Why would a toothbrush/toothbrush charger blow, running off an inverter?

[fuss]

Tried to charge my electric toothbrush off a (cheap) inverter and it is now blown. (Braun Professional).

Anyone like to offer an opinion as to why that might be?

I had assumed they functioned as the primary of a transformer and were a wire coil.

No comments on the laziness of using an electric toothbrush. It does mean my teeth get cleaned better.

If you are going to use any sort of electronic AC devices on your boat then you should not install anything other than pure sinewave generators or inverters otherwise you will always be wondering what caused the next AC electronic device failure.

Example......A Braun electric toothbrush on a high quality quasi sine wave inverter will last about 3 days before blowing.

A Braun electric toothbrush will last only if used with pure sinewave generators and inverters. I know that through experience.

(At first I thought it was because it fell on the floor, as is usual on boats , so I bought a new one and this blew too)

 

[pteron]

Sounds like there's a market for more robust Braun chargers

 

[davidpbo]

The power available in the magnetic field is proportional to frequency and coil area - so you can have big coils and low frequency or small coils and higher frequency. They chose the latter to get it to fit into the base of the toothbrush!

Thank you for the additional info. If it is at high frequency with some form of oscillator circuit that explains to me why it may have blown in such a short time on a cheap inverter and why a lot of these chargers blow.

 

[pteron]

I wonder if we could modify these to be more robust? Anyone want to send me a broken one?

 

[Spirit of Glenans]

Any rectification would be in toothbrush not the base. I presume they work with the base being the primary of a transformer and the toothbrush having the secondary coil in its base. I would have thought any spikes would having been smoothed out to some extent by the inefficiencies of the coupling.

I note that there are issues of reliability with these chargers.

Seems right as there is no direct contact between base and brush. It seems to work through induction.

 

[Blueboatman]

You have extended my O level electricery understanding a lot! Ta muchly the lucid explanations in this thread.

The power available in the magnetic field is proportional to frequency and coil area - so you can have big coils and low frequency or small coils and higher frequency. They chose the latter to get it to fit into the base of the toothbrush!

 

[AndrewB]

I wish I'd stumbled across this thread earlier - I've just blown one nearly-new and one brand-new Braun toothbrush charger this way. Not a word in the instructions about their unsuitability with inverters. They were guaranteed for 2 years. Unfortunately I threw the receipts. However so many of us have lost chargers this way that a word with Braun will be in order when I get back.

While I've very occasionally known other equipment not to work properly with an inverter, this is the only time I've had anything actually damaged.

 

[nigelmercier]

Not a word in the instructions about their unsuitability with inverters...

[WARNING - OLD THREAD]

Yes they do, where it says:

230V ~

 

[ShinyShoe]

Got a much simpler solution on my boat. Its a bit old fashioned but doesn't need charged...

 

[alanch]

I know this is an old thread but something similar has happened to me but with charging an Iphone on a cheapo inverter. It worked fine on charging now and then as it was the wifes phone, but when she upgraded and gave me her 5 year old Iphone and I charged it regularly on the boat , it failed. Apple diagnosed a failed battery and gave me a brand new phone. Two weeks later, same again. Apple coughed up again for another new phone and now I charge it on board via a 12v car type socket /USB port and no problems.