For trips longer than a single night, or 4WDing during the warmer months, a dual battery setup for a fridge is key to keeping food fresh. With an auxiliary battery, you can keep the fridge on (and beer cold) without discharging your starter battery.
There are a few options for your dual battery setup to run a fridge, from selecting the auxiliary battery and charger to power monitoring using an integrated system or a simple voltage gauge. The right dual battery setup can power a fridge and ensure your camping experience is top-notch.
Pat Callinan On Choosing A Dual Battery Setup For 4x4
Components Of A Dual Battery System For A Fridge
A basic dual battery system to run a fridge includes a second battery for your vehicle and a battery isolator. To recharge your battery on the road in a vehicle newer than 2000, you’ll need a battery charger.
Once you have this basic setup in place, other modifications and upgrades can improve the visibility of your power system. From a smart battery monitor to a complete battery management system, you can connect solar, mains power or charge as you drive for a dual battery system that not only powers your fridge but meets all of your expectations for powering off-grid adventure.
Choosing an auxiliary battery to power a fridge
Selecting the right auxiliary battery depends on your investment, where the battery will be installed, and whether additional weight is a concern.
Engine-bay installation
Lead acid batteries are cost-effective, suitable for engine-bay installation and a great entry-level option that will be able to power a 12V fridge. Calcium batteries are also cost-effective and suitable for engine-bay installation. Calcium batteries are more durable, tolerating higher temperatures, vibration and harsher environmental conditions than lead-acid batteries. Calcium batteries also tolerate a deeper discharge.
Canopy or in-vehicle installation
If your second battery needs to go into a caravan, or van, inside a dual cab canopy or inside the vehicle itself, choose a battery that doesn’t emit harmful gasses or fluids.
Gel batteries tolerate deep cycling, are suitable for installation inside the canopy or vehicle and require precise charging to gain optimal battery life.
Lithium batteries are the pick if weight is critical. These batteries can handle discharge up to 80% but do require precise management to optimise their lifespan. You can choose from a lithium battery installed within the vehicle or a portable lithium battery that you can move to a suitable location in your campsite. There are many advantages of a portable battery over a traditional dual battery system, ultimately it comes down to investment level and lifestyle.
|
Battery type |
Install location |
|
Lead acid |
Engine bay |
|
Calcium |
Engine bay |
|
Gel/AGM |
Canopy |
|
Lithium |
Canopy or in-vehicle |
Battery chargers for a dual battery setup for a fridge
Once you have selected a battery, it’s time to choose from the options for keeping your second battery charged to power a fridge and other appliances.
1. Smart Battery Isolator
A smart battery isolator works in vehicles with a fixed voltage alternator to prevent the second battery from draining the main car battery when the engine isn’t running. A smart battery isolator senses when power is available from another source like solar, or when the vehicle engine is running, isolating the second battery to charge from another power source, or simply to prevent it from draining the starter battery when the car stops.
Older vehicles (generally models built before 2000, but check with your vehicle manufacturer) can typically be installed with a smart battery isolator. Once installed, you can run a 12V fridge from the second or auxiliary battery without concerns that your main starter battery will deplete once the car stops.
2. DC-DC Battery Charger
Newer vehicles have smart and temperature-compensating alternators, and you’ll need a dual battery charger to charge a second battery. DC-DC chargers can also be installed in vehicles with fixed alternators, the advantage over a smart battery isolator is that a DC-DC charger provides more flexibility in how you install your dual battery system.
A DC-to-DC charger will charge an auxiliary battery to 100%. REDARC’s BCDC (battery charger from direct current) chargers can be conveniently installed inside the vehicle next to your second battery. The charger can overcome the current drop from a longer cable.
3. Battery Management System
A complete battery management system gives you ultimate control and visibility over a dual battery setup. This battery charger allows you to charge from any vehicle type, plus you can charge from a solar system and mains power input on
The Manager 30 is a complete battery system that allows power input from AC, DC or solar. The battery management system provides visibility of the state of charge of the auxiliary battery, making it easier to manage discharge and recharge cycles and ensure you have enough power to keep the fridge on overnight and longer.
For even more sophisticated battery management, the Manager Alpha can charge a battery from a combination of vehicle, mains and solar power & has a high current output for large battery banks. This system is recommended if you intend to run a number of devices alongside your portable fridge.
Which dual battery setup is right to power your fridge?
Our dual battery selector tool can help you identify suitable options for charging a dual battery setup to power a fridge and other devices based on your vehicle model, the type of auxiliary battery and whether you have portable solar power.
Frequently asked questions
Will a 12V fridge drain my car battery overnight?
A fridge cycles on and off, consuming power throughout the night. Power usage will depend on temperature, ventilation, seal effectiveness and the contents of the fridge as well as the size and condition of the fridge. Keeping appliances connected directly to the car battery when the car is not running is not recommended as the starter battery could be drained.
Can you run a fridge off a dual battery?
Absolutely. An auxiliary battery for the fridge allows you to leave it running after the car is switched off, without draining the vehicle starter battery. Ideally, you will partially discharge the battery before topping it up by driving and charging from DC power, charging using solar power or charging it up from mains power.
How do I choose the right batteries for my dual battery setup?
We recommend lithium for your second battery, especially if installed inside the vehicle cabin or canopy. Lithium batteries can handle up to 80% discharge, are lighter, and maintain a higher output voltage during discharge cycles.
AGM or Gel batteries won’t leak, spill and are sealed or emit harmful gas, and are more cost-effective and compact. Compare auxiliary battery options to dive deeper into engine-bay options.
