Battery 7A Set (2Pcs)

A pair of replacement LIHV batteries for the Duotone Foil Assist and Cruise systems

At a glance

• Pack of 2× high-voltage LIHV batteries for the Duotone Foil Assist system
• Each battery: 7,000mAh, approx. 22.8V, 159.6Wh, approx. 900g
• You must use two batteries at a time – this pack is one complete working set
• Real-world assist time per set: roughly 35–60 minutes, depending on rider and setup
• Designed to sit in the Duotone eHarness battery box (Harness Set not included)
• Airline-compliant capacity (per typical 160Wh limit) for destination trips*
• Optimised for fast charging and long service life with the Duotone Smart Charger

These Duotone Foil Assist Batteries are the original high-performance packs used across the Foil Assist and Cruise ranges. Sold here as a pair, they form one complete working set – exactly what you need to power your Foil Assist mast via the eHarness.
Using high-voltage LIHV cells, they deliver consistent power throughout the discharge, so the assist feels strong and predictable right up until it’s time to swap packs. Each battery is engineered specifically for the Duotone system, with the right balance of capacity, weight and safety for foil use rather than being a generic pack adapted from another sport.

If you already own a Foil Assist set, this 2-piece pack is ideal as:

• A spare set for back-to-back sessions
• Replacement packs for heavily used school / rental systems
• A second set to support family sharing or long days on the water

Key specs

• Type: LIHV (High Voltage Lithium)
• Capacity: 7,000mAh per battery
• Voltage: Approx. 22.8V
• Energy: Approx. 159.6Wh per battery
• Weight: Approx. 900g per battery
• Quantity in this product: 2 batteries (one complete working set)

Designed specifically for:

• Duotone Foil Assist Mast AL & D/LAB
• Duotone Cruise Mast AL
• Used with the dedicated Duotone eHarness + Battery Box and Smart Charger

✅ Please note: The Foil Assist system requires two batteries plugged in together to operate. This 2-piece pack gives you exactly one full set.

Battery runtime & what affects it
Duotone quote a typical assist time of about 45 minutes per set, with real-world usage for most riders falling somewhere between 35 and 60 minutes depending on:

• Rider weight – heavier riders work the system harder
• Board volume – smaller boards require more rider input and can be more power-hungry
• Foil choice – smaller, faster foils ridden at high speed use more energy; larger, more efficient wings at moderate speeds are kinder to the batteries
• Average speed & power level – cruising at mid power is much more efficient than full power everywhere
• Conditions – chop, strong current and repeated stop/start sessions will reduce runtime

As a rough guide using Duotone’s own test scenarios:

• 70kg rider, Midfish 38L + Glide / Free wing, mid power → around 45–55 minutes
• 85kg rider, Midfish 48L, mid power → around 45 minutes
• 100kg rider, Midfish 58L, smaller/faster wing and higher power → around 35–45 minutes

Buying an extra pair of batteries allows you to:

• Run two full sessions in a day by alternating sets
• Keep one set charging while you ride the other
• Cover multiple riders sharing a single Foil Assist system without massive gaps between turns

Charging, longevity & care

These batteries are designed to be used with the Duotone Smart Charger, which manages charge profile and voltage to optimise:

• Charging time – roughly 45 minutes from low charge under typical conditions
• Cell balance and health – helping to maximise usable lifespan

For the best longevity, we’d recommend:

• Avoid storing the batteries fully empty or fully full for long periods – store around 40–60% when not in regular use
• Keep them cool and dry out of direct sunlight when off the water
• Use only the official Duotone Smart Charger and avoid “fast charge hacks”
• Rinse and dry connection points after salty sessions, as you would with any marine electronics
• Treat them well and you can expect many hundreds of cycles of reliable assist.

Airline travel & safety

Each battery is specified at around 159.6Wh, deliberately just under the commonly used 160Wh limit for lithium batteries on many airlines. That means, in principle, these packs are:

• *Carry-on compatible ** with many carriers
• Marked with their Wh rating to support check-in and security checks
• *Always check your airline’s current conditions before flying – some carriers have lower limits or require prior approval, and lithium batteries must almost always travel in cabin luggage, terminals protected, never in the hold.

On the water, safety is supported by the overall Foil Assist system:

• Batteries are carried in the buoyant, quick-release eHarness, not loose on the board
• The folding prop and control logic in the Foil Assist mast cut power when you release the trigger or fall
• Cabling is routed cleanly via supplied cable fasteners to minimise tangles

Who these 2-piece batteries are for

This battery twin pack is ideal for:

• Existing Foil Assist owners wanting a spare set to double session length
• Schools and rental centres running multiple daily sessions and needing fast changeovers
• Families and groups sharing one Foil Assist system so each rider can enjoy a decent session without waiting for a recharge
• Riders planning destination trips who want a second set for long days on the water
• If you’re buying your first Foil Assist set and know you’ll be out for long days, adding this 2-piece pack from the start gives you a much more relaxed experience on trips and busy weekends.

Why it stands out

• Purpose-built for the Duotone Foil Assist rather than generic off-the-shelf packs
• High-voltage LIHV chemistry for strong, consistent power across the whole run
• Travel-aware 159.6Wh rating, making airline trips realistically achievable
• Sold as a pair, so you know you’re getting a complete working set – no guessing or mixing odd batteries

Why buy from The SUP Company
At The SUP Company we’re using these batteries every week in our own Foil Assist demos and test fleets, so we understand how they behave in real UK conditions – cold water, chop, tide and all. When you buy from us we can:

• Help you decide whether one or two sets makes sense for your riding pattern
• Talk honestly about runtime expectations based on your weight, foil and typical conditions
• Support you with tips on storage, care and safe travel with your packs
• Supply the full ecosystem – Foil Assist set, eHarness, Smart Charger, boards and foils – if you’re building a complete setup