Rolls AGM batteries are Deep Cycle VRLA batteries with high reserve capacity, long cycle life and low internal resistance, while achieving superior cranking performance. This allows you to choose AGM batteries for engine start, bow-thrusters and service loads. A key benefit is that you can use a single modern multiple-outlet charger like the Cristec CPS3 range, set to AGM battery charge programme to charge all the batteries properly. In the long term, that means longer life and better performance from the batteries and lower cost to you. It doesn't end there - VRLA batteries are maintenance free and do not vent gas (or leak liquid acid) in normal operation. So, you don't have to install vents, you can stack the batteries as there is no vent/filler to access, no need to use battery boxes to catch acid splashes and you never need to buy and store de-ionised water for topping up with.