What is a battery?

A battery is a device for storing electrical energy in a chemical form, and then releasing it as direct current in a controlled way. All types of batteries contain a positive and a negative electrode immersed in an electrolyte, the whole assembly being within a container. All batteries are a lead-acid battery, which means that they have positive and negative electrodes made of lead compounds in a dilute sulphuric acid electrolyte. Lead-acid batteries are secondary batteries, which mean that they can be recharged after they have been discharged. Primary batteries can be discharged only once and then have to be thrown away.

How does a battery work?

The positive electrode is made of lead dioxide and the negative electrode is made of porous lead. When an electrical load is connected across the battery, a current flows through the electrolyte in the battery and through the external load. This causes the battery to discharge, which results in the chemical composition of both the electrodes changing to lead sulphate. A battery can be charged by putting a current through the battery from an outside source of electricity such as an alternator, dynamo or charging unit. This converts the lead sulphate back to the original materials of lead dioxide and porous lead. As the battery becomes charged, the electricity begins to decompose the water in the electrolyte into its constituent elements of hydrogen and oxygen, which are released as gas. This is why a battery gases when it is charged.

What is a battery made of?

As the positive and negative electrodes are made of weak materials, they need a mechanical support which is provided by a grid made from a lead alloy; lead on its own would be too soft. In addition to providing a support for the electrodes (the active material), the grid also conducts electricity from the electrodes to the outside load

The electrodes are initially made from a mixture of lead oxide and lead sulphate, and this is converted into lead dioxide in the positive plate and porous lead in the negative plate when the battery is initially charged.

The negative electrode also contains small amounts of additives to give the battery a good discharge performance at low temperatures to improve starting. The combination of grid and electrode is normally called a plate.

The electrolyte is dilute sulphuric acid. This acts as a conductor to transport electrical ions between the positive and negative plates when the battery is being charged or discharged.

The acid also takes part in the discharge as the sulphate ions react chemically at the electrodes to produce lead sulphate.

The separator is an insulator placed between the positive and negative plates to prevent them shorting together.
The separator needs to be microporous with very small holes to allow the ions to flow through the separator from one plate to another. It also needs to be able to resist the high temperatures and strongly acidic oxidising conditions that occur in a battery.

Most modern separators are made of microporous polyethylene, which has suitable properties to meet the demanding conditions within the battery.

Container and Lid
These are normally made of polypropylene, which is a light but strong plastic. Unlike some plastics, it does not become brittle when it is cold, and so can resist knocks during handling. It is not attacked by acid and it can also withstand the fluids (petrol, diesel, brake-fluid, antifreeze) normally found on a vehicle.

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 Europower Battery Centre for advice.

What is the difference between a starting battery, a deep cycle battery and a dual-purpose battery?
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 is it unable to start your car if you accidentally leave the lights on for more than a couple of times.

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.

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 of engine starting but starting batteries should not be used for deep cycle applications.

What is an AGM battery?
This is a totally sealed battery giving high starting performance and deep cycling capability. It is absolutely maintenance free and leak-proof and can therefore be placed in a variety of positions.

AGM batteries absorb the battery acid in the glass fibres and thus binds it in. Since the electrolyte (acid) is contained in the glass mats, it cannot spill, even if the battery is broken. This also means that AGM batteries are non-hazardous. In addition, since there is no liquid to freeze and expand, they are practically immune from freezing damage. The plates in AGM’s are tightly packed and rigidly mounted, and will withstand shock and vibration better than any standard battery.

The AGM battery has an extremely low internal electrical resistance. This, combined with faster acid migration, allows the AGM batteries to deliver and absorb higher rates of amperage than other sealed batteries during discharging and charging.

Nearly all AGM batteries are “recombinant”. This means that the oxygen and hydrogen recombine inside the battery. These use gas phase transfer of oxygen to the negative plates to recombine them back into water while charging and prevent the loss of water through electrolysis. The recombining is typically 99+% efficient, so almost no water is lost.

The charging voltages are the same as for any standard battery; therefore there is no need for any special adjustments or problems with incompatible chargers or charge controls. And, since the internal resistance is extremely low, there is almost no heating of the battery even under heavy charge and discharge currents.

AGM’s have a very low self-discharge – from 1% to 3% per month is usual. This means that they can sit in storage for much longer periods without charging than standard batteries.

What are the advantages and disadvantages of gel, AGM and flooded lead acid deep cycle?
Generally, gel and AGM batteries have about 20% less capacity, cost about twice as much and have a shorter life cycle 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 deep cycling applications whereas AGM are more for light cycling and engine-starting applications.

What is better – a 24 volt or 48 volt system?
Higher-voltage systems tend to be more efficient and put a lower load on the batteries. Factors other than the battery enter into the system’s overall efficiency.

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 indicates 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 sufficient to let the voltage stabilise.

When do I need to perform an equalisation charge?
Equalising should be performed when a battery is first purchased (called a freshening charge) and on a regular basis as needed. This will vary depending on your application. You will need to monitor your battery voltage and specific gravity to determine when equalisation is needed. Reduced performance can also be an indicator that equalising is necessary.

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.

Do batteries self-discharge when not in use?
All batteries will self-discharge regardless of their chemistry. The rage of self-discharge depends on the type of battery, the age of the battery and the storage temperature the batteries are exposed to.

What type of charger should I purchase?
An automatic charger offers the greatest convenience. Just plug the battery into the charger and the charger does the rest. Manual chargers, although equally effective at charging batteries, require a greater level of attention. Generally speaking, automatic chargers are priced higher than manual chargers.

When should I water my batteries?
Water is lost during charging. Therefore, the best time to water your batteries is always at the end of the charge cycle. However, if the electrolyte level is extremely low of the plates are exposed to air, add some water to cover the plates before starting the charge cycle. It is best to check your new batteries regularly as this will give you a good feel for how often your application will require battery watering.

What is the proper electrolyte level?

Liquid levels should be 1/8 inch below the bottom of the vent well (the plastic tube that extends into the battery). The electrolyte level should not drop below the top of the plates.

Do you ever add acid to a battery?

Under normal operating conditions, you never need to add acid. Only distilled, deionised or approved water should be added to achieve the recommended levels mentioned above. Once filled, a battery should only need periodic water addition.

Can a battery freeze?

The only way a battery can freeze if it is left in a state of partial or complete discharge. As the state of charge in the battery decreased, the electrolyte becomes more like water and the freezing temperature increases.

Can I reduce my maintenance by not gassing my batteries?

You will reduce the frequency of watering but will cause a condition known as stratification where the specific gravity of the electrolyte is light at the top of the battery and heavy at the bottom. This condition results in poor performance and reduced battery lift.

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.

Are lead-acid batteries recyclable?

Lead acid batteries are 100% recyclable. Lead is the most recycled metal in the world today. The plastic containers and covers of old batteries are neutralised, reground and used in the manufacture of new battery cases. The electrolyte can be processed for recycled wastewater uses.