A guide to ensuring longer life and trouble-free, reliable service from marine batteries

Contrary to common belief, it is not the cold of winter that can harm fully charged batteries, it is the number of extra demands we place on them.

The creature comforts we expect in our cars, such as heater/demister and wipers on those chilly winter mornings, can really shorten a battery’s life. Ensuring that batteries are kept fully charged is a vital step in your winterisation program, no matter what type of batteries you use.

Despite the many types of battery currently available to boat owners, they all need to be kept fully charged.

It helps to consider that, as a battery discharges, the sulphur in its acid migrates onto the plates, where it will harden if left there. This is the biggest killer of boat batteries, because once the sulphur forms hardened crystals on the plates no amount of charging or proprietary additives will restore the battery to full health.

All lead acid batteries self-discharge as this chemical action takes place, whether or not you’ve left it on a concrete floor and dependent of type, this can occur as quickly as a factor of 1% per day. So, a standard “antimonial-lead” battery should be checked for its state of charge once each month that it is left in storage.

The best way of checking the state of charge of a “wet acid” battery is by testing the specific gravity of the acid. As previously stated, the sulphur in the acid migrates to the plates as the battery dis-charges, which lowers its specific gravity. It is easy to test for this using a hydrometer. Many “maintenance free” wet acid batteries are equipped with a built in “magic-eye” hydrometer for this exact purpose.

Although a simple voltage test on a stored battery can give a quick indication of charge status, this practice could be fraught with danger. If used on a battery that is being charged, a phenomenon called a “surface charge” will quickly build up a voltage reading that would indicate a charged battery, long before the chemistry that makes the battery work has taken place.

An all too common misconception is that based on the relationship between voltage and state of charge, one that can have serious consequences for the life of your battery.

Just like most humans, batteries don’t like to work hard for long periods and doing so will wear them out more quickly than taking a more leisurely approach. This is especially important when dealing with batteries that provide power for extended or cyclic loads, like house batteries running lighting and refrigeration, or subjected to high-drain loads like powering electric winches.

According to the people at SuperCharge Batteries, a battery had reached 100% “depth of discharge” (it’s maximum discharge for usable life) at 1.75 volts per cell, or 10.5 volts for a 12 volt battery.

However, subjecting a deep cycle battery to this level of discharge through cyclic load/recharge usage will reduce the number of cycles in the battery’s useful life by as much as 70% over that of the same battery discharged to 50% “depth of discharge” or 11.6 volts.

This would be even worse if the battery was not fully re-charged. By the way, a fully charged battery will indicate around 12.8 volts at rest.

For peace of mind, boat owners should ensure that they install the correct combination of starting and deep-cycle batteries and that these are wired with suitable isolation and charge circuits by marine electricians.

At all times, batteries should be kept clean and securely mounted, with clean, corrosion free terminals. Their state of charge should be tested regularly, always with a hydrometer and re-charging done when required.

SuperCharge Batteries, a member of the Ramcar group that boasts more than ninety five years of manufacturing batteries for a wide range of applications, is based in Regency Park and has outlets throughout the State.

Today, SuperCharge Batteries offers a range of high quality models for marine, truck, automotive, motorcycle, industrial applications, deep cycle, dual cycle and starting, as well as chargers, testers and accessories.

For further information, contact SuperCharge Batteries on 8346 9112 or go to www.supercharge.com.au.