Add Second Battery

How to add a second Battery?

by Conrad & Judy Kreuter

Did you ever try to start your motor after a great day of fishing only to find a dead battery? You probably have often thought about adding a second battery and questioned whether it was really needed.

A second battery provides an extra margin safety when used properly. Your engine automatically recharges the battery when it is running. If you have two battery system, the engine will only charge the battery that has been selected by the battery switch. By using a battery switch you can alternate the use of each battery so that you can always count on having two fully charged batteries.

A battery switch has four positions; battery one, battery two, both batteries, and off. The proper way to use a dual battery system is to alternate the use of battery one and two. When using the “both” position the batteries are connected together in parallel which give you twice as much starting current. There should be no reason to use the both position if you are alternating the use of battery one and two. The battery switch should be left in the off position when leaving the boat.

To add a dual battery system to your boat you will need the following parts: a marine starting battery, battery switch, one length of black battery cable, two lengths of red battery cable, battery box or tray, cable clamps and miscellaneous screws, nuts and bolts.

Unless a second battery will throw the boat out of balance, try to locate the second battery close to the original so that the wires can be kept as short as possible. Allow enough room to install the battery switch and battery box or tray close to the same location as the first battery. Make sure the battery switch is in an accessible place so that it is easy to operate.

Connect the new black wire between the negative terminals of each battery. You can leave the existing ground wires attached to the original battery. Remove the positive (red) wires from the first battery and connect them to the common terminal on the battery switch. Add one new red wire to each battery positive terminal, Connect the other end of one of the new red wires to terminal 1 and the end of the other to terminal 2 of the battery switch. Arrange the wires neatly around the batteries and to the battery switch. Use cable clamps to secure the wires to the bulkheads. Make sure the wire from the automatic float switch is connected directly to one of the battery positive terminals. This is important since you will turn the battery switch off when leaving the boat and you do not want to turn off the automatic feature of the bilge pump.

Your local dealer can supply all the necessary parts and expert advise to help in adding a second battery to your boat.