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Which auxiliary battery do I need?

The honest answer to this question is often, how deep is your wallet or how much do you want to spend?

We could spin various combinations but when it comes to batteries, budget is usually the tipping point when choosing your next replacement auxiliary battery.

With that being said, there are many varieties out in the market, in different sizes, weights and chemistry types which will have some degree of influence in which one you end up choosing for your next super tourer.

Let’s take a closer look.

Standard Lead Acid

Your standard lead acid battery is going to be the friendliest to your pocket, however, is going to require regular maintenance with topping up of electrolytes (using distilled water). They are suitable for various vehicle applications and can be used either as a starting battery as well as a deep cycle battery.

Although not the lightest in weight, they are suitable for engine bay mounting if you don’t have space in your vehicle to install an auxiliary battery.

A great all-rounder, they are a good option if you’re just starting out in this space.


Coming at the same price point as a lead acid battery, the benefit a calcium battery has is that they are maintenance-free because they come sealed and are also readily available. They can also be mounted in an engine bay and be used for starting and deep cycle applications.

They have advantages over lead acid batteries including improved resistance to corrosion, no excessive gassing, less water usage and lower-self discharge. In addition, they have a better tolerance to higher temperatures, environmental conditions, and vibration.

Gel/AGM batteries

Gel/AGM batteries are a little dearer than lead acid and calcium batteries but are still reasonably priced. Some AGM and Gel batteries are not recommended for engine bay mounting as they can’t handle the heat, and if exceeded, can be detrimental to battery life.

They can, however, tolerate deeper cycling than other constructions without dramatically shortening their life.

Both AGM and Gel batteries have a very similar reaction when charging which is why they have the same charge profile, although it is still not recommended to discharge below 50% in order to best extend battery life.

Although maintenance free, AGM and Gel cell batteries do require precise charging and therefore require a charger designed for these battery types.

Lead Crystal

New to the market, lead crystal batteries are going to be more expensive than AGM/Gel batteries but do provide greater advantages, requiring 30% of the total Amp Hour rating in charge current to achieve 100% SOC and can sustain and recover from deep discharge better than the other battery types.

They’re also built tough and robust, can sustain and recover from heavy discharge and are able to accept higher charge currents which allow the batteries to recover faster.


When it comes to auxiliary batteries, Lithium (LiFePO4) are the latest and greatest due to the various qualities and abilities they have over other batteries. But those qualities come at a price. Lithium batteries are considerably lighter than other battery types - up to 1/3 of the weight - are smaller and can maintain a higher output voltage during the discharge cycle.

Whilst most other batteries recommend discharging of no more than 50%, Lithium batteries, on the other hand, can handle up to 20% discharge and have considerably more usable power than all other battery types of the same amp hour rating.

In addition, as lithium batteries can handle a higher charge current, recharge times are greatly reduced when compared to other battery chemistries.

Because of their unique chemistry type, these batteries do require a specific charging profile to ensure you are using them to their full potential.

More power, better performance and a third of the weight, it’s easy to see why lithium batteries are so expensive, but they are sure to transform your rig into a super 12-volt charging beast.

Finding the right battery charging solution

No matter which battery you decide to go with, it’s important you have the right battery charger for your needs. Our range of dual battery chargers, it works with all battery types and will ensure 100% charge.

Ready for your next adventure? Check out our vehicle selector tool now!

Take the REDARC Hilux product tour to find out what products are best for your overlanding, power management and towing needs.