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Sheet updated September 2026
The Foil Drive FM+ 650 Battery is the 648 Wh lithium-ion battery from the FM+ range. It's the benchmark battery for the Assist MAX+, and it also fits into a Fusion with the FM+ Battery Adaptor. Foil Drive engineered this battery to hit the sweet spot between range, weight, and price. It is built on the 43 V platform. It delivers consistent thrust for long surf foil sessions, upwind runs before a downwind, wake, pumping, flat water starts, and light efoil. The battery and nose cone are a single molded, waterproof piece.
KEY INFORMATION
FOIL DRIVE FM+ 650 BATTERY - 648 Wh foil assist battery
What we like
- 648 Wh: This is the largest capacity available for the Assist MAX+. It provides enough power for a full surf session, according to Foil Drive.
- One battery, two units: It fits directly into the Assist MAX+. It also fits into the Fusion with the FM+ Battery Adaptor.
- Integrated nose cone: The battery and nose cone are molded as a single, IP68 and IP69 waterproof piece. This centers the weight directly above the foil.
- Power to the end: Gen2.5 technology maintains full power down to approximately 10% charge.
- Charges in 85 minutes: Use the 43 V charger for a quick recharge. A storage mode limits charging to preserve the battery.
- Bluetooth tracking: The BMS sends the percentage to your V3 remote and the Foil Drive app.
Use
Foil assist • Surf foil • Downwind • Efoil
Available sizes
Color
Black
Included / Not included
✔️ Included: FM+ 650 Battery and its transport bag
❌ Not included: 43 V charger, Foil Drive unit, FM+ Battery Adaptor
DETAILED DESCRIPTION
Capacity, range, and compatibility
The FM+ 650 delivers 648 Wh and 15 Ah, with a nominal voltage of 43.2 V. Foil Drive provides benchmarks measured with an 85 kg rider, an 800 cm² wing, and a 5'0 40 L board. Expect approximately 29 minutes in efoil for an intermediate rider and 48 minutes for an advanced rider, in flat water with 70% throttle. In surf foil, with 3-foot swell and less than 5 knots of wind, you'll get 40 to 50 minutes for an intermediate and 55 to 70 minutes for an advanced rider. These figures vary greatly depending on your weight, equipment, and conditions. On the Assist MAX+, the battery fits directly. It offers the largest capacity available. On a Fusion, it mounts with the FM+ Battery Adaptor for a lighter, more maneuverable setup. It is not compatible with the Assist MAX Generation 2.
Design, charging, and storage
The battery and nose cone form a single molded and sealed piece. This design ensures better water flow, increases strength, and positions the weight directly above the foil's center of lift. Internal thermal management maintains consistent thrust throughout the discharge. Charging is done with the 43 V charger supplied with the Fusion and Assist MAX+. This takes an average of 85 minutes. The storage mode limits the charge before a long break. Foil Drive recommends storing the battery between 30% and 60%. The Bluetooth BMS transmits the charge level to your V3 remote and the Foil Drive app. The battery is shipped charged to less than 30%. Recharge it before your first session.
SIZE GUIDE
| Size | Capacity and Weight |
|---|---|
| One size | 648 Wh, 3.95 kg |
TECHNICAL SPECIFICATIONS
| Specifications | |
|---|---|
| Type | Foil assist lithium-ion battery, FM+ range |
| Capacity | 648 Wh, 15 Ah |
| Voltage | 43.2 V nominal, 50.4 V max |
| Weight | 3.95 kg |
| Dimensions | 460 x 125 x 55 mm |
| Mounted dimensions | 540 x 125 x 55 mm on Assist MAX+, 658 x 125 x 55 mm on Fusion |
| Nose cone | Integrated |
| Charge | 43 V charger, 85 min average, storage mode |
| Watertightness | IP68 and IP69 |
| Certifications | UN38.3, CE, FCC, WEEE, RoHS, PSE |
| Compatibility | Assist MAX+, Fusion with FM+ Battery Adaptor; not compatible with Assist MAX Gen 2 |
| Delivery | Battery and transport bag |
FAQ - FOIL DRIVE FM+ 650 BATTERY
Foil Drive estimates 40 to 70 minutes for surf foil sessions and 29 to 48 minutes for efoil, depending on your skill level. These figures are based on an 85 kg rider using an 800 cm² wing. Your weight, equipment size, and the conditions will significantly impact these times.
This battery fits directly into the Assist MAX+. For the Fusion, you'll need the FM+ Battery Adaptor. It is not compatible with the 2nd generation Assist MAX, which runs on 40 V.
We're a dedicated kite, wing, and foil shop located in Pornichet, right on the Atlantic coast. We are an authorized Foil Drive reseller. We provide full after-sales support directly from our store. If you have any questions about the compatibility of your unit, motor, or mast, just give us a call or stop by the shop. We'll help you out with the actual equipment in hand.
▶ Need advice?
GlissEvolution, 2c avenue du Gulfstream, 44380 Pornichet (Loire-Atlantique)
09 62 64 74 77 | WhatsApp: 07 83 28 39 94, Tuesday to Saturday, 10am-1pm / 3pm-7pm
Test center available by appointment
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