There's nothing worse than reaching for a cold drink after setting up camp, only to find it lukewarm. A dead battery doesn't just mean warm beer—it means spoiled meat, wasted supplies, and a trip that's gone sideways before it properly started.
Choosing the right size lithium battery for your camping fridge isn't complicated, but it does require understanding a few basics. The answer depends on your fridge size, how long you're staying off-grid, and the conditions you'll face. This guide walks through the practical calculations so you can make a confident decision and keep your food fresh for the entire trip.
Understanding Fridge Power Consumption Basics
Before calculating battery requirements, you need to understand three terms that appear on every fridge specification sheet.
Watts (W) measure the rate of energy use when the compressor is running. Think of it as how hard your fridge is working at any given moment.
Amps (A) indicate how much electrical current the fridge draws from your battery. This is the figure you'll use for calculations.
Amp hours (Ah) represent your battery's total capacity—essentially, its fuel tank. A 100Ah battery like the VoltX 12V 100Ah LiFePO4 battery can theoretically deliver 1 amp for 100 hours, or 10 amps for 10 hours. This metric determines how long your battery can power your fridge before needing a recharge.
Why Duty Cycle Changes Everything
Here's what many campers overlook: your fridge compressor doesn't run continuously. It cycles on and off throughout the day, typically operating only 25% to 50% of the time. This is called the duty cycle, and it dramatically affects your actual power consumption.
A fridge rated at 2.5 amps doesn't draw 2.5 amps every hour. If it runs with a 40% duty cycle, you're actually using closer to 1 amp per hour on average. Several factors influence the duty cycle. Hot ambient temperatures force the compressor to work harder. Opening the lid frequently lets cold air escape. Running the fridge half-empty means more air to cool. Understanding this helps you estimate realistic power needs rather than worst-case scenarios.
Key Factors That Influence Your Battery Choice
Your ideal battery size depends on several variables working together.
Fridge size and type make the most significant difference. A compact 25-litre camping fridge draws considerably less power than a 75-litre dual-zone camping fridge freezer. Chest-style fridges typically maintain temperature more efficiently than upright camping fridges because cold air doesn't spill out when you open them.
Ambient temperature affects power consumption dramatically. A fridge working in 40°C outback heat might run with a 60% duty cycle, while the same unit on a cool mountain evening might only cycle 25% of the time. Plan for the conditions you'll actually encounter.
Your usage habits matter more than most people realise. Pre-cooling your fridge and contents at home on mains power before leaving reduces the initial workload significantly. Keeping the fridge full (even with water bottles to fill empty space), minimising lid openings, and positioning it in shade with good ventilation all extend battery life.
A Simple Guide to Battery Types for Camping
Two battery technologies dominate the camping market, each with distinct advantages.
AGM Deep Cycle Batteries
AGM (Absorbent Glass Mat) batteries have been the reliable workhorse for Australian campers for years. They're vibration-resistant, maintenance-free, and more affordable upfront than alternatives.
The trade-off is weight and usable capacity. AGM batteries are heavy, and you should only discharge them to 50-60% of their rated capacity to maintain longevity. A 100Ah AGM battery effectively provides 50-60Ah of usable power. For weekend campers or those on a tighter budget, AGM remains a solid choice.
Lithium (LiFePO4) Batteries
Lithium batteries like the VoltX 12V 190Ah Pro Lithium LiFePO4 Battery have transformed camping power setups. They're significantly lighter than AGM equivalents—often half the weight—and deliver 80-100% of their rated capacity safely. They also charge faster and last considerably longer, typically handling 2,000+ charge cycles compared to 300-500 for AGM.
While more expensive than other battery chemistries, LiFePO4’s higher upfront cost pays off over time, particularly for frequent campers. Outbax stocks a range of lithium deep cycle batteries suited to various setups and budgets.
