Battery Selection

How do I select the right battery for my application?

Proper battery selection may require the assistance of a knowledgeable battery sales/service technician. Please contact your nearest Positive Batteries here and ask for assistance from one of our friendly staff.

What is the difference between a deep cycle battery, a starting battery, and a dual-purpose battery?

A deep cycle battery has the ability to be deeply discharged and charged many times during its service life. It is designed specifically for powering electrical equipment for long periods of time. An automotive or starting battery is designed for brief bursts of high current and cannot withstand more than a few deep discharges before failure. This is why it is unable to start your car if you accidentally leave the lights on more than a couple of times. For applications where both engine starting and light deep cycling are required, a dual-purpose battery is often used. This type of battery is neither a starting nor a deep cycle battery but rather a compromise between the two so it performs both functions adequately.

Can I use my Deep Cycle battery as a starting battery?

Deep cycle batteries can be used for engine starting but starting batteries should not be used for deep cycle applications. A deep cycle battery may have less cranking amps per kilogram than a starting battery, but in most cases a deep cycle battery is still more than adequate for the purpose of starting an engine.

What are the advantages and disadvantages of gel, AGM, and flooded lead acid deep cycle?

Generally, gel and AGM cost about two times more, and have a shorter cycle life than comparable flooded lead acid batteries. However, Gel and AGM batteries do not need watering, are safer (no acid spilling out), can be placed in a variety of positions, have a slower self-discharge characteristic, and are more efficient in charging and discharging than flooded batteries. Gel batteries are more suitable for heavy deep cycling applications whereas AGM batteries are more for light to medium cycling and engine-starting applications.

Battery Charging

How can a battery’s state of charge be accurately measured?

The state of charge of a lead acid battery is most accurately determined by measuring the specific gravity of the electrolyte. This is done with a hydrometer.

Battery voltage also gives an indication of the level of charge when measured in an open circuit condition. This should be done with a voltmeter. For an accurate voltage reading, the battery should also be allowed to rest for a period of at least 3 hours to let the voltage stabilise.

Does my deep cycle battery develop a memory?

Lead acid batteries do not develop any type of memory. This means that you do not have to deep discharge or completely discharge a battery before recharging it. For optimum life and performance, we generally recommend a discharge of 20 to 50% of the battery’s rated capacity even though the battery is capable of being cycled to 80%.

Do batteries self-discharge when not in use?

All batteries, regardless of their chemistry, self-discharge. The rate of self-discharge depends on the type of battery, the age of the battery, and the storage temperature the batteries are exposed to. As an estimate, batteries self-discharge approximately 4% per month at 27°C.

What size charger should I buy?

A properly sized charger takes into account battery capacity and the time interval between charges. In applications where cycling is infrequent, such as weekend caravan users, or infrequent or seasonal trolling motor usage, a charger with an output current rating between 10 and 13% of the battery’s rated 20-hour capacity will suffice. In applications where battery recharge must be accomplished within 8 to 10 hours, a three stage, automatic charger, rated at 20% of the battery capacity, may be required. Example: A good charging rate for a battery with a 20-hr capacity of 225 amp-hr is about 22 to 29 amps. You can of course go slightly higher or lower depending on what is available on the market.

Battery Maintenance

How can I tell if a battery is bad?

To determine if the battery system is experiencing a problem, fully charge the batteries then shut off the charger and remove all electrical loads. Allow each battery in the system to stand on open-circuit for about one hour. Measure the voltage of each battery. If the battery voltage spread exceeds 15 volts for a 6 volt battery, or .30 volts for a 12 volt battery, a problem is indicated. Battery voltage alone does not confirm a problem. When the voltage spread indicates a problem, confirmation is accomplished by taking electrolyte specific gravity readings using a hydrometer. If the specific gravity readings show a spread greater than .030 (30 points), give the batteries an equalisation.

What is used to clean a battery and neutralise the electrolyte?

A solution of baking soda and water. Use 1 lb of baking soda for every gallon of water.

Battery Recycling

Are lead acid batteries recyclable?

Lead acid batteries are 97% recyclable. Lead is the most recycled metal in the world today. The plastic containers and covers of old batteries are neutralized, reground and used in the manufacture of new battery cases. The electrolyte can be processed for recycled waste water uses. In some cases, the electrolyte is cleaned and reprocessed and sold as battery grade electrolyte. In other instances, the sulfate content is removed as Ammonia Sulfate and used in fertilizers. The separators are often used as a fuel source for the recycling process.

