Not surprisingly, batteries are made to be ‘job specific’.
Deep Cycle batteries used for your motorhome house/leisure battery are constructed very differently to batteries used to start vehicles.
For example, a starting battery has to provide a high current surge to start an engine, but once that has been achieved the vehicle’s alternator immediately replenishes the power it provided. In contrast, a deep cycle battery must provide a steady flow of current over a long period and sometimes doesn't get recharged again until the voltage level has significantly dropped. Although ALL the batteries you'll find here belong to the deep cycle class, there are a few different styles to be aware of. Lead/acid batteries are generally the most common in the caravan industry. They should be installed in a vented area and require occasional maintenance in the form of checking the water levels. Absorbent Glass Mat (AGM) batteries are completely sealed, maintenance free and don't require ventilation. They are a little more versatile and can generally achieve more cycles - meaning a longer working life. Gel batteries are also completely sealed and won't leak corrosive acid if they are severely cracked during an accident. Unfortunately, their maximum charging voltage is a little lower than more common battery types which means you need a specialised charger with a ‘gel’ setting. You probably won't be able to parallel charge a gel battery directly from your alternator either as it uses a higher charging voltage.