Deep cycle
Battery designed for repeated deep discharges. Uses: marine, solar, caravans, mobility scooters.
A deep cycle battery is built to withstand discharges down to 50-80% of its nominal capacity and recharge hundreds or thousands of times without significant degradation. The opposite of a starting (SLI) battery, which only tolerates about 5% repeated discharge. Internally they have thicker, more robust plates (less active surface but more material per plate) and reinforced separators. Common technologies are AGM Deep Cycle and GEL. They are measured in usable Ah (not CCA like starting batteries): a 100 Ah deep cycle delivers 5 A for 20 hours. Typical applications: leisure boats (powering services with the engine stopped), caravans and motorhomes (auxiliary habitation battery), off-grid solar systems, electric wheelchairs.
Reference brands: Varta LFD, Optima YellowTop, Trojan, Fullriver DC.