Marine Battery Maintenance




Checking your battery regularly can help to maximise battery life. A routine inspection at least once a month is recommended to maintain optimum performance.

Always keep your battery fully charged

deep-cycle-battery-(1).jpgYour Marine battery prefers to be kept fully charged when not in use, at a voltage of 12.5v or above. If a battery is left in a partially discharged or flat state for extended periods of time, irreversable internal damage will gradually begin to occur, greatly reducing the overall service life you will get out of it.

  • Check your Marine battery voltage with a voltmeter
  • Always ensure the voltage remains above 12.5 volts
  • Always recharge the battery fully after you have returned from a trip
  • Re-check your battery voltage at least once a month

Keep the battery and connections in good condition

Ensure the top of your Marine battery remains clean, dry, free of dirt and grime. A dirty battery may begin to lose it's charge faster, as an electrical current may travel across the grime on top of the battery casing. Inspect the battery case for obvious signs of physical damage or warpage. This usually indicates the battery has been overheated or has been overcharged.

If you have a maintainable battery (with removable caps on top) it is important to check if the battery has sufficient electrolyte (water) inside to cover the battery plates. If topping up is required, use distilled or demineralised water only. 

  • Inspect the battery perodically and ensure that the top surface remains clean
  • Inspect the battery case for any signs of damage or warping
  • Inspect the terminals, screws, clamps and cables for damage or loose connections
  • Check electrolyte level of maintainable batteries, and top up if required
  • Optional: Apply a thin coating of high temperature grease to terminals to reduce corrosion build up



After use, your Marine battery should be recharged using a proper multi-stage battery charger. Lead acid batteries should be charged in 3 stages; constant current (boost), constant voltage (absorption) and float charge.

Choosing the right battery charger

There are many different chargers on the market with varying amp ratings - so make sure you use the following steps to determinte which battery charger is right for your battery.

  • Make sure the charger voltage matches the battery - 6-volt or 12-volt
  • Determine the ampere hour (Ah) rating of your battery (this is listed on top)
  • Divide the Ah rating by 10 to determine the ideal charger amp rating (eg. 80Ah / 10 = 8 amps)
    • For AGM or GEL batteries, divide by 5 instead (eg. 80Ah / 5 = 16 amps)
  • Choose a battery charger with an amp rating as close as possible to this figure
  • For this example, a 12-volt battery charger with an 8 amp setting would be suitable

Using a battery charger safely

Before attempting to charge a battery with an external battery charger, it is important to be aware of the safety precautions when charging batteries and follow the instructions outlined by the charger manufacturer.

  • Turn the charger off before attaching, rocking or removing the terminal clamps
  • Keep open flames and sparks away from the battery
  • Do not remove vent caps (maintainable batteries only)
  • Charge in well ventilated area
  • Follow the battery charger manufacturer’s instructions to avoid overheating

Dangerous explosive gases are generated during the charging process that can be ignited by a variety of sources including, sparks, naked flames and static electricity. It is highly recommended to wear PPE (Personal Protection Equipment) including safety glasses, chemical resistant gloves and overalls.  



Before removing or installing a battery ensure that all electrical equipment within the vehicle is turned off, including the ignition system, air-conditioning, lights and radio.

Removal of old battery

Before removing the old or existing battery from your vehicle, take note of the Positive(+) and Negative(-) terminals on the battery, and ensure that your replacement battery is of the same type and terminal layout.
  • Always loosen and remove the Negative(-) terminal first, using an appropriate size spanner
  • Remove the Positive(+) terminal and ensure both terminals are pushed away from the battery
  • Undo the battery hold down clamp
  • Safely remove the battery using the built-in handle

New battery installation

Ensure your vehicle's ignition system is "off" before installing your new Marine battery.
  • Ensure check the battery size and terminal layout to ensure it matches your existing/old battery
  • Inspect the battery tray area for corrosion, and clean with water and baking soda if necessary
  • Place the new battery in the tray, ensuring it sits level
  • Double check the terminal posts to ensure the Positive(+) and Negative(-) terminals are on the correct sides
  • Install the battery hold down clamp, tightening until the battery does not move
  • Connect and tighten the Positive(+) terminal, ensuring it is pushed all the way down onto the battery post
  • Connect the Negative(-) terminal in the same way
  • If your battery setup has rubber caps to protect the terminals, slide these back into place

If in doubt, please contact your battery retailer for assistance or to obtain the correct information. Any mistakes made during installation - in particular connecting the terminals to the opposite battery posts - could potentially cause damage to your Marine battery and also your vehicle's electrical system.