Where do I recycle my junk batteries?

Contact our national collection service on 1300 783 879, book a collection online or drop your used batteries into an Enirgi Power Storage outlet.

Battery Temperature

How does temperature affect the performance of my batteries?

At higher temperatures (above 25°C) battery capacity generally increases, usually at the cost of battery life. Higher temperatures also increase the self-discharge characteristic. Colder temperatures (below 25°C) will lower battery capacity and prolong battery life. Cooler temperatures will slow self-discharge. Therefore, operating batteries at temperatures at or slightly below 25°C will optimize both performance and life.

How do I account for temperature when taking my voltage readings?

Temperature will affect voltage readings. As temperature increases, voltage decreases. Conversely, as temperature decreases, voltage increases.

Is there a maximum temperature for charging my batteries?

When charging lead acid batteries, the temperature should not exceed 45°C. At this point the battery should be taken off charge and allowed to cool before resuming the charge process.

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Battery Maintenance

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Before Getting Started

  • Make sure you know your system voltage, battery compartment size (length, width and height) and your energy needs.
  • Determine whether you want to use a deep-cycle flooded, AGM or Gel battery.

Step One: Determine your battery voltage and how many to use.

1-1 Based on your system voltage, you must first decide which battery is needed and how many to use in order to meet your requirements. For example, you may connect a series of eight 6V batteries, six 8V batteries or four 12V batteries for a 48-volt system. The size of your battery compartment, your performance requirements and costs may limit your options.

1-2 Make sure there is enough space between batteries to allow for minor battery expansion that occurs during use and to allow proper airflow to keep battery temperature down in hot environments.

TIP: Connecting batteries in series does not increase the capacity of the batteries; it simply increases the overall voltage to meet your system requirements. Once your voltage requirements are met, if space allows you can double the batteries in a parallel connection, thereby doubling your battery capacity. See diagrams below.

Series Connect

To increase voltage, connect batteries in series.
This will not increase the system capacity.

Two T-105, 6V Batteries rated at 225AH

Connected in Series
System Voltage: 6V + 6V = 12V
System Capacity = 225AH

To increase voltage, connect batteries in series.

Parallel Connect

To increase capacity, connect batteries in parallel.
This will not increase the system voltage.

Two T-105, 6V Batteries rated at 225AH

Connected in Parallel
System Voltage: 6V
System Capacity = 225AH + 225AH = 450AH

To increase amp-hour capacity, connect batteries in parallel.

Series/ Parallel Connect

To increase both voltage and capacity, connect additional batteries in series and parallel.

Example :
Four T-105, 6V Batteries rated at 225AH

Connected in Series/Parallel
System Voltage: 6V + 6V = 12V
System Capacity = 225AH + 225AH = 450AH

To increase both voltage and amp-hour capacity, connect batteries in series/parallel.

Step Two: Choose your best battery model

2-1 When choosing your battery model, first consider your battery compartment space as this may limit your options. Within your size restrictions you may have several battery options to choose from. For example, you can use a T-605, T-105 or T-125 in the same space, as they are the exact same physical size. The difference between these batteries is the amount of energy they have to offer. 2-2 Next consider your energy needs. If replacing an existing battery, use it as a reference point. If your old battery provided enough energy, it can be replaced with a similar capacity battery. If you need more energy you can size up, or if you need less energy you can size down.

Step Three: Select your best terminal

3-1 Finally determine which terminal option best meets your needs based on the type of cable connections you plan to use. Look for the terminal(s) available for the battery you have selected.

Battery Inspection

There are many tools that may help in properly caring for and maintaining batteries. Below is a list of basic items that Trojan recommends for this task:

Recommended Equipment:

  • Spanner
  • Post Cleaner
  • Distilled Water
  • Baking Soda
  • Voltmeter
  • Vaseline
  • Hydrometer
  • Goggles & Gloves

CAUTION: Always wear protective clothing, gloves and goggles when handling batteries, electrolyte and charging your battery.

Batteries should be carefully inspected on a regular basis in order to detect and correct potential problems before they can do harm. It is a great idea to start this routine when the batteries are first received.

Inspection Guidelines:

1. Examine the outside appearance of the battery.

  • Look for cracks in the container.
  • The top of the battery, posts, and connections should be clean, free of dirt, fluids, and corrosion. If batteries are dirty, refer to the Cleaning section for the proper cleaning procedure.
  • Repair or replace any damaged batteries.

