Why does it take literally days for an electronic toothbrush to reach full charge but a device with larger battery can become fully charged in a few hours
In: Engineering
All common batteries are characterized by charge current which determines how fast it is possible to charge them without damaging the internal chemistry. This figure depends on the chemistry and specific design of the battery and isn’t really affected by size. The lowest charge current to capacity ratio among common batteries belongs to NiMH that can be charged fully within around 2 hours if maximum rated current is applied.
Another common bottleneck is the charge circuitry. In modern microelectronics, higher currents require much more expensive components compared to higher voltages. If you pair this notion with the low nominal voltage of some types of batteries (1.2V for NiMH for example) that make the batteries current capacity more important in relation to its energy density, you’ll find it results in many products that save costs by implementing a charge circuitry that provides far below the rated maximum charge current for the battery it is charging.
In conclusion – It doesn’t really matter what size of a battery you got, all modern batteries are capable of achieving full charge within a maximum of around 2 hours. What you are witnessing is likely the result of manufacturing cost savings in your device.
One way it could be, but probably is not is that the wattage if the charger is very very low, as this lengthens the life of the battery and they will be able to make it bigger as there won’t need to be as big of a barrier between the positive and negative sides of the battery. The way batteries work is that they almost use the electricity to turn a wheel that takes a ion from one side to another. Then when you use it, those ions go back to the other side and turn that wheel powering your device. As people want higher and higher speeds of charging, producers increase the wattage of the charger. this means they have to make the space that is solid in between both the sides of the battery even bigger to not cause problems when charging.
Please let me know if anything I said was wrong so I can correct it
I’d guess because 1 ) the toothbrush is inductive charging, which is much slower and 2) those larger devices are significantly more expensive, so one way the toothbrush companies cut costs is to use much slower battery technology.
If it takes days to recharge, either your device’s charging system is broken, or the batteries have reached the end of their useful lifetime and need to be replaced. Should only take a couple hours max to fully recharge.
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