Charge boosters (DC-DC converters) in boats: When and which ones do you need?

In traditional boat installations, starter and consumer batteries are often simply connected via isolating relays or diodes. However, modern DC-DC charge boosters such as the Victron Orion perform intelligent control tasks: they charge the on-board/service battery with an optimized multi-stage charging profile (e.g., for AGM or LiFePO₄) instead of just with the raw alternator voltage. This results in a more complete and gentle charge for the battery. Important: A DC-DC converter also protects the alternator from overload. Lithium batteries, for example, would draw as much current as the alternator can supply when empty, which can cause permanent overheating and damage. The Orion limits the charging current to a safe value, preventing the alternator from being “worked to death.” In addition, different battery systems (such as lead starter batteries and lithium on-board batteries) can be galvanically isolated and supplied with the appropriate charging voltage without affecting each other.

Victron offers Orion-Tr Smart Chargers in various versions, e.g., 12/12-18A, 12/12-30A, 12/12-50A for 12V-to-12V applications, as well as models for voltage converters between 12V and 24V (e.g., 24/12- or 12/24-converters). Step 1: Select a model that matches the voltage level of your system – i.e., 12/12V for vehicles/boats with a uniform 12V starter and consumer battery, or 24/12V if you need to charge or supply a 12V consumer battery from a 24V electrical system. Step 2: Dimension the charging current. This should match the battery capacity and the desired charging profile. Example: For a 200Ah consumer battery, a charging current of 30-50A is common (approx. 0.2C) – in this case, an Orion 12/12-30 or 12/12-50 would be appropriate. Step 3: Note that several Orion units can be connected in parallel to achieve a higher current. For example, if you have two alternators or require >50A charging current for a large battery bank, two Orion 12/12-30 units connected in parallel can supply ~60A. Step 4: Look for the Smart version (all current Orion-Tr models are Smart), which can be configured via Bluetooth. This allows you to conveniently set the battery type (e.g., lithium with 14.4V charge termination) and, if necessary, control the input via ignition plus.

In boats (especially those with plastic hulls), there is often no common vehicle ground point as in motor vehicles. In this case, an isolated DC-DC converter can be useful. Isolated means that the input and output do not have a common ground – the converter galvanically separates the input (starter battery/alternator) and output (on-board power supply). This prevents ground loops and corrosion currents in the vehicle electrical system, which can be advantageous for sensitive marine electrical systems or metal hulls. Non-isolated converters, on the other hand, have a common negative terminal and are well suited for vehicles or boats that use a common ground strap anyway. They are slightly cheaper, more compact, and more efficient. In short: on GRP yachts without any particular grounding problems, a non-isolated Orion is usually sufficient; however, an isolated one does no harm if you want to be on the safe side. In metal boats (steel/aluminum) or with ungrounded systems, it is better to use the isolated version to avoid leakage currents.

The installation location of the charge booster should be dry and ventilated (electronics do not like constant heat). Use sufficiently thick cables for the connections and secure the input and output lines (Victron specifies the recommended fuse size in the manual, e.g., 60A). The cable lengths between the battery, Orion, and consumer should be kept as short as possible to minimize losses. If your Orion has a remote input, you can connect it to the ignition switch or a D+ signal from the generator, for example, so that the converter only runs when the engine is running – this prevents the starter battery from discharging when the vehicle is stationary. After connecting, please switch on without consumers and measure the output voltage, then switch on the consumers and check whether the charging current flows as expected and nothing overheats. Overall, installing a charge booster is not rocket science, but careful work (correct polarity, tight screw connections, no loose contacts) is essential to avoid malfunctions.