Charging your car battery

charging your car battery
  • Driving your car around the block a few times is not enough to charge your battery these days
  • Avoid a flat battery by using a battery charger
  • The different types of battery charging
  • Battery charging can be a way to increase the longevity and performance of your car battery

These days, driving your car around the block a few times is not enough to charge your battery but a flat battery can be avoided if you have a battery charger.
Short journeys often involve lots of stop/start driving, making components such as your car battery work harder. Eventually, because more current is being drained from the battery than the alternator can put back, your battery will not have enough power to charge the starter motor.  

Modern technologies and advanced electrics mean that you need a certified battery charger to do the job. By using a battery charger, you can:

  • Extend battery life
  • Restore battery performance
  • Minimise the chance of a breakdown

A battery charger is a device that charges a rechargeable battery by forcing an electric current through it.

The charge supplied will vary depending on what kind of battery is being charged. For example, the charge regime used to recharge a calcium (Ca-Ca) car battery is different to the regime required to recharge a deep cycle marine battery or an AGM (Absorbed Glass Mat) battery. There are a number of different types of Lead Acid battery types, and using a charger that does not have the correct regime can result in anything from an undercharged battery, to a battery that is overcharged and damaged beyond repair.

4 ways a battery can be charged:

  • Simple charging – This is when a battery charger supplies DC power to a battery. The charge is constant and does not vary based on a timer or the current charge of the battery. They are generally cheap but take longer to charge a battery.
  • Trickle charging – This is when a battery charger supplies a low current charge over a longer time period. A battery charger using the trickle charging method can sometimes be indefinitely connected to the battery (depending on the makeup of the battery charger).
  • Timer based charging – This is when a battery charger stops its recharge after a set time. The downside of this method of battery charging is that overcharging may occur, which can cause irreversible damage to the battery.
  • Intelligent charging – The smart charging method usually relies technology that can communicate with the battery and ascertain its level of charge. This allows the charger to balance its load and optimise the way it charges a battery. Charging is stopped when the battery reaches its capacity. A high quality intelligent charger can help keep a battery in a good state of health, which can also extend battery service life.

Different types of batteries require different methods of charging to keep performing at their highest potential.

Nickel Cadmium batteries benefit from being discharged to their minimum cell voltage every now and then. If this is not done, the battery will start to lose capacity, which is called memory effect.

Most Lithium based batteries benefit from frequent charging, which helps maximise performance; frequent deep discharging of the car battery can shorten the battery's life.

Lead acid batteries (used in cars, boats, trucks etc) can be discharged and charged on a fairly frequent basis, without too much degradation in performance, however they should be maintained correctly for optimum output. Lead acid battery life can be extended by some margin if a device is used to float charge the battery (for example your vehicle’s alternator), as this will ensure the battery maintains a full charge indefinitely.

Battery charging checklist:

  • Before charging the battery, check the battery case for cracks. If there is any sign of damage, replace the battery 
  • When charging your battery, make sure there are no flammable objects around - battery gases are very flammable and are easily ignited
  • If you live or visit alpine regions never charge a frozen battery, they can explode if charged while frozen
  • If the battery has vents, check these are clear of fragments or other blockages
  • Always connect the charger to the battery before switching the charger on
  • Switch the battery charger off before disconnecting it from the battery
  • If possible, use a slow battery charge, this is more effective than a rapid charge
  • If you notice the battery getting too hot (around 50 degrees Celsius), stop charging the battery immediately

Battery charging can be a way to increase the longevity and performance of your car battery  however, this is only true if the battery charger being used is compatible with the battery type. If you suspect your battery is extensively damaged or are unfamiliar with the ins and outs of batteries and battery chargers, your NRMA is here to help.

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