The myth of recharging batteries with water: why it doesn't work
Soaking alkaline batteries in water doesn't recharge them: it discharges them. A YouTube myth debunked by physics. The real alternative: NiMH rechargeable batteries.
English · Original discussion in Spanish · Published
Recharging batteries with water: the home trick that actually kills them
A man desperate to avoid buying new batteries submerges two AAAs in a glass of tap water. Ten minutes later he dries them, puts them back in the remote control and, miracle, the device comes back to life. The video has thousands of views on YouTube. Physics, however, has something else to say: water is conductive, and submerging both poles closes a circuit that speeds up the discharge. What the YouTuber doesn't show is that the battery was already half charged or that he swapped batteries during an edit cut.
Popular belief holds that water "reactivates" the internal chemicals of an alkaline battery. The reality is more prosaic: alkaline batteries are not rechargeable by design; trying to "revive" them with water only creates a short circuit that drains them faster. The lower conductivity of pure or mineral water doesn't prevent the parasitic current, as anyone who knows Ohm's law will tell you. After the dip, the residual voltage can light an LED bulb for a couple of minutes, but that's not recharging: it's the last gasp before chemical death.
The real savings are in rechargeables
Against the water myth, the sensible option is nickel-metal hydride (NiMH) rechargeable batteries. With a basic charger and a pack of four, the cost per cycle plummets: a typical rechargeable battery withstands between 500 and 1,000 recharges. Anyone with a TV addict in the house or an emergency flashlight recoups the investment within weeks. The math is simple: a quality alkaline battery costs around €1.50 and lasts about 20 hours in a remote; a rechargeable one, about €3 plus the charger, but multiplies the hours by a thousand. The numbers don't lie.
The debate sparked by the water trick, with defenders appealing to personal experience against technical arguments, illustrates well the resistance to being guided by evidence. But in the end, the laws of thermodynamics and electrochemistry prevail. And here's the unsettling fact: if water really recharged batteries, phone batteries would charge themselves every time it rains.
Related discussions in the forum
A man desperate to avoid buying new batteries submerges two AAAs in a glass of tap water. Ten minutes later he dries them, puts them back in the remote control and, miracle, the device comes back to life. The video has thousands of views on YouTube. Physics, however, has something else to say: water is conductive, and submerging both poles closes a circuit that speeds up the discharge. What the YouTuber doesn't show is that the battery was already half charged or that he swapped batteries during an edit cut.
Popular belief holds that water "reactivates" the internal chemicals of an alkaline battery. The reality is more prosaic: alkaline batteries are not rechargeable by design; trying to "revive" them with water only creates a short circuit that drains them faster. The lower conductivity of pure or mineral water doesn't prevent the parasitic current, as anyone who knows Ohm's law will tell you. After the dip, the residual voltage can light an LED bulb for a couple of minutes, but that's not recharging: it's the last gasp before chemical death.
The real savings are in rechargeables
Against the water myth, the sensible option is nickel-metal hydride (NiMH) rechargeable batteries. With a basic charger and a pack of four, the cost per cycle plummets: a typical rechargeable battery withstands between 500 and 1,000 recharges. Anyone with a TV addict in the house or an emergency flashlight recoups the investment within weeks. The math is simple: a quality alkaline battery costs around €1.50 and lasts about 20 hours in a remote; a rechargeable one, about €3 plus the charger, but multiplies the hours by a thousand. The numbers don't lie.
The debate sparked by the water trick, with defenders appealing to personal experience against technical arguments, illustrates well the resistance to being guided by evidence. But in the end, the laws of thermodynamics and electrochemistry prevail. And here's the unsettling fact: if water really recharged batteries, phone batteries would charge themselves every time it rains.
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Summary of a discussion on Burbuja.info - Foro de economía, actualidad y política., translated from Spanish and reviewed before publication. Read the full discussion (11 replies).
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