A battery is basically a chemical reaction in a box. In a simplified view, the main components are the positive and negative terminals on the sides called electrodes and a chemical solution between them called electrolyte. When you’re drawing power from a battery you’re creating an electrical circuit and causing a chemical reaction inside the battery whereby charged particles called ions flow from one electrode to the other. This translates into a flow of electrons (negative charged particles) out from the battery’s negative terminal through the circuit to the positive terminal, generating electricity through the wires connected to the battery. When you charge up a battery, electrons flow back to the battery from the positive to negative terminal, creating a chemical reaction once again and restoring charge to the battery.
The types of chemicals making up the electrodes and electrolyte gives us the different types of batteries in common use today. The starter battery in automobiles is a lead acid battery, comprised of lead and lead oxide as the electrodes and sulfuric acid diluted in water as the electrolyte. Everyday consumer rechargebale double AA or triple AAA batteries have either nickel-cadmium (NiCd) or nickel-metal-hydride (NiMH) as electrodes and potassium hydroxide as electrolyte. The battery in your phone, video camera or Yeti-type solar charger is a lithium battery, the name coming from the lithium in the electrodes.
Lead acid batteries are categorized as either cranking or deep cycle. The cranking battery gives a rapid burst of energy, making it ideal as an engine starter battery. The deep cycle battery delivers less immediate energy but is more suitable for long term use, as it can endure more charge and discharge cycles than the cranking battery. In a camper van setting, you would either use a heavy duty lithium battery or a deep cycle lead acid battery to power your electrical devices. For deep cycle batteries, they are sized by group numbers (such as “Group 29”) and the larger the number, the bigger is the battery physically and the more capacity or power will it have.
When shopping for deep cycle batteries (also referred to as marine batteries as they’re commonly used on boats), there are three main classifications to choose from. The first type is the wet cell or flooded battery, named for its liquid electrolyte. The second type is the gel cell, in which the sulfuric acid is mixed with silica to create a stiffer gel-like electrolyte. The third type is known as an AGM battery, short for absorbed glass mat. AGM batteries consist of very fine glass fibres woven into a mat that holds the electrolyte. The gel cell and AGM batteries are more expensive but are more durable, efficient and safer. The gell cells, however, require special battery chargers to maximize performance and prevent premature failure. Check with the manufacturer for specific details.