The key question is not only how much energy an appliance uses, but also how it connects. A large battery can have plenty of stored energy and still be unable to operate a 240V appliance if no suitable inverter is fitted.
Connection types
| Connection | Typical examples | What the power system needs |
|---|---|---|
| 12V DC Cigarette socket or Anderson-style connector | Portable fridge, 12V lighting, pumps | A suitable fused 12V outlet. No inverter required. |
| USB DC USB-A or USB-C | Phones, lights, cameras and some laptops | The correct USB port, voltage and power-delivery rating. |
| 240V AC Australian mains plug | Kettle, coffee machine, microwave, hair dryer, air fryer | An inverter with enough continuous output and startup-surge capability. |
| Solar input | Fixed panel, folding panel or solar blanket | A compatible solar controller/MPPT, with panel voltage and current inside its limits. |
Power versus energy
Watts (W) describe how quickly power is being used—the immediate demand.
Watt-hours (Wh) describe stored or consumed energy over time—the size of the fuel tank.
Energy used: watts × hours = watt-hours
Example: 20W lighting for 5 hours = 100Wh.
Volts and amps
Voltage (V) is the electrical system pressure. Current (A) is the electrical flow.
Watts = volts × amps
Example: a 2A fridge at 12V draws 24W while its compressor runs.
Cable size, fuse rating and connector rating become increasingly important as current rises.
Battery capacity
Nominal capacity is the headline rating. Usable capacity is the practical energy available after discharge limits and conversion losses.
- 120Ah LiFePO4 at 12.8V ≈ 1,536Wh nominal.
- This adviser assumes about 90% usable for the DIY lithium battery.
- AGM is conservatively modelled at about 50% usable to support battery life.
Inverters and waveforms
An inverter converts battery DC into 240V AC. Its watt rating determines which mains appliances it can run—not the battery's Wh rating.
Modified sine wave is a budget option best reserved for compatible chargers and simple low-power electronics. Pure sine wave more closely reproduces mains power and is preferred for sensitive electronics, motors and broader appliance compatibility.
Rated output, surge and X-Boost
| Rating | What it means | How to use it |
|---|---|---|
| Rated output | Normal continuous inverter power at the intended AC voltage. | The primary number for matching running appliance watts. |
| Surge output | A short burst of genuine additional output for startup demand. | Compare with starting watts for motors, compressors, pumps and tools. |
| X-Boost | EcoFlow voltage management that may operate a compatible above-rated appliance at reduced performance. | Best suited to simple heating loads. It is not extra battery capacity or a replacement for adequate rated output. |
Charging terms
AC charger: charges the battery from a wall outlet.
DC–DC charger: safely charges an auxiliary battery from a vehicle alternator; some include solar MPPT.
MPPT controller: regulates compatible solar-panel output into safe battery charging.
Why a system may fail
- A 240V appliance is selected but the system has no inverter.
- The appliance wattage exceeds the inverter’s continuous rating.
- Startup surge exceeds the inverter’s short-term capability.
- A solar panel is selected but no compatible controller is included.
- The connector, cable or fuse is not rated for the required current.