Foil Drive Inline Battery Checker - 40V

The Foil Drive Inline Battery Checker - 40V is a compact diagnostic accessory designed to display the current state of charge and voltage of compatible Foil Drive batteries. Made by Foil Drive, the Australian brand behind the Assist series of electric foil propulsion systems, this checker plugs directly into the battery connector and provides an on-screen readout of remaining capacity. A single press of the power button toggles the display to show the battery's voltage, giving riders a quick way to assess charge status before heading out on the water.

Foil Drive offers the checker in two voltage-specific versions. The 40V model covered here is built for the higher-voltage battery platform, while a separate 28V model serves the brand's lower-voltage lineup. Choosing the correct voltage version is essential — the two are not interchangeable.

• Voltage rating: 40V
• Compatible batteries: MAX Power, MAX Sport, Slim Performance
• Display: On-screen state-of-charge percentage and voltage readout
• Connection: Dual-input inline design (connects between charger and battery, or directly to battery)
• SKU: FD172-1

This accessory is aimed at any Foil Drive rider running a 40V battery — whether on the Assist MAX or Assist Slim platform. It is particularly useful for riders who want to verify remaining charge before a session without relying solely on the charger's indicator light. Because the checker can also be connected inline between the charger and battery during charging, it offers a convenient way to monitor charge progress in real time, though Foil Drive notes the reading can display 5–10% higher than actual charge while the charger is connected. For an accurate readout, the brand recommends unplugging the charger and waiting roughly 30 seconds for the reading to stabilize.

One important usage consideration: the checker draws continuous power when left connected to a battery. Riders should unplug it promptly after checking to avoid draining the battery unintentionally.

Within the Foil Drive accessory catalog, the Inline Battery Checker sits alongside chargers, replacement cables, and other maintenance items that support the Assist system. Its direct counterpart is the 28V Inline Battery Checker, which serves riders on the Standard PLUS, Small PLUS, and Slim Endurance batteries. Together, the two checkers cover the full range of Foil Drive battery platforms. At roughly USD $34, the 40V checker is a low-cost add-on compared to the batteries and motor units it supports, filling a straightforward diagnostic role rather than a performance one.