2. Any fluids on or around the battery may be an indication that electrolyte is spilling, leaching, or leaking out.

  • Leaking batteries must be repaired or replaced.

3. Check all battery cables and their connections.

  • Look closely for loose or damaged parts.
  • Battery cables should be intact; broken or frayed cables can be extremely hazardous.
  • Replace any cable that looks suspicious.

4. Tighten all wiring connections to the proper specification (see below). Make certain there is good contact with the terminals.

Proper Torque Values for Connection Hardware

  • Automotive 10Nm
  • Side 10Nm
  • Wingnut 15Nm
  • Stud 20Nm

WARNING: Do not overtighten terminals. Doing so can result in post breakage, post meltdown, or fire.


Battery Charging

Battery Charger Selection

Most deep-cycle applications have some sort of charging system already installed for battery charging (e.g. solar panels, inverter, golf car charger, alternator, etc.). However, there are still systems with deep-cycle batteries where an individual charger must be selected. The following will help in making a proper selection.

There are many types of chargers available today. They are usually rated by their start rate, the rate in amperes that the charger will supply at the beginning of the charge cycle. When selecting a charger, the charge rate should be between 10% and 13% of the battery’s 20-hour AH capacity. For example, a battery with a 20-hour capacity rating of 225 AH will use a charger rated between approximately 23 and 30 amps (for multiple battery charging use the AH rating of the entire bank). Chargers with lower ratings can be used but the charging time will be increased.

Charging Batteries

Charging batteries properly requires administering the right amount of current at the right voltage. Most charging equipment automatically regulates these values. Some chargers allow the user to set these values. Both automatic and manual equipment can present difficulties in charging. Tables 2 & 3 list most of the necessary voltage settings one might need to program a charger. In either case the original instructions for your charging equipment should also be referenced for proper charging. Here is list of helpful items to remember when charging.

  • Become familiar with and follow the instructions issued by the charger manufacturer.
  • Batteries should be charged after each period of use.
  • Lead acid batteries do not develop a memory and need not be fully discharged before recharging.
  • Charge only in well-ventilated area. Keep sparks or flames away from a charging battery.
  • Verify charger voltage settings are correct (Table 2).

Additional VRLA Charging Instructions:

  1. Become familiar with and follow the instructions issued by the charger manufacturer.
  2. Verify charger has necessary VRLA setting.
  3. Set charger to VRLA voltage settings (Table 3).
  4. Do not overcharge VRLA batteries. Overcharging will dry out the electrolyte and damage battery.

Battery Storage

Periods of inactivity can be extremely harmful to lead acid batteries. When placing a battery into storage, follow the recommendations below to insure that the battery remains healthy and ready for use.

NOTE: Storing, charging or operating batteries on concrete is perfectly OK. The most important things to avoid:

  1. Freezing. Avoid locations where freezing temperature is expected. Keeping a battery at a high state of charge will also prevent freezing. Freezing results in irreparable damage to a battery’s plates and container.
  2. Heat. Avoid direct exposure to heat sources, such as radiators or space heaters. Temperatures above 26°C accelerate the battery’s self-discharge characteristics.

Step by step storage procedure:

  1. Completely charge the battery before storing.
  2. Store the battery in a cool, dry location, protected from the elements.
  3. During storage, monitor the specific gravity (flooded) or voltage. Batteries in storage should be given a boost charge when they show a 70% charge or less. See Table 1 in the Testing Section.
  4. Completely charge the battery before re-activating.
  5. For optimum performance, equalize the batteries (flooded) before putting them back into service. Refer to the Equalizing section for this procedure.

WARNING: Never add acid to a battery.

Battery Cleaning

Batteries seem to attract dust, dirt, and grime. Keeping them clean will help one spot trouble signs if they appear and avoid problems associated with grime.

  1. Check that all vent caps are tightly in place.
  2. Clean the battery top with a cloth or brush and a solution of baking soda and water.- When cleaning, do not allow any cleaning solution, or other foreign matter to get inside the battery.
  3. Rinse with water and dry with a clean cloth.
  4. Clean battery terminals and the inside of cable clamps using a post and clamp cleaner.- Clean terminals will have a bright metallic shine.
  5. Reconnect the clamps to the terminals and thinly coat them with petroleum jelly (Vaseline) to prevent corrosion.
  6. Keep the area around batteries clean and dry.