Volts/Amps questions

Posted 18th Jan
Hi all.

Please excuse my ignorance. I like to know how things work instead of burying my head ion the sand and assuming the physics fairies will just do their work.

So my bathroom shaving point has two ports: 230v and 115v.
My electric toothbrush charger states "220-240v" but I have always (5 years ish) kept it in the 115v port and I've never had an issue. I believed that 115v output would be less taxing on the charger's components, and only when I have left the toothbrush out of the charger all night do I put it in the 230v socket because I believe it will charge faster (please don't laugh).

I know that phone chargers which output at 2A charge phones faster than those that output at 1A.

My questions: Is there any adverse effect of charging it in the 230v socket?
Higher electricity bill?
Lower component life due to too much power?

Will it even charge faster or have I just been so stupid in thinking that?

Bonus question: Why do pepper mills need 4 batteries when new 2 batteries and 2 dead batteries will still move the mill? Is it to give it more power or is it just so that you can have longer before you need to change the batteries?

Thanks all.
Community Updates


The base that you put your toothbrush into is just a coil, the toothbrush has a coil in it too, this forms a transformer (look on YouTube) dropping the voltage to a level that the toothbrush can take, and then rectifying it and charging the battery.
All that will be controlled by the toothbrush electronics, so you can't overload it so to speak.

I suspect that the 110v outlet might be giving more voltage, but not sure how you'd test that without a multimeter.
As for the pepper mill, the batteries are most likely in parallel as the motor needs more amps aka more energy to turn beefy grinding motor, sometimes you can tell from the electrical connectors, a way to tell might be too just put 2 batteries in and see if it works.
If this stuff interests you, there's no better resource than YouTube
my 110v/240v shaver sockets are different physical sizes, i can plug my 240v toothbrush adapter into the 110 one as the pins are bigger and more widely spaced....
Most chargers / charging bases these days support 100-240V. I haven't seen a 240V only charger in many years.
One way it's sometimes explained is that voltage is pushed while current is pulled.

So a voltage a device can't handle will be pushed onto it and cause problems. While current can only be made available, and making more available than necessary has no adverse effects.

Using a device on the right voltage will do nothing, it's designed for it while using it on the wrong voltage can cause it to fail.

So your 115v socket is lowering component life because they're not designed to work at that voltage. It's also slightly less efficienct to convert to DC so your electricity bill will be (marginally) higher when using the 115v socket, all else being equal.

If your charger is designed to work at 115v then it won't be delivering any more or less power to the toothbrush.

The mill will depend on how the batteries are connected. If they're in series then it's because of it's voltage requirements as that adds battery voltage together. The key bit of info is that battery voltage drops as capacity drains.

So let's say the mill operates in a 3v - 6v range. Fresh batteries run to around 1.5v while nearly empty batteries are around 0.8v. Four batteries go from 6v to 3.2v. But two fresh batteries (1.5V + 1.5V) and two drained batteries (0.8v + 0.8v) is 4.6v so that works fine too.

Even two fresh batteries alone would work, but they wouldn't stay in the mill's working voltage range for long and the mill would stop working when the batteries were only slightly drained, leaving lots of unused capacity in them.

The batteries could also be connected in parallel which would just make them drain more slowly and not add up their voltages, giving more capacity as you state. A combination of the two is also possible.
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