Below is a list of frequently asked questions:

Q. Why has my battery gone flat?

There can be many reasons why a battery has gone flat, but it is usually due to:

  • It was left partially or fully discharged for long periods of time - This can cause permanent damage to the battery and drastically reduce the service life you could expect from it.
  • Human Error - Accidentally leaving on lights or accessories which have flattened the battery.
  • Parasitic drain - Components in the vehicle which draw standby power and gradually wear a battery down over time.
  • It's an old battery - Old batteries are simply not as good at holding their charge. Lead-acid batteries last 42 months on average, so if a battery is beyond this age you're on borrowed time.

If you've recently experienced a flat battery, it is important to have your battery retailer investigate whether any problems exist with the vehicle's charging system before a new battery is fitted.

Q. Will going for a drive recharge a flat battery?

Simply going for a drive will not provide enough charge to recharge a flat battery. Vehicle charging systems are designed to provide a 'surface charge' which is sufficient to maintain a healthy battery, but nowhere near enough to bring a flat battery back from the dead. The only way to recharge a flat battery is to use a proper multi-stage battery charger, with an amp rating high enough to restore the battery to peak performance.

Q. Why do batteries go flat over time?

Almost all batteries have a natural tendency to go flat over time, especially when they're not in use. If you've got an old mobile phone stored in a draw at home, you'll notice it'll probably be flat the next time to try to turn it on - and it's the same story with your Marine battery. For batteries that are rarely used, it's important to test and charge them regularly to prevent them from self-discharging and going flat.

Q. Why did my battery only last a few years?

Lead-acid batteries last 42 months on average - however this figure may be reduced or extended depending on a number of factors, including:

  • Whether the battery has been installed correctly.
  • If the battery chosen is suitable for the application.
  • The climate in which the vehicle is driven.
  • The voltage which the battery is usually kept at.
  • Whether the vehicle has high or low parasitic drain when not in use.

Q. Can I use tap water to top up a maintainable battery?

No. While tap water might be easy to source, adding it to your maintainable battery is not a great idea unless you are in an emergency situation. Tap water contains minerals which will accelerate corrosion - reducing the performance and life of the battery. Always use distilled or demineralised water to top up maintainable batteries.

Q. Does my battery really need a hold down bracket?

Yes! Unsecured batteries can be damaged by impact or vibration damage as they move around, and you also run the risk of the battery 'shorting out' if the battery posts or terminals make contact with any metal objects - potentially starting a fire or causing the battery to explode. Unsecured batteries also tend to have a reduced lifespan - due to increased vibration damage.


Battery Health & Safety

Battery Acid

Battery acid can cause burns. Suitable hand, eye and face protection and protective clothing must be worn.

First Aid

For advice, contact the poisons information centre (phone 13 11 26 in Australia) or a doctor immediately. If in eyes, hold eyelids apart and flush the eye continuously with running water. Continue flushing until advised to stop by poisons information centre or doctor, or at least 15 minutes. If skin or hair contact occurs, remove contaminated clothing and flush skin or hair with running water.

Acid Spill Response

Bund and neutralise spills with soda ash or other suitable alkali. Dispose of residue as chemical waste or as per local requirements.

If Electrolyte is Swallowed

Do NOT induce vomiting – give a glass of water. Seek immediate medical assistance.

Exploding Battery

Batteries generate explosive gases during vehicle operation and when charged separately. Flames, sparks, burning cigarettes or other ignition sources must be kept away at all times. Exercise caution when working with metallic tools or conductors to prevent short circuits and sparks.

Always Wear Eye Protection

When charging batteries, work in a well-ventilated area - never in a closed room. Always turn battery charger or ignition off before disconnecting a battery.