boils and the battery explodes. A good 12V lead-acid battery charger keeps that from happening. A proper lead-acid charger operates in three stages:
- Constant Current: This provides 70% of the charge, feeding the battery at a constant current and voltage.
- Topping Charge: The topping charge gets your battery most of the rest of the way; it maintains the same voltage but lowers the current to avoid saturation.
- Float Charge: This drops the voltage providing just enough to prevent self-discharge.
Undercharged batteries work, but without the topping charge you get a build-up on the electrodes that permanently reduces the battery's ability to hold a charge.
Difference Between Starter and Deep Cycle
Most car and truck batteries are what's known as a starter battery. These batteries use thin electrodes with a high surface area so that they can provide a quick burst of power to start your car. Deep cycle batteries are for backup power supplies and solar installations or caravans. They have thicker electrodes and cannot produce the same burst of power. Deep cycle batteries are best for constant use at a lower current draw. Always make sure your charger is set for the right type of battery, and when possible use an automatic charger that will shift between the different charging regimes as necessary, basing it on the battery you are charging.
Types of Lead-Acid Batteries
There are two basic types of lead-acid batteries: flooded and AGM. Flooded batteries use a liquid electrolyte and store and function upright. Most are sealed, while a few are open and require that you top them up with distilled water when the levels get low. EFB refers to an Enhanced Flooded Battery, which charges and discharges faster for cars with start-stop technology. AGM refers to Absorbed Glass Mat and has its electrolyte in suspension. These batteries can mount in different orientations. Different battery designs require different charging programmes so it's important to know what you have before hooking it up to the charger.