A 12V 120Ah lithium battery will typically power a standard 12V compressor fridge for between one and three days, run LED campsite lighting for the better part of a week, and keep a fan circulating air for roughly 20–40 hours, all without any recharging input. Add a solar panel into the equation, and those figures improve considerably.
That is the short answer. But the more useful question is: how long will your setup actually last on your trip? That depends on which appliances you are running, how hot it gets, and how efficiently you manage your power. This guide breaks it all down, so you can plan with confidence before you leave the driveway.
What Can a 120Ah Lithium Battery Actually Power? A Quick Runtime Reference
How to Read a Runtime Estimate: Amp-Hours vs Watt-Hours Explained
A 120Ah battery holds 120 amp-hours of energy at 12 volts. To calculate how long a given device will run on it, divide the battery’s usable capacity by the device’s current draw.
Most devices are rated in watts. To convert watts to amps, divide by the voltage:
Amps = Watts ÷ Volts
So, if a 50W fridge draws roughly 4.2A at 12V, you need to divide 96Ah (the usable capacity at 80% depth of discharge) by 4.2A. You’ll get approximately 22.8 hours of continuous runtime before accounting for the fridge’s duty cycle.
120Ah Battery Runtime at a Glance: Key Appliances and Estimated Hours
| Appliance | Approximate Draw | Estimated Runtime (96Ah usable) |
|---|---|---|
| 12V compressor fridge (40–50W) | 3–5A average | 19–32 hours |
| LED strip lighting (20W) | 1.7A | 56 hours |
| USB charging (phone, tablet) | 1–2A | 48–96 hours |
| 12V fan (20–30W) | 1.7–2.5A | 38–56 hours |
| Laptop via 12V socket (60W) | 5A | ~19 hours |
| Small inverter (150W load) | 14–16A | ~6 hours |
These are estimates based on continuous use. Most setups run multiple devices simultaneously, so real-world runtime will be shorter than any single-device figure.
VoltX 12V 100Ah Blade Lithium LiFePO4 Battery
How Usable Capacity Affects Your Real-World Runtime
LiFePO4 lithium batteries, like the VoltX 12V 100Ah Lithium Battery, can technically be discharged to 100%, but most manufacturers, including the guidance across Outbax’s lithium range, recommend limiting discharge to 80% to preserve long-term cycle life. That gives you a working figure of 96Ah from a 120Ah pack. In most camping and caravanning contexts, that is still a substantial amount of energy, far more than you would get from an equivalent AGM battery, which should only be discharged to 50%, giving just 60Ah of usable capacity.
Here’s what one of our customers said about this battery:
“Quick delivery. Very happy with the battery so far. Much better than the lead acid it replaced. Heaps of power available in comparison. Very impressed.”
How Long Will a 120Ah Lithium Battery Run a 12V Fridge, Lights and Fan?
12V Compressor Fridge Runtime: What to Expect in Australian Conditions
A 12V compressor fridge is almost always the biggest power draw in a camping or caravanning setup. How hard it works depends on two things: the ambient temperature and how often the lid is opened.
In mild southern Australian conditions (under 25°C ambient), a good-quality 40L–60L compressor fridge will typically run at a 30%–40% duty cycle, meaning it is only actively cooling for about a third of the time. At that rate, a 120Ah lithium battery can realistically power the fridge alone for 40–50 hours.
In north Queensland, the Northern Territory, or the Pilbara during summer, ambient temperatures regularly exceed 35°C. Fridge duty cycles can climb to 60%–80%, and your runtime could drop to 18–24 hours in isolation. If you are heading into tropical or outback heat, this is the single biggest factor to account for when sizing your battery.
The Outbax 120Ah LiFePO4 Lithium Battery is well-suited to three-season and southern touring, powering a fridge comfortably over a weekend trip. For full-time remote travel in hot climates, a larger pack is worth the investment.
LED Lights and USB Charging: How Long Before the Battery Is Flat?
LED lighting is one of the most efficient consumers you can run off a 12V battery. A standard camp lighting setup drawing 15–20W will barely put a dent in a 120Ah pack. At 20W, you are pulling roughly 1.7A, meaning the battery could theoretically power the lights alone for 56 hours. In practice, running lights for four hours each evening, you would have over two weeks of illumination from a single charge.
USB charging for phones, tablets, and cameras draws 5–15W. Even charging two devices simultaneously for several hours a day barely registers against a 120Ah reserve.
Running a Fan, Inverter or Other High-Draw Devices
A 12V camping fan running at medium speed draws 20–30W, giving you 38–56 hours of runtime on a 120Ah pack. That is comfortable for a long weekend.
Inverters are a different matter. The inverter itself draws power even before you factor in the load connected to it. A 150W device running through a 300W inverter can pull 14–16A from the battery, cutting your runtime to around six hours. Use inverters sparingly if battery longevity is a priority on multi-day trips.
Voltx 12V 100Ah Slim Lithium LiFePO4 Battery
Five Factors That Affect How Long Your 120Ah Battery Will Last
Temperature, Terrain and Trip Length: Australian-Specific Considerations
Heat increases fridge load, which is the single largest draw in most setups. Cold can also reduce battery capacity temporarily, though this is less of a concern in Australian conditions. Remote terrain means no access to mains power for topping up, making your battery reserve critical. A weekend trip in the Grampians requires a different approach from a two-week lap of the Gulf Country.
