The risk of electrocution from a battery-operated device in water is conditional: it is extremely low for most small electronics but is not impossible. Electrocution involves a harmful electrical current passing through the body, which requires sufficient voltage to overcome resistance. While the low-voltage direct current (DC) found in common devices is far safer than the alternating current (AC) from wall outlets, certain modern battery technologies and specific environmental conditions dramatically increase the potential for danger.
The Physics of Low-Voltage DC in Water
The severity of an electric shock is determined not by voltage alone, but by the electrical current, measured in amperes. This relationship is governed by Ohm’s Law, which states that current is equal to voltage divided by resistance. For a shock to be fatal, the current must typically exceed 50 to 150 milliamperes (mA).
Water itself, in its pure form, is a poor conductor of electricity. However, the water found in pools, baths, and lakes contains dissolved salts, minerals, and impurities, which create ions that make the water conductive. The human body’s resistance also drops drastically when the skin is wet, falling from as high as 100,000 ohms when dry to as low as 1,000 ohms when submerged. This reduction in resistance means that less voltage is needed to drive a dangerous current through the body.
Most small, common battery devices, such as a phone or a 9-volt radio, operate at a voltage far below the level considered hazardous, which is 50 volts. Furthermore, the power source in a battery provides Direct Current (DC), which is considered three to five times less hazardous than Alternating Current (AC) at the same voltage level. AC is more dangerous because it can cause muscles to contract continuously, making it impossible for a person to let go of the source, while DC tends to cause a single convulsive contraction that often pushes the person away.
Identifying High-Risk Battery Configurations
The danger increases significantly when a battery-operated device uses a high-capacity or high-voltage battery pack. Devices like electric scooters, e-bikes, and high-powered cordless tools often utilize lithium-ion batteries that operate at 48 volts or more, a range where the risk of electrocution becomes a real concern, especially in water. If the protective casing of these larger devices is compromised—due to a crack, impact damage, or exposed wiring—the internal high-voltage circuitry can directly contact the water, creating a potentially lethal current pathway.
A separate hazard arises from the chemistry of modern lithium-ion batteries when submerged. Water can penetrate a damaged battery casing and react with the battery’s highly reactive internal components. This reaction can cause a short circuit, leading to a condition called thermal runaway, where the battery rapidly overheats.
Thermal runaway can generate intense heat, toxic gases, and lead to fire or explosion. Saltwater, due to its higher conductivity, exacerbates this risk by accelerating the short-circuiting process. Even if a high-powered battery does not pose an immediate electrocution threat, the secondary risks of fire and explosion from water exposure require extreme caution.
Essential Safety Practices Near Water
Safety codes recommend keeping non-waterproof electrical equipment at least five to ten feet away from the water’s edge in pool and spa areas. When devices must be near water, they should be specifically rated for water resistance using an Ingress Protection (IP) code, such as IP67, which indicates a device can withstand temporary immersion.
If a battery-operated device falls into the water, the first priority is to remove the power source safely. For a small device, remove the battery immediately. For larger devices like a submerged e-bike or power tool battery, do not attempt to retrieve it by hand or with any metal object, as this could complete a circuit. Instead, use a non-conductive object, such as a wooden pole or fiberglass net handle, to push the device away or retrieve it.
Any electronic device that has been submerged should be treated as potentially damaged and unsafe. Even if a device appears to function after drying, water exposure can cause internal corrosion that leads to short circuits and fire risks. A wet lithium-ion battery, in particular, should be isolated outdoors, away from combustible materials, and inspected by a professional before any attempt is made to reuse or recharge it.