Can an electric hot water bottle with smoke coming from the charging port still be used?
No.
If smoke appears while charging an electric hot water bottle, it must not be used further. Immediately disconnect the power source upon noticing smoke, as this indicates potential circuit burning that could cause a fire. Additionally, promptly dispose of any hot water bottle exhibiting smoke.
Why does an electric hot water bottle smoke?
Electrical issues
Smoke during charging may result from aging circuits or poor socket connections. As a high-power appliance, smoking may occur if the voltage exceeds the device's limit during charging.
Substandard Product Quality
If your home's electrical system is functioning properly yet smoke still appears during charging, and the heating pad is relatively new, the issue likely stems from poor product quality. It is strongly recommended to purchase heating pads only from reputable manufacturers.
What Fluid is Inside an Electric Heating Pad?
A supersaturated sodium acetate solution.
Electric hot water bottles typically contain a supersaturated sodium acetate solution. When a solution's concentration equals its solubility, it is called a saturated solution; when its solubility exceeds its solubility limit, it becomes a supersaturated solution.
This supersaturated solution is unstable. When electricity is applied to heat the metal, even slight vibrations can cause the solute to crystallize into a more stable solid state. This process releases heat, causing the heating pad to warm up.
Is it normal for an electric heating pad to become noticeably bulging after charging?
Expansion may occur.
During charging, especially near completion, the electric heating pad may noticeably swell. This occurs due to thermal expansion and contraction. The pad isn't filled entirely with liquid; it contains some gas. As the liquid heats during charging, the gas expands alongside it, causing the entire pad to bulge.