Vehicle Tips with Jackson Brown Auto & Marine - Batteries, switches and charging systems

Marine batteries need to have a stronger internal construction than automotive batteries due to the extra stress and knocks they take. There are a number of battery designs on the market these days such as traditional lead acid, calcium enhanced, AGM and GEL. The latter two have a higher capacity for the same or smaller physical size and do not self-discharge as quickly but are more expensive.

Battery switches and dual batteries

There are four common types of battery switches in use. The age of the motor, charging system output and amount of batteries will determine the switch set-up to use. They are:

• single on/off switch
• 4 position switch (battery 1, battery 2, both and off positions)
• Three switch set up, one switch for the start battery, one switch for the house battery and one switch for emergency parallel.
• Three switch set up with automatic VSR (voltage sensing relay).

Reasons for a battery switch

Disconnecting the battery from the engine and electronics will stop it going flat quickly while not in use as the engine and electronics all draw current even when turned off. The more electronic devices you have on board the more current draw will be present.

Dual battery selection. If you have extra electronics such as an anchor winch, sounder, GPS, VHF, bilge pump, bait tanks pump, wash down pump and stereo on your boat it is highly recommended to have a dual battery set up on board, then if one battery discharges quickly while at rest, there is still enough power to start the engine once you are ready to move or go home. 

Running the batteries always connected defeats the purpose of having two batteries. Always keep them isolated from each other because the good battery will discharge into the bad battery giving you two half or worse charged batteries. 

Charging systems

The charging systems on many outboards are only capable of charging one battery at a time. With a 4 position battery switch (battery 1, battery 2, both on and off positions) it is recommended to go out on one battery and come home on the other to ensure both get charged. Do not run the boat with the switch in the ‘both’ position (unless there is an emergency) as the charging system will not be able to cope and will not charge either properly. Never change your battery switch position with the engine running as you run the risk of destroying the alternator.

Automotive battery switches are different from marine. Always use a marine rated switch. 

If having to replace your jet ski or boat battery every year it may be a good idea to invest in an electronic ‘plug and forget’ battery charger to maintain it as needed for an infinite amount of time. They cost less than a large marine battery and will keep your batteries in perfect condition all year round. We have these chargers in stock and can advise you on your battery and maintenance needs.

Battery charging and selection

A standard battery charger will not charge a calcium enhanced battery properly as this needs to be charged at a higher voltage. You will need a calcium charger to charge calcium batteries properly. 

When purchasing or charging a marine (or automotive) battery be aware that you will need to match the battery technology to the charging system, e.g. if you have an old outboard with an unregulated charging system you will need to run a standard lead acid battery with vent caps to allow the gas produced to escape and you will need to top up the battery water level regularly. Newer outboards have a voltage regulated system and can supply more amps so can charge larger batteries quickly and can charge calcium batteries.

For questions, comments or queries about batteries, switches or charging systems  please drop in to Jackson Brown Automotive and Marine, 194 Molesworth Drive, Mangawhai or call us on 09 431 4814.