This can sometimes be difficult if using a battery to run electronic accessories or if you re using more than one battery at once. A good engine will generate plenty of power for batteries not only at full throttle, but at mid throttle and trolling speeds outboards, for example, feature High Output Charging Systems. The system also separates the starting battery from the accessorybattery when the engine is off, ensuring that the starting battery retains enough power to get the engine going again. If your charging system works fine, yet the battery remains undercharged, test the acid strength with a hydrometer. If, like most boaters, you do not have a hydrometer, then have a marine dealer perform the test for you.
Proper storage can also increase the life of a battery.
Whenever yourbattery sits idle for more than a month, remove it from the boat and place it in a warm dry area. If your garage has a concrete floor, placethe battery on a piece of wood to keep it insulated from the cold ground. Just like on the water, batteries should remain fully charged while in storage. Theconventional batteries use lead alimony which contains impurities and this lessens the life of the battery. When you recharge that battery you will smell the battery acid as it is being vented.