What’s Known, What’s Speculation, and What Riders Should Learn

A short video circulating on Instagram appears to show a SiFly eFoil battery burning after a water-ingress incident. The clip has triggered heated debate in the comments—some of it informed, some of it brand-driven. This article summarizes what’s currently being claimed, explains what might have happened technically, and outlines practical safety steps for riders and schools. As far we know this is the first incident of a burning sifly battery. (We know about a few other faulty not working sifly batteries – mostly caused by users and deep discharge and longterm storing in winter. )

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Ein Beitrag geteilt von Stephan du Plessis (@steph_dplessis)

What’s known so far (based on the circulating reports)

According to the information currently being shared alongside the video:

• The incident reportedly happened in the United States.
• The battery was allegedly brand new and filled with water immediately after use (or after first exposure).
• The suspected causes being discussed include:
  • a manufacturing issue (e.g., missing/failed seal),
  • a faulty pressure relief / vent component,
  • or transport damage that compromised the battery housing.
• The battery was reportedly brought to the beach, covered with sand, and later burned out.
• SiFly stated in a comment that they are investigating and that further details will be shared once confirmed.

At this stage, these points should be treated as unverified incident claims unless and until SiFly (or an independent authority) publishes a formal incident report.

This is what Stephan du Plessis wrote to the incident.

„Close call today! ⚠️ Lithium battery incident, some raw clips. We tested one of our brand new eFoils for the first time and we noticed something wrong immediately, the battery got flooded with salt water internally due to what we believe might be a factor fault. Very soon after we could see smoke coming out of the battery. We know it’s almost impossible to extinguish a lithium battery fire. Luckily we rushed it to shore very quickly and got it to the safest place possible (at the time) ensuring no one got hurt or the vessel burnt down. Glad to say no one got hurt!“

Why “water ingress” matters with eFoil batteries

Lithium-ion packs are high-energy systems. When a pack takes on water—especially saltwater— risk increases because moisture can:

• create short circuits or leakage paths,
• accelerate corrosion on contacts and internal components,
• lead to connector heating and charging failures,
• and, in some failure modes, contribute to thermal runaway (self-heating that can escalate into fire).
• Disables the BMS (Battery Management System) and its safety features

SiFly’s own user documentation emphasizes keeping connectors free of water/salt and warns that salt deposits can interfere with charging and overheat electrical contacts—potentially leading to damage or even fires at contacts/cables. The Battery Compartement from the Sifly EPP Boards like from the Sifly Rider are not waterproof. Sifly inofficial even suggest to have some water inside to have better cooling on very hot days – because the EPP-Foam isolates the heat a lot. Therefore you have to make sure, that the Battery Connector ZC6 seal is with silicone and not damaged. IP68 only means the connection is waterproof 30 minutes when 1,5 meters below the water surface.

Plausible causes being discussed

If the battery truly took on water right away and later burned, an investigation would usually consider several categories:

1) Seal / enclosure failure (manufacturing or assembly)

A missing gasket, incorrect assembly torque, or material defect can allow leakage. If water enters the enclosure, internal corrosion or shorting can begin immediately.

2) Vent / pressure relief component issues

battery systems at this sices incorporate vents or pressure relief features to manage abnormal internal pressure. If a vent or its sealing interface is defective or damaged, it can become a path for water ingress.

Tip: You should alway rinse your batteries with fresh water – if salt cristals built up in the over preassure valves it is possible, that they force them open so water can get in over time!

3) Transport or handling damage

Even a “new” pack can be compromised by drops, impacts, or crushing forces in transit. Shipping damage can be subtle (hairline cracks, deformed housings) but still critical.

SiFly’s documentation also notes these batteries are treated as dangerous goods and advises using shipping specialists for transport (reflecting how seriously impact and logistics are taken for high-energy packs).

As seen at the end of the efoil battery buring video – it is not much left so hard to investigate what was the cause.

“They buried it in sand” — a note on emergency response

People sometimes try to smother burning objects with sand, but lithium-ion battery events are primarily driven by internal reactions and can re-ignite. The safest priority is always:

• move people away, avoid smoke,
• call emergency services, and
• prevent spread to other combustibles.

Fire guidance commonly emphasizes cooling as the key objective with lithium-ion fires; water is widely cited as effective for cooling and controlling spread for lithium-ion incidents.

In this case it was dangerous to carry the battery to the shore (but they have done it on a separate SUP Board) – better to just dump it into the sea (water) of course it is not environmental friendly. Exploding battery parts can cause serious injuries and fire in a distance.

The bigger point: this isn’t only about one brand

In the Instagram comments, brand ambassadors and owners are arguing about “whose battery is safer.” The uncomfortable reality is:

• Incidents have occurred across the wider lithium-ion world, and eFoils are a harsh use case: water exposure, salt, vibration, impacts, and frequent handling.
• Many battery failures are not “random explosions,” but the result of damage, contamination, improper charging, overheating, or misuse—sometimes combined with an underlying defect.

This is why manufacturer guidance generally stresses supervised charging, correct chargers, and meticulous connector hygiene—especially in marine environments.

Safety checklist for riders and schools (actionable, brand-agnostic)

Before riding

• Inspect battery housing for cracks, deformation, loose ports, or compromised seals.
• Check connectors for corrosion, sand, or salt residue.
• never drop your battery

After riding (especially saltwater)

• Rinse/clean per manufacturer guidance and ensure connectors are clean and fully dry before charging. SiFly explicitly warns to ensure no dried salt/water/debris on contacts and to avoid charging with damaged connectors.

Charging

• Charge only with the manufacturer-supplied charger and under supervision in a dry, cool, ventilated area.
• If there’s any sign of water ingress, corrosion, or connector heat: do not charge.

If a battery floods or you suspect water inside

• Treat it as unsafe until assessed by the manufacturer/service channel.
• Isolate it away from combustibles, in a well-ventilated area, and follow manufacturer instructions for handling/disposal/transport.
• Do not store or transport a unstable battery in your car – call professional services to remove and carry big batteries.

Status and Updates

At the time of writing, the incident appears to be under review based on what’s being shared in the Instagram ecosystem. We will follow this incident and look for status updates.

Update from 06.03.2025
Sifly stated: „Based on what we know, the battery involved was missing its vent plug, a small but critical component that seals the battery enclosure and keeps water out. When the battery entered the water without this plug installed, water was able to enter the housing. This caused an internal short circuit, heat build-up, and ultimately a fire.“

Here are some tipps to keep your efoil battery safe and healthy