Here’s what one of our customers said:
“Great battery at a reasonable price. I did heaps of research, watched endless YouTube teardown videos and got more confused than before. I decided on the VoltX 200ah battery due to the great price and several reviews that had good things to say about other VoltX batteries, plus it is less than half the weight of my old AGM set-up. So far it seems to be all that it is advertised as. I am running it in my canopy with a 20lt fridge permanently running. I set up a smart shunt and the info is that the battery hardly moves while running the fridge.”
Power Stations
For campers wanting simplicity, portable power stations combine a battery, an inverter, and multiple outlets in one unit. They're convenient and user-friendly, though generally more expensive per amp-hour than separate components.
| Feature | AGM Battery | Lithium Battery |
|---|---|---|
| Usable Capacity | 50-60% | 80-100% |
| Weight | Around 30kgs | Around 12kgs |
| Lifespan | 300-500 Cycles | 2,000+ Cycles |
| Upfront Cost | Lower | Higher |
| Long-Term Value | Moderate | Excellent |
How to Calculate Your Battery Size: A Step-by-Step Method
Here's a straightforward calculation method you can apply to your specific setup.
Step 1: Find Your Fridge's Power Draw
Check the compliance plate on your fridge or consult the manual. Look for the amp draw figure—typically between 1.5A and 5A, depending on fridge size. For this example, we'll use 2.5A (common for a 40-litre fridge).
Step 2: Calculate Daily Consumption
Multiply the amp draw by 24 hours, then by your estimated duty cycle.
Example: 2.5A × 24 hours × 40% duty cycle = 24Ah per day
Step 3: Multiply by Days Off-Grid
If you're camping for three days without recharging:
Example: 24Ah × 3 days = 72Ah total requirement
Step 4: Adjust for Battery Type
This is where battery chemistry matters. For a 72Ah requirement:
- AGM battery (50% usable): You'd need approximately 140-150Ah capacity
- Lithium battery (80% usable): You'd need approximately 90-100Ah capacity
Quick Reference Table
| Fridge Size | Avg. Amp Draw | Daily Use (40% Duty) | Min. AGM Battery | Min. Lithium Battery |
|---|---|---|---|---|
| 40 Litre | 2.5A | ~24Ah | 100Ah | 60Ah |
| 60 Litre | 4.0A | ~38Ah | 150Ah | 100Ah |
Extending Your Trip with Solar Power Options
Solar panels transform battery management for longer trips. Rather than carrying enough battery capacity for your entire stay, solar recharges your battery during daylight hours, replacing what the fridge consumed overnight.
Here’s a practical rule of thumb: a 120W-200W solar panel pairs well with a 100-120Ah battery running a 40-60L fridge. This setup can maintain your battery indefinitely in good conditions, or significantly extend capacity during overcast weather. For efficient charging, an MPPT controller (Maximum Power Point Tracking) extracts more usable power from your panels than basic PWM controllers—particularly valuable in less-than-perfect sunlight.
Outbax offers solar blankets and portable panels designed specifically for camping applications, making it straightforward to add solar to your existing setup.
Here’s what one of our customers said:
“I have set these panels up on my old man's camper and to date they haven’t let him down. He’s running an Engle Fridge. It's keeping his beer etc cold so he’s very happy.”
Final Thoughts on the Right Power Setup
There's no universal answer to battery sizing—the right choice depends on your fridge, your trip length, and your budget. However, a few principles apply across the board.
- Slightly oversize your battery. Having a buffer provides peace of mind and accounts for unexpected variables like hotter weather or a longer stay.
- Match your battery to your camping style. Weekend warriors might find AGM perfectly adequate. Regular tourers will likely appreciate lithium's weight savings and superior capacity.
- Consider solar for extended trips. Even a modest panel setup dramatically extends your off-grid capability.
Properly matched equipment transforms camping confidence. Work through the calculations, account for your specific conditions, and you'll never face a warm esky again. Getting your power system right means less worry about logistics and more time enjoying the trip.
Need to buy gear? The Outbax range includes deep cycle batteries, portable power stations, and solar accessories to suit setups from casual weekenders to serious off-grid adventurers. Check your options today and pick the best fit for your next adventure.
