Charging a portable power station from your car
Almost every portable power station can charge from a car's 12 V socket (the "cigarette lighter" outlet). It's handy on a road trip, but slow: the socket and the station's car-charging input usually limit it to around 100 watts or so, so a large station can take a full day of driving to fill.
How long it takes
The 0.9 allows for losses in the cable and the station's charger. Your manual lists the car-charging input, often as volts and amps, such as 12 V at 8 A (96 W) or 10 A (120 W). Many car sockets are fused at about 10–15 A, and the station's own input limit is usually the lower of the two.
| Capacity to fill (from empty) | At 100 W | At 120 W | At 300 W (DC-DC or alternator charger) |
|---|---|---|---|
| 300 Wh | about 3.3 hours | about 2.8 hours | about 1.1 hours |
| 500 Wh | about 5.6 hours | about 4.6 hours | about 1.9 hours |
| 1,000 Wh | about 11.1 hours | about 9.3 hours | about 3.7 hours |
| 2,000 Wh | about 22.2 hours | about 18.5 hours | about 7.4 hours |
Example: a 1,000 Wh station on a 100 W car input needs about 1,000 ÷ (100 × 0.9) ≈ 11 hours of driving from empty. Most people top up partway instead. Two hours of driving adds roughly 2 × 100 × 0.9 = 180 Wh.
Why the car socket is slow
Power is volts times amps. At around 12–14 V, even 10 A is only 120–140 W, compared with several hundred to over a thousand watts from a wall outlet on many stations. The thin wiring behind a dashboard socket isn't made for more. Plugging into a higher-current socket doesn't help if the station's car input is the limit. Use the watts to amps calculator to convert your manual's figures.
Faster options
- Dedicated alternator or DC-DC charger: a charger wired to the car battery with heavy cable and its own fuse, often several hundred watts. Some power station makers sell one for their models. It needs proper installation, with the cable sized for the current (see the 12 V wire size calculator).
- Inverter on the car battery: an inverter clamped to the battery lets the station use its faster AC charger, but you lose 10–15% in the double conversion, and the car's alternator has to keep up. Only do this with the engine running and an inverter wired and fused for the current.
- Solar on the roof or at camp: combine car charging while driving with solar while parked. See the solar charging time calculator.
Protect the car battery
- Charge while the engine runs. A starting battery holds limited energy, and draining it can leave you unable to start the car. Many cars switch the socket off with the ignition. Others leave it on, so unplug the station when you park unless the station or charger has a low-voltage cut-off.
- Don't idle in an enclosed space. Never run the engine in a garage to charge, even with the door open: exhaust contains carbon monoxide.
- Check the fuse rating. If the station's car input draws close to the socket's fuse rating, the fuse may blow on long drives. The owner's manual lists socket fuse ratings.
- Heat. A station in a closed car in summer sun can get too hot to charge. Most will pause until they cool down.
Frequently asked questions
Can I charge a power station in my car while parked?
Only for short periods, and only if the socket stays powered. The car battery is not deep-cycle and usually holds far less usable energy than the station you're trying to fill. Run the engine, or use solar.
Does car charging work with 24 V trucks?
Many power stations accept a range of DC input voltages, often up to around 24–30 V or more. Check the manual's input voltage range before plugging into a 24 V socket.
Is it bad for the power station?
No. Car charging is a low, gentle current for the battery. Use the cable supplied or one rated for the current, and push the plug fully into the socket so it doesn't get hot.