No more empty e-bike batteries: Self-sufficient on the road thanks to fast car charging technology

Assessment by the editorial team

Two hours on the road and enough juice in the power station to charge two e-bikes. The fast car chargers from DJI, Bluetti and co. are fundamentally changing the road trip game for e-mountain bikers. However, those who buy without doing any research are in for a surprise: The alternator of your own vehicle determines how quickly the power station is actually charged during the journey. And not every fast charger is suitable for every power station. If you check this beforehand, you will be self-sufficient. If you don't, you may end up with a 300-euro device that only charges half as fast as promised on your weak alternator. - Max Fuchs, BIKE Editor

It has long been possible to charge e-bikes in a camper or car without having to rely on shore power. Provided that the capacity of the supply battery is sufficient - in other words, it must have at least as much usable capacity as the e-bike battery. If this is the case, most motorhomes with a 230 V power distribution system can easily supply e-MTBs with electricity. After charging, either a solar system on the roof or the alternator during the journey ensures that the battery is topped up again - ideally, both options are available.

The disadvantages are obvious: motorhomes with powerful, pre-installed power setups are expensive, and even a retrofitted system from a specialist can quickly cost a small fortune. Although you can build your own setup yourself, you should have a certain amount of expertise - mistakes in electrical installations in the car can be a fire hazard, especially if 230 volts are involved.

Powerstations as a solution, but not alone!

If you don't yet have a suitable motorhome or the expertise to set up your own, the only option is a power station. However, up to now you have not been truly self-sufficient: charged at home, the capacity is sufficient for one to four battery charges, depending on the model, before the power station itself has to be connected to the mains again. If you want to remain self-sufficient, many power stations can also be operated using solar panels - however, the output of portable modules is hardly sufficient to fully recharge the energy storage system every day, even on sunny days. Not to mention bad weather days. Even 12 V chargers for the cigarette lighter do not offer a serious alternative due to their lack of charging power.

Solar charging: A calculation example

The one we tested Bluetti Apex 300 is also available with a foldable 200 watt solar module for an extra charge. Watt is the unit used to quantify the output of a solar module. Under perfect conditions - midsummer, midday, a cloudless sky and a perfectly aligned module - the panel theoretically delivers 200 watts per hour. If this energy is fed into a sufficiently large power station for four hours, it would be enough to fully charge the 800 Wh battery of an e-MTB once.

In practice, however, things look different: Even under optimal conditions, solar modules usually only achieve 70 to 80 per cent of their rated output. The 200-watt panel then only achieves 140 to 160 watts per hour. If it is cloudy, the yield drops even more drastically - then often only 10 to 25 per cent of the nominal output remains.

Under such conditions, the power station would have to charge for at least 16 hours to charge an 800 Wh e-bike battery. Particularly on the short days in the spring and autumn months, it quickly becomes clear that power stations are only of limited use for supplying e-bikers on road trips for several days - at least if they can only be recharged using solar energy.

Cigarette lighter: wrong calibre

Many power stations also offer a 12 V charging function via the car plug. That's nice. However, most vehicle sockets only charge with 120 to 180 watts. For a 2000 Wh power station, this means over ten hours of driving until it is fully charged again. The cigarette lighter is designed for sat navs, mobile phones or cool boxes, not for recharging a power station in record time.

The solution: Powerstations with quick-charging function directly via the alternator

But enough complaining - time for some good news. Because even with a power-hungry e-bike in your luggage, you can now manage multi-day road trips self-sufficiently. The solution is provided by power stations with special chargers that charge the energy storage unit directly via the alternator during the journey.

These chargers are connected directly to the starter battery with solid cables, usually included in the scope of delivery, and can therefore achieve significantly higher charging capacities. The fast car charger from DJI, for example, charges the associated power station with up to 1000 watts while travelling. In theory, this means that around two hours of driving are enough to fully charge the 2048 watt-hour DJI Power 2000.

However, the maximum amperage of the alternator varies depending on the vehicle model and engine output. Most models generate between 60 and 120 amps. As the theoretical charging power of the alternator in watts is the product of the amperage and the vehicle voltage, approximately 14.8 volts, not all alternators can provide the full 1000 watts of charging power.

But that's not so bad: even with a rather weak alternator with 60 amps, the 1000 W fast charger still achieves 880 watts of charging power at 14.8 volts on-board voltage - taking into account the vehicle's own requirements, such as radio, air conditioning and lighting, this is still enough to fill the Powerstation during a one-and-a-half-hour journey to such an extent that it can fully recharge at least an 800 e-bike battery.

DJI and Bluetti: the two best options for e-bikers

Two particularly exciting devices are emerging on the German market: the DJI Super Fast Car Charger (1000 W) and the Bluetti Charger One (560 W). Both are connected directly to the starter battery with prefabricated cables, both have auto-start and auto-stop - so they charge automatically when the engine is running and stop when it is off. But they follow different philosophies.

DJI Super Fast Car Charger: Maximum speed, one hook

1000 watts of charging power, power regulation in 1-watt increments, automatic recharging to the starter battery when the voltage drops - the DJI is technically the most complete car fast charger on the market. The workmanship is of high quality: all cables are neatly pre-crimped and the leads are encased in tear-resistant cable conduits. That looks professional.

The big but: The DJI fast charger only charges the DJI Power 1000 (649 Euro) and Power 2000 (1099 Euro). Anyone who owns a different Powerstation is left out in the cold.

Bluetti Charger One: brand-neutral, but half the power

The Charger One charges 95 per cent of all power stations on the market - that is its decisive advantage. Anyone who already owns a power station from another brand does not need to replace it. The only basic requirement: a connection for a solar charging cable to plug in the Charger.

Advanced: Instead of a simple fuse, Bluetti installs a circuit breaker - simply flip it instead of changing the fuse. Intelligent voltage monitoring automatically adjusts the charging power to the on-board power supply.

The weakness: 560 watts maximum charging power - half as much as the DJI. Heavily motorised vehicles with powerful alternators cannot fully utilise the maximum charging power with the Bluetti Charger.