Electronics: How to retrofit charging options for mobile phones, cameras and more
Ralf Marquard
· 06.11.2024
More and more on-board devices are using USB interfaces, which were originally developed for the exchange of digital data. These interfaces were intended to replace the various plug connections previously used in computer technology. Nowadays, a USB interface enables smooth data transfer between a PC and a printer, a monitor, an external hard drive or a USB stick. The first version of USB was introduced in 1996 and had a data transfer rate of 12 megabits per second. The current standard, USB 4v2, offers an impressive 80 gigabits per second. In addition to data transfer, the system can also be used to charge devices.
USB port indispensable for many devices
Today, the smartphone is an indispensable everyday companion on board. But tablets, netbooks, torches, jukeboxes, headphones, cameras, razors and much more are also taken along when travelling. These devices are usually charged via the USB port. However, there are a variety of plug types, charging voltages, currents and outputs that need to be taken into account.
It all started with the A-type plug, which is still commonly found. USB-B, mini-USB or micro-USB plugs are also common. The latest generation is the USB-C connector. It will also be with us in the future, as the Federal Council cleared the way in April for new small devices in Germany to only be sold with USB charging options that have a USB-C socket from the end of the year. The same will apply to laptops from 2026. The iPhone 15 also has this USB-C interface. Previously, Apple worked with Lightning connectors, for which there are charging cables with USB-A or -C plugs on the source side (power supply unit, charging module, USB socket).
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As far as cables are concerned, it is advisable to use the original accessories wherever possible. Or buy high-quality branded products to ensure operational reliability and fast charging.
USB 1.0 already supplied current, but at 0.1 amps it was quite low. With USB 2.0 it is up to 0.5 amps and with USB 3.1 (Gen. 2) a maximum of 3.0 amps, in each case at a nominal voltage of 5 volts. The PD (Power Delivery) standard, which works with USB-C ports, has changed a lot in recent years. Different voltages from 5 to 20 volts and a maximum current of 5 amps (max. 100 watts) are now possible in the "Standard Power Range". The latest versions, "Extended Power Range", even support outputs of up to 240 watts at 48 volts.
With the USB-C-PD standard, the devices communicate according to a predefined protocol: The consumer tells the charger what it needs and then checks whether the charge works. The other USB variants also "talk" to each other and agree on a current level.
A typical charging power for mobile phones, for example, is 5 watts. However, there is often the option of fast charging with a higher output. These types of charging (Dash Charge, Quick Charge, Fast Charge, etc.) are supported by modern smartphones. The systems are generally downward compatible. The options offered by your mobile phone can be found in the operating instructions for the device.
In practice: If you are connected to shore power, you can use the power supply units supplied with your mobile devices. It is also possible to install 230-volt sockets that also have USB sockets. An inverter that generates alternating voltage (230 volts) for the socket from the direct voltage (12 or 24 volts) of the vehicle electrical system can also provide good service. However, it is important to ensure that the inverter generates a clean sine wave voltage. In some cases, electronic devices cannot cope with a "modified sine wave", as generated by some simple inverters.
Powerbank as a power source independent of the vehicle electrical system
Powerbanks are available in a wide variety of capacities. If you want to charge your mobile phone occasionally, a capacity of 5,000 milliampere hours is usually sufficient. If you also want to charge your laptop or tablet, power banks with a capacity of around 20,000 milliampere hours or more are ideal. A jump-start power bank that is suitable for emergency starting of combustion engines and also has USB ports is ideal for on-board use.
The most commonly used charging option is probably the USB socket or the adapter for the 12-volt socket. Adapters are quite inexpensive, but are more susceptible to vibration due to the additional contact connection and are also not as well protected against moisture. USB sockets, which are available from numerous suppliers, are better. We will focus mainly on products from the boat accessories range.
Which socket should be installed where? Conventional models are sufficient below deck. On deck, water-protected versions should be used, for example with IPX4 or even IPX6. If there is already a 12-volt socket on board, this can easily be replaced by a USB socket. It may be necessary to enlarge the installation hole with a step drill. Alternatively, surface-mounted sockets are available that are simply attached with several screws.
Devices on board often still have charging cables with USB-A plugs, so the sockets should have a corresponding socket. The same applies to USB-C, especially if you want to use the power delivery option. Note on power: If 36 watts are specified for a socket, for example, this is sometimes the total power.
Induction panels instead of USB sockets
A completely different, elegant charging option is the induction field. As in many car storage compartments, induction fields can also be installed on boats. Mobile phones must be Qi-compatible for this charging method. Some tablets also offer this option. With this charging method, an alternating voltage generates a magnetic field in a coil in the induction zone, which in turn flows through the charging coil in the mobile phone and induces an alternating voltage there. The same principle can be found in electric toothbrushes, for example.
On-board options for induction charging of mobile phones and tablets are available from Scanstrut, for example: these are fixed holders that are screwed on somewhere, built-in panels or storage compartments.
Conclusion: If you don't use your mobile phone excessively, a normal socket is fine. The adapter plug from 12 volts to USB can also be used below deck. If you want to charge your mobile phone quickly or also supply a tablet, netbook or laptop with power, more powerful versions with USB-C power delivery are recommended (see also the recommendations of the device manufacturers). Induction charging surfaces that can be installed in storage compartments are an elegant but more expensive solution for mobile phones.
