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Foil Drive Lithium-Ion Batteries ExplainedUpdated 11 days ago

This article features information about these batteries and how you can respect them for prolonged efficiency and performance, and what to do if your battery gets wet. 

The 2170 series battery cells we use in the Foil Drive systems feature the highest energy density available while still having the suitable discharge performance requirements. We utilise the best cells we can get our hands on to maximise the power output, run time and performance of the system, whilst completely filling the space available in our electronics box. 

Basic Terminology

- Cells: These are the individual batteries that combined, make up the Foil Drive™ battery.

- Discharge: Every time you use the battery, you are discharging (lowering) it's capacity.

- Cycle: A full charge and then discharge of the battery is considered one cycle.

- SOC: State of Charge.


Life Expectancy

Every battery in existence has a limited useful life span. From the day they are first created, batteries will slowly degrade over time, diminishing their ability to deliver full power output and capacity. This is simply a biproduct of battery chemistry that is unavoidable and part of every battery’s life cycle.

Typically, you can expect to get 1-2 years of good performance out of your Foil Drive™ batteries. It is possible to use these batteries beyond 2 years, depending on many factors such as how you treat the battery, how often you cycle it etc.


The battery chemistry has the ability to charge and discharge for many years past its peak performance, however, the amount of power and punch they can deliver will always diminish over time.

Example: When new, a mobile phone can hold its charge well for 1-2 years. Over time, the performance diminishes, and you'll notice the maximum runtime of the phone is less than it was when new. That same phone can still effectively charge and discharge for years to come, but it's run time is much shorter and often goes flat well before it used to. Just because a battery can be charged to 100%, doesn’t mean its capable of delivering the maximum/necessary power output. The only issue with this analogy is that you cannot feel the power drop of a phone as you are not riding it! The degradation of any battery is more noticeable when you are physically riding a device it is powering, you feel the effects as opposed to seeing the effects.

Usage and Cycling

Every time you charge and then discharge the battery you are putting a “cycle” on the cells. This cycle effectively means the battery chemistry has had to store electrons in the charge phase, then release those electrons when discharged (extremely simplified explanation).

Every time you do this the battery chemistry effectively ages and thus loses a very small amount of overall performance. Over many repeated cycles, this effect builds up cumulatively and the pack becomes less "punchy". This is normal and part of the process of using batteries. This means if you use your battery several times day, your cycle count will be higher than someone who uses it once a week and, you may experience a shorter peak performance time frame.


How To Treat Your Battery With Care

SOC - State of Charge  is the measurement of available energy in the battery at a specific time, referenced as a percentage, put simply, it is the percentage that the battery is charged to. The best way to leave your battery is at a storage state of 35-50% SOC, in order to preserve the battery chemistry for as long as possible. Check out our Battery Checker as a great way to monitor your batteries. Leaving a battery fully charged for long periods of time without use will age the cells and reduce their useful cycle life. Leaving your battery fully depleted also is not recommended, but as a last resort is less harmful than full charge.

Unlike other types of batteries, Lithium-Ion batteries do not have a "memory" as such and do not need to be fully charged and discharged to maintain peak performance or capacity.

Discharge Device: The best way to protect your cells and make sure your batteries peak performance lasts as long as possible is to follow this SOC recommendation. We have a Discharge Device available that will automatically discharge you battery down to the optimal storage state.

Manual Discharge: The alternative is to manually discharge your battery. You can either simply come in from a session with battery charge remaining OR you can run it down while cleaning, simply stand your mast in a large bin full of fresh water. Set your controller to a low throttle setting on cruise control and monitor you motor and battery percentage. This will run down the charge of your battery and is a great way to flush your motor. You can always charge your battery for a short period to bring up to a 35-50% SOC.

When to Discharge: If you have charged the battery for a surf but the conditions change and then you don’t end up using the battery, if you don’t intend to use the pack within the next 3-5 days or so, it is best to discharge the pack. The discharge device allows you to automatically discharge the battery down to a storage state. Leaving it full every so often isn't the worst, just don't make a habit of it!



Temperature: Battery temperature has a huge impact on life span of the cells. Keep your battery stored in the provided Lipo bag in a cool, dry place, away from flammables when not in use. NEVER leave your battery in an environment where it can get hot from external forces. You can purchase a replacement or additional Lipo bag from here

Note: You will need to be logged in to your account to view this product. 

Scenario - One of the worst real word scenarios would be to leave it on the dash of a car in direct sunlight. This could easily destroy the battery chemistry and in extreme scenarios could make the cells catch on fire due to thermal run away. Lithium batteries (like many chemicals) need to be respected and treated with care as they can be very dangerous if misused or mistreated.

If you’re using the Assist PLUS to flat water foil and you notice the battery is warm after use, allow it to cool down to ambient temperature before recharging. This is best practice and cares for your cell’s longevity. If you are using your Foil Drive™ continuously, it is also worth coming down off foil every so often, allowing water to contact the external heat sink on the bottom of the box, and allowing your electronics to cool while in use.

Water: Never allow your battery to become submerged in water in any way. If this ever happens, you must treat the battery with extreme caution as it can start to react with any salt or minerals in the water and internally discharge/short out. 

Familiarise yourself with this article so you are prepared in the event that your battery ever gets wet in the future. 

If want to learn more about how Lithium-Ion batteries work and the science behind why they slowly degrade over time, watch this great video below:

Related Articles - Click to read:
Lithium Battery Use, Care and Storage
 Battery Comparison for Foil Drive Gen1 Systems
 Testing the Voltage of a Foil Drive Battery or Charger

Charging the Foil Drive Batteries

To learn more, check out the other articles on our Help Centre which can be found under the 'Support' tab on the website. 

As always, if you have any questions, please reach out to us at [email protected]


Happy Foil Driving!

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