Leading the charge

Maximise the service life of a deep-cycle battery by recharging it smarter, not harder

A high-capacity battery is a practical way of supplying off-grid power, whether that's for equipment that runs off 12VDC, or with an inverter to deliver 240V. If you're planning to recharge it from the mains, you'll find a spectacular array of charging options.

The way you recharge your battery can have a dramatic effect on its service life, and if you're planning to recharge LiFePO4 (lithium iron phosphate) batteries as well as SLA (sealed lead-acid) or gel-type batteries, choose a charger that can handle both. Some models are even designed to replenish up to three batteries simultaneously.

A multi-stage charger maintains battery health by cycling through different charging rates in response to a battery's level of discharge. This normally involves starting with a low charging current ('soft start') when the battery is heavily depleted, moving to 'bulk' charging mode at the nominal voltage. Once the battery is close to full charge, the current levels off again to 'float' stage, preventing damage through overheating.

Easily confused with the previous category, multi-state charging is not a spelling error, although the two concepts do overlap somewhat. In addition to having multi-stage options, this type of charger can be set for different charging states, such as desulphation or reconditioning, allowing it to improve the functioning of a battery that’s been heavily used.

Describing a charger as intelligent simply means it has sensor functions and onboard microprocessor control to detect the battery's voltage and temperature, evaluate its condition and adjust charging current to ensure optimal battery health.

See below for a detailed guide to charging high-capacity batteries.

- November 2019

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A Guide To Charging High Capacity Batteries


Australians consume over 352 million batteries each year! Over 271 million of these are disposed of, with the rest recharged for ongoing use.*

Let's face it, our reliance on batteries to power up our everyday lives won't be waning anytime soon! One of the most common batteries we use are sealed lead acid (SLA). Invented in the late 18th century**, they're the oldest type of rechargeable battery. SLA batteries are popular due to their relatively large power-to-weight ratio - they're able to produce a large amount of current over a very short period of time. They also have a long service life with a high discharge rate, meaning they're able to discharge and charge many times over. This makes them extremely cost efficient, which adds to their appeal.

SLA batteries can be used for standby power or emergency power back-up requirements where mains power is cut off. Examples of uses include security and alarm systems, lighting, and computer server back-up. However, you're probably more familiar with SLA batteries as cyclic power sources, for starting the motors of cars, trucks & motorcycles, or storing excess power generated by solar systems.

Almost all batteries naturally discharge without even being connected to something. SLA batteries will only recharge a certain number of times before they wear out, but proper care will maximise their lifespan. Lifespan is determined by the type of battery, how charge is drawn & restored, and conditioning. Let's take a closer look at what you need to know about SLA battery chargers:


If you're using the battery as a power back-up solution then the battery discharge will be nominal. When used as a back-up solution, time is of the essence! If the battery is disconnected from mains power for too long, it will discharge too much and will need replacing. Depending on how your system is set-up, you may or may not be able to use a battery charger to prevent the SLA battery from discharging too much. Battery chargers really come into their own when the SLA battery is used as a cyclic power source and - for whatever reason - hasn't or can't properly recharge as it normally would. A good example of this is an automotive battery. Power is drawn from an automotive battery when assisting the motor to start. It's also used to provide power to other components within the vehicle, such as entertainment systems, lights, air conditioning, alarms, and electronic windows. It's common for a number of these components to continue drawing power long after the ignition has been switched off. The power draw is replenished whilst driving, but not when the vehicle engine is switched off.


Generally most SLA batteries provide power for a nominal time and recharge when plugged in again to 'surface' charge. However, the discharge of the battery can reach a point where surface charging won't provide enough charge. In that instance, you will need a battery charger which is suited to your SLA battery's voltage, level of discharge and any special requirements (such as outdoor charging).


Look at the voltage of the battery you're planning on charging. The output voltage of your charger needs to accommodate the rated voltage of the battery. The majority of Jaycar's battery chargers accommodate two or more battery voltages. Our best selling 15A Intelligent Charger (MB3623) is suitable for 6, 12 & 24V batteries, with a 2A, 7A or 15A output. It's ideal for anyone who has a number of different batteries to accommodate.


Batteries have a tough exterior, but inside their electrolytes are fragile and need to be handled with care! The level of charge a battery has should determine what kind of charging method or 'stage' is applied to it. In the 'soft start' stage, a very low current is applied until the battery voltage reaches a normal charging condition. The 'bulk mode' stage delivers the battery the majority of its charge - up to 80%. Once a battery is close to full charge, the charger moves into the 'float' stage, delivering a minimal charge until the battery reaches 100% capacity. The 'pulse mode' stage is ideal for instances where your battery will not be used for a long period of time. In 'pulse mode' the charger monitors and maintains the battery at 95-100% capacity. Our 800mA 6 & 12V Charger (MB3519) detects when the battery is fully charged and reduces current, then monitors charge levels and charges when appropriate.

Automatic Detection

Some chargers will offer only 1 or 2 stages, whilst some of our multi-stage chargers offer up to 9! They all automatically detect a battery's charge level, select the right stage and apply the charge - taking the guesswork out of it for you. You shouldn't ever set-and-forget, but an automatic charger means you don't have to monitor the charge the entire time. Crude battery chargers that simply jam power into the battery will shorten the life-span of your battery, and in extreme cases, cause overheating or physical damage.


Most of our chargers offer some sort of protection to prevent damage to your battery. This includes short circuit and wrong polarity protection, IP65 ratings (barriers to dirt and moisture), anti-spark, and over current/voltage/heating protection.

Additional Features

Some chargers are classified as high power, meaning they apply the bulk mode charge stage extremely quickly. Our 12 & 24V 9-Stage charger (MB3607) includes output leads fitted with Anderson connectors, for ease of connecting to existing wiring.

Understanding your battery's discharge and recharge requirements, and avoiding heavy discharge (either in use, or sitting disconnected) will help you extend the life and value you get from each battery.  Our team can run through the range of battery chargers with you to find the one that best suits your needs - visit us in store or online today!

* batteryrecycling.org.au PDF
** wikipedia.org Lead Acid Battery


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