USB Shaver Charger

06Aug14

TL;DR

I hacked together my own USB shaver charger using a cheap DC-DC converter I bought on eBay, so fewer worries (and things to carry) next time I’m travelling.

USB shaver cable

Background

I use an electric shaver most days, and I travel a fair bit. Usually the battery is enough to get me through a trip, but if I’m away for weeks then I need to recharge.

The charger that came with my shaver (in the UK) is a European type like this:

340 Charger

If I had a US charger, I’d be fine, because most places in Europe have both types. Sadly the reverse isn’t true, so it’s less common to find European sockets in the US.

To make things worse the European shaver plug looks like a Swiss style plug, but actually has larger prongs, so it doesn’t just fit into a multinational adaptor. Here’s the hideous jury rig I had to put together on my most recent trip to get a charge:

Shaver charging hack

That photo has a European shaver charger, a euro to UK adaptor (from my wife’s GHDs), a Swiss World Travel adaptor, and an elastic hair band.

I’ve thought in the past that it would be a good idea if somebody like iGo did shaver tips for their travel chargers, but that hasn’t happened. Of course most smaller devices these days use USB for charging.

USB shavers

They do exist, but they don’t look great. I’ll stick with my Braun.

Why not USB?

It’s a mystery to me why the shaver manufacturers like Braun, Philips etc. haven’t shifted to using 5v for charging and supplying a USB charger. I guess they’re stuck in the same place the mobile phone makers were a decade ago (before the European commission mandated microUSB).

The solution

My shaver charger is 12v at 400mA. I got a MC34063A based DC-DC converter module from eBay for £1.68. It’s claimed to be 78% efficient and can output up to 1.5A (though it’s recommended that it’s only pushed to 800mA).

Crunching the numbers:

12v * 400mA = 4.8W

4.8W output/ 78% efficiency = 6.15W input

6.15W/5V = 1.23A

1.23A is well inside the capabilities of a typical USB travel charger for something like a tablet, and even a more mundane 1A charger is likely to be sufficient – worst case the shaver will charge fractionally slower.

The voltage converter came already set up for 12v, so it was simply a matter of dismembering an existing charger cable, and a spare USB cable, followed by a quick bit of soldering and heat shrinking. The picture at the top of the post shows the finished article (with the coiled shaver cable wrapped around the USB charger cable to keep things tidy).

Improvements

At the moment both cables come out of the same side of the converter, and it would be better if it was just a bump in the wire; and that bump could be more elegant than a lump of heat shrink encased electronics.

I’m probably not going to bother polishing this thing any further myself. It works, and I’m happy with it.

Maybe some enterprising Chinese manufacturer will come up with something properly designed, with variants (or even interchangeable plugs) for different shaver types.



2 Responses to “USB Shaver Charger”

  1. This is exactly the idea I have been searching for as a solution to light backpacking. I have a skin condition which mandates no wet shaving but I am fed up off carrying an extra plug. Could this be adapted so I could plug an existing USB cable into a female USB on the end of a very small shaver cable? Do you have a wiring diagram?

    • Sorry – no wiring diagram. Let’s try some ASCII art:

      USB +5v ---- DC-DCin
      USB gnd ---- DC-DCgnd ---- Shaver_gnd
      .............DC-DCout ---- Shaver_12v

      I’m sure you could adapt it in many ways. One option would be to mount a microUSB socket onto the converter, and then just have the shaver cable/plug coming off that.


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