The "go to" battery for both Gen2.5 units — and it moves between them.

The FM+ 650 sits at the intersection of runtime, weight and cost, and is the go-to battery option for both the Gen2.5 Fusion and the MAX+. With 648Wh of capacity, Foil Drive's 43V architecture unlocks powerful, consistent thrust and endurance — for extended surf sessions, upwind and downwind runs, wake riding, pumping, flatwater starts and light eFoiling.

Because it works across both the Fusion and the MAX+, one battery moves between two very different setups. For MAX+ riders this is your highest capacity battery, with plenty of runtime for a full surf session. Fusion riders simply add the FM+ Battery Adaptor for a lighter, more manoeuvrable alternative to the 860.

Details

Gen2.5 battery technology lets you use more of the battery. It performs deeper into the cycle, so on the water you get full power delivery right down to around 10% before you start to notice the sag that every battery eventually shows.

Charging. The FM+ 650 needs a 43V charger, which is supplied with your Fusion or MAX+ system. It averages an 85 minute charge, and includes a Storage Mode that limits charging so you can store the battery for long-term health. We'd recommend storing between 30 and 60% state of charge.

Smart BMS. An intelligent Bluetooth battery management system feeds accurate data to the V3 Controller for clear percentage and status readouts. It also connects to the Foil Drive App, where you can name each battery, track its health and check its state of charge — handy for checking the surf cam and your charge level without getting out of bed.

Tech Specs

• Rated capacity: 648Wh
• Amp hours: 15Ah
• Nominal voltage: 43.2V
• Maximum voltage: 50.4V
• Battery weight: 3.95kg (8.70lbs)
• Battery dimensions: L460 x W125 x H55mm
• Installed dimensions: 540 x 125 x 55mm with the MAX+, 658 x 125 x 55mm with the Fusion
• Nose cone: not required — integrated
• Battery type: lithium-ion
• Water rating: IP69 water and dust resistance
• Certification: UN38.3, CE, FCC, WEEE, RoHS, PSE, IP68, IP69

Indicative runtimes

• eFoil, intermediate: ~31 minutes*
• eFoil, advanced: ~52 minutes*
• Surf, intermediate: ~40–50 minutes**
• Surf, advanced: ~55–70 minutes**

Runtime varies a lot with skill, weight, gear sizing and conditions — treat these as a guide based on real-world averages.

*Based on an 80kg rider, 800cm² wing, 5'0 40L board, throttle around 70%. The intermediate rider has many touchdowns and multiple falls and restarts; the advanced rider has none.

**Based on an 80kg rider, 800cm² wing, 5'0 40L board in 3ft swell with under 5kts of wind. The intermediate rider has high motor reliance and isn't pumping between waves, with many falls and restarts; the advanced rider has medium motor reliance, links some waves by pumping, and has minimal falls.

What's Included

• FM+ 650 Battery
• FM+ 650 Battery carry case

Compatible With

• Foil Drive Assist MAX+
• Foil Drive Fusion (with the FM+ Battery Adaptor)
• 43V Standard Charger
• Foil Drive Battery Caddy (with the FM+ Battery Adaptor)

Not compatible with the Gen2 Assist MAX, which runs 40V.

Expert Advice: This is the battery that finally makes a two-system quiver sensible — buy one, run it on the MAX+ and on a Fusion, or share it with a mate running the other unit. If you're on a Fusion already, remember you'll need the FM+ Battery Adaptor as well; Fusions bought before 23 September 2026 don't include it. Store it at 30–60% between sessions and it will look after you.

It is important to properly care for your Foil Drive battery. Click here to learn about lithium battery use, care and storage.