Choosing the Right Battery for the Job

choosing the right battery for the job

This is the third in a series of articles by Redarc Electronics about choosing the right battery for the job, this time we are looking at providing the right charge to the battery. 

In the first article we discussed choosing the right battery for the job and discharge characteristics, in the second article we looked at where on a vehicle a battery will be fitted and environments of operation and now we need to consider how to get the right charge to the battery.

Providing the correct charge to a battery is no different to filling your tank with the correct fuel for your engine. You wouldn’t supply diesel to your petrol engine, that one is obvious. On the finer end of the scale, you would be better off supplying high octane fuel to a high performance engine – to fully realise its potential. And in the past, engines that required leaded fuels would last longer if this fuel or an additive were used.

Batteries respond much the same as your engine when the type of charge provided differs from that which the battery manufacturer suggests. The way the battery has been designed and constructed dictates the requirements for being recharged as well as discharged. 

If the charging profile recommended by the battery manufacturer is adhered to when recharging any battery including Gel, AGM, standard, calcium and lithium, whether it is deep cycle or cranking, the battery will give higher power output and tolerate many more cycles than a battery that has not been charged in this way. 

To identify the charge profile a battery requires, and the characteristics that can be expected from the battery in terms of cold cranking amps, amp hours, and some even to the extent of number of cycles, the battery manufacturers’ data sheet must be referred to. Most reputable battery brands and retailers can provide this information when purchasing a battery for any task.

There are many different applications for batteries, such as standby or backup power, and these usually require a slightly different charging profile to a battery that is in use in a prime mover, heavy rigid or semi-trailer – being used regularly – and so we will concentrate on the latter for this in our application. 

There are two major components to a battery charging profile that need to be considered when selecting the right charging profile for your battery. These are the voltage level to be applied to achieve a full state of charge, and the maximum current limit to be allowed to ensure the battery is not charged too quickly resulting in damage, yet still charging in a timely manner. Other factors such as time and temperature come into play as well, which a high quality multistage battery charger will manage during operation.

The vehicle alternator has been relied on for many years to not only recover the power in the start battery from cranking the engine and providing the vehicle electrical systems, but also recharge auxiliary batteries on the truck or trailer. 

Being that an alternator generally does not put out more than about 14V (or 28V for 24V systems), and most modern alternators even less, the requirement of all batteries to be charged with a higher voltage than this results in them being undercharged from the alternator alone. 

Additionally, the alternator has no ability to limit the current to the battery to the correct level for the specific battery type. Advancements in electronics design by innovative companies such as Redarc has given us the ability to apply the correct voltage and current levels to our batteries in both 240V chargers and In-Vehicle chargers to achieve optimum charging at all times.

choosing the right battery for the job

Multistage charging is different stages of charge that apply a specific voltage and current level to the battery for a set period of time or until the current acceptance of the battery falls to a certain value. For example, a battery that is currently in use, running a fridge for instance, requires three charge stages to safely recharge it to 100% state of charge.

Boost: Full charger current, charger size should be chosen so as not to exceed the batteries maximum allowable charge current, until the batteries maximum charging voltage is reached (also known as constant current stage).

Absorption: The voltage is held at the batteries maximum charge voltage until the current acceptance of the battery falls below the required level to determine that it is full (also known as constant voltage stage).

Float: The battery voltage is held at a safe voltage to maintain it at full for extended periods without overcharging, the load on the battery may be covered by the charger rather than discharging the battery during ongoing charging (such as the fridge running while driving or when solar is available).

This three stage type charging can be found in the Redarc In-Vehicle Battery Charger (BCDC) family and Battery Management Systems (Manager30), with specific battery type settings to suit the required charge voltage of the five major automotive batteries, Lithium, Gel, AGM, Standard Lead Acid, and Calcium content. A range of current output level units are available to suit the battery or battery banks current requirements, from 6 amp to 50 amp (12V), and 20A (24V).

A further two charge stages are provided in the five stage Storage mode in the Redarc Battery Management Systems. A battery that is in use will be charged with the three stage Touring mode, but when not in use for long periods it will benefit from these extra stages.

Equalisation: A higher than maximum charge voltage is applied to flooded cell batteries to ensure equal charge between each of the cells is achieved.

Maintenance: The battery voltage is allowed to fall to its open circuit voltage to monitor for battery faults such as shorted or open circuit cells, and also ensure the battery is not overcharged due to prolonged float charging, float will be resumed when required to overcome the batteries self-discharge.

It is also advisable to use a high quality 240V charger on vehicle cranking batteries periodically (once a month) to extend their life. Charging your start battery to 100% state of charge on a multistage charger such as Redarc’s Smart Battery Chargers will ensure that the start battery is ready to crank whenever you need it, and can even pickup faults in the battery that may cause you an issue down the track.

You can spend hundreds of dollars on high quality batteries, but even the most expensive battery won’t perform or last very long if it is not charged correctly. To ensure you get the expected performance and value for money from your batteries, make sure you refer to the battery manufacturers’ data sheet and visit to select your battery charging solution and make sure you stay in charge.

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