Depth of Discharge and Battery Chemistry: LiFePO4 vs AGM
This is where lithium genuinely separates itself. A LiFePO4 battery, such as the Outbax Slimline 120Ah Lithium Battery, offers approximately twice the usable capacity of an equivalent AGM battery. It also charges faster, handles partial charge cycles without damage, and maintains a flatter voltage curve, meaning your devices receive consistent power until the battery is nearly depleted, rather than slowly losing performance as voltage sags.
At low, steady loads, a LiFePO4 battery such as the VoltX 24V 100Ah Pro LiFePO4 Battery can deliver 120+ hours of runtime. An equivalent AGM battery under the same conditions provides roughly 56 hours before hitting its 50% discharge limit. Over a few seasons of regular use, lithium’s longer cycle life also makes it more cost-effective despite the higher upfront price.
Here’s what one of our customers said about this battery:
“Nice light weight alternative to lead acid batteries. Previously bought one of these exact batteries 3 years ago, unfortunately didn’t last the abuse on a boat powering a 80lb minn kota, Hopefully this new one does. These batteries do charge quickly and hold charge for a considerable time.”
Charging Sources: Does Driving or Solar Top-Up Change the Equation?
Yes, significantly. A 200W solar panel in good Australian sunlight can generate 60–80Ah per day, which is enough to meaningfully offset or even exceed what a fridge draws. Driving for three or four hours also charges a secondary battery via a DC–DC charger. If you have either of these inputs, your effective runtime is no longer limited by the battery’s stored capacity alone.
VoltX 12V 100Ah Lithium LiFePO4 Battery
Is 120Ah Enough—or Should You Consider a 200Ah Lithium Battery?
When a 120Ah Battery Is the Right Choice for Weekend Camping or 4WD Day Trips
For most weekend campers running a fridge, LED lighting, and phone charging with or without a small solar panel, a 120Ah lithium battery is sufficient. You will finish a three-day trip with reserve capacity to spare under typical conditions.
When Upgrading to a 200Ah Lithium Battery Makes Sense for Caravanning or Extended Travel
Longer trips, hotter climates, and higher appliance loads all point toward a larger battery. If you are running a caravan with a compressor fridge, lighting, a water pump, and occasional inverter use for a week or more without reliable solar, a 120Ah pack will be stretched. The Outbax VoltX 12V 200Ah Pro LiFePO4 Battery provides 160Ah of usable capacity—enough to power the same setup for significantly longer between charges. It is a more sensible foundation for a touring caravan battery system.
Running Two Batteries: The Case for a 4WD Dual Battery Setup
Many serious 4WD tourers run dual 120Ah batteries rather than a single large pack, giving them 240Ah total capacity spread across two independently managed banks. If you go this route, housing each battery in a quality protective enclosure is essential. The Outbax Battery Box is designed specifically for 12V lithium setups, with ventilation, cable management, and rugged construction suited to corrugated outback tracks.
VoltX 48V 100Ah Pro Lithium LiFePO4 Battery
How to Extend Your 120Ah Battery’s Runtime with Solar and Smart Charging
How Many Solar Panels Do You Need to Keep a 120Ah Battery Topped Up?
A single 200W panel in most Australian conditions will generate between 60 and 100Ah on a clear day. Paired with a 120Ah battery, that is often enough to run a fridge continuously without drawing down your reserve at all. Two panels virtually eliminate the need for any other charging source during a typical touring trip.
MPPT vs PWM Solar Charge Controllers: Which Works Best with Lithium?
MPPT controllers, including VoltX SRNE 12V/24V 20A MPPT Solar Charge Controller, extract more energy from your panels, typically 20%–30% more than PWM controllers under variable cloud conditions, and they are better suited to the voltage profile of LiFePO4 batteries. If you are pairing solar with a lithium battery, an MPPT controller is the right choice. The Outbax MPPT Solar Charge Controller is designed to work seamlessly with LiFePO4 chemistry, managing charge stages correctly to avoid overcharging.
Storing and Protecting Your Battery: Why a Quality Battery Box Matters
A lithium battery is a significant investment. On a 4WD track, vibration, dust and moisture can all cause damage over time if the battery is left exposed. A purpose-built battery box for a lithium battery provides physical protection, keeps terminals secure, and typically includes an Anderson plug outlet for clean, safe connections. It is a straightforward addition that protects your investment for years.
Choosing the Right Lithium Battery for Your Off-Grid Setup
A 120Ah lithium battery is a capable, practical power source for most Australian weekend campers and light caravanners. It will handle a fridge, lighting, and device charging across a three-day trip without difficulty, and with solar input, it will stretch further still.
For those planning longer journeys, touring in hot climates, or running more demanding power loads, the step up to a 200Ah pack makes a meaningful difference. Outbax offers both capacity tiers in LiFePO4 chemistry, along with accessories like battery boxes, MPPT controllers, and solar panels to build a complete off-grid power system. Browse the full range to find the right configuration for how you travel.
