There’s Life In That Beard Trimmer Yet!

You just can’t get a decent beard trimmer these days! At least that’s what [Peter Franck] found when his trusty Panasonic finally expired after a couple of decades and a few replacement batteries. The shaver’s PCB contained a mains-powered NiCd charger which had comprehensively released its magic smoke, and the expensive replacement trimmers he bought simply didn’t cut the mustard.

Many people would have given up in despair, but he persevered, and produced a custom replacement board containing a Maxim DS2710 single-sell NiMH charger, and an AA NiMH cell. It fits perfectly into the space vacated by the previous board, and takes its charge through a micro-USB socket on the edge of the PCB.

It’s interesting to note that NiMH-based projects have in recent years become a comparative rarity on these pages compared to ones using Li-ion or Li-poly cells. This is an inevitable progression on cost, size, and power density grounds, but it’s still worth knowing about projects using the older battery chemistry. He remarks that his razor is now future-proofed, but we’d probably have fitted a USB-C conector before making that assertion. Either way, it’s a neat piece of work that has achieved its aim of making an expired razor useful again. We’ve brought you another razor fix in the past, though a much less sophisticated one.

33 thoughts on “There’s Life In That Beard Trimmer Yet!

  1. Hmm
    I would have upgraded the motor to one of my spare slot car motors.
    That OEM motor is lowest bid for sure.
    On a related note, I tossed my 15 year old Wahl trimmer yesterday.
    Target had a new one.
    Perhaps I’ll retrieve it. (Trash day is Monday.)

  2. FINALLY someone makes a USB-charged shaver!

    I forgot my proprietary-plug charging cord on a trip years ago, but had a small screwdriver with me, so I was able to open up the unit, bodge some wires from a USB-AA charger into the internal cell, and leave it like that long enough to get the job done.

    I meant to swap a USB socket into it when I got home, but it died shortly thereafter anyway, and its replacement takes a normal barrel plug which is easy enough to make a few spare charge leads for, and some of those are USB-to-barrel with a few diodes so their Vf drop matches the stock charger.

    Still not as good as a factory version, though. That’s definitely a purchase consideration next time I’m up for a new one.

    1. I have the same problem with mine… forgot it once….decided to let the beard grow since there was no time for another solution. But yeah, i am really pissed at manufacturers who make devices which could have been charged by USB but are not. They probably know that increases the sales by a few percent from the people who eventually lose the charger.

      1. Before USB mini/micro was a thing and things were charged through it, there was a kind of semi standard 5V ~3mm barrel jack that a lot of stuff seemed to use, PDAs, PSP, some phones. Then really 5V was too much and things wanted 3.3V ish then many phones had 3, then the first larger tablets around had high power demands and the then current current of 500mA at 5V was not great, so they opted for 12V chargers to sock a few watts in. then efficiency improved again and 500mA was enough and new 1000mA USB charging came in also. Anyway it’s been all over the place because of changing demands and changing capabilities.

        1. With current technology we could have barrel-style charging ports that are truly directionless, support arbitrary voltage input, AC or DC, higher currents than anything a USB-C connector could dream of, and no data pins exposing attack surface for hackers….

  3. Now this is a really good, informative, and very instructive piece of work. Congratulations to Peter Franck and Jenny List.

    Due in no small part to the “…when his trusty Panasonic finally expired… hyperlink, this is precisely what a Hackaday article should look like and should be like.

    I’m really getting tired of you Hackaday ‘editors’ and ‘authors’ thinking that re-printing (read that as “copy-and-pasted” from somewhere”) 150 words plus a “…video after the break…” piece of fluff constitutes an “article”.

    I sincerely hope you Hackaday owners are taking good notes.

  4. Lithium scares the crud out of me for wearables, and this is from someone who set a NiMH pack on fire – around his neck! Pro tip – use a fuse, and put the fuse *directly* at the battery pack. :-) Only minor injury, so not a horror story, but another couple seconds and I probably would have had two layers of clothing on fire. I ripped the wires in two when I tore it off and that stopped the short.

  5. Ha! I’ve got a very similar old shaver with the same charging concept (mains powered NiCd charger).
    When it stopped working I first wanted to replace the old battery, remove the internal charging circuit and just charge it from the outside through a barrel jack in place of the C2[1] inlet.
    Later I just used an old external 3,3V SMPS from Buffalo (router) to power the ~1,5 motor directly. The shaver is now on steroids and loud as F***, but it works great.

    [1] https://en.wikipedia.org/wiki/IEC_60320#C1/C2_coupler

        1. Holy sh*t!

          That’s pretty much the same electronics inside as the Panasonic ER205 just with a different brand label and a slightly different PCB shape. I am sure that one is made by Panasonic as well.

          The piggyback PCB will most likely fit into yours, too. It is a very similar board design and shape. At least it would be worth a try.

          If you want to try it send me an email (shaver@kcs.de).
          I will provide you with all the details on how to verify and install the “upgrade”.

  6. I really enjoy Jenny’s style of writing :-)

    I would like to bring forward a word of defence for choosing a mico-USB port: the operation has been carried out already in 2015. At the time the USB-C specification had just recently been released.

  7. Wow, this ia quite a serious replacement. But I get the attachment to a specific trimmer quality.
    I replaced the batteries in mine as well, unfortunately now it is not waterproof anymore because it was not designed to be opened. It’s a shame, since nothing about it appears worn down.
    What amazed me is that even though I bought it in 2014 and it was a current model, the PCB inside said it was designed in 2003. I mean, i guess there is not much more you can do, just charge a battery and turn on a motor.

  8. Yeah, I’m surprised NiMh doesn’t see more love, still pretty handy amount of power in ~2000mAh AAs or ~900mAh AAAs in small enough size. I’m sad it didn’t last longer in power tools, because you can usually bring them back from “dead” if you’re willing to just cycle them properly.

      1. I think it just takes too many cells to get the voltages they want these days. When the competition goes to 18V (power is volts x amps), then to compete you need 15 nicads in series and for duration I would imagine a couple of those in parallel. The same in Lithium is only 5 or 6?

      2. Four times the energy density.

        Four times the replacement rate with batteries that don’t see use and the batteries empty and get destroyed on the shelf (typical use case for consumer cordless tools).

    1. Agreed. And the Eneloops are fantastic. Especially for equipment that will sit for a year or two. The latest AA is average 1950mAh retaining 90% in 1 year of storage. 3 years 80% and 5 years 70%. 4th gen is Rated 2100 charge cycles.

  9. Sometimes i feel like i’m an alien ,alone in the desert. but now that i read Vic’s article ,i know i’m not alone.
    I have exactly the same shaver , and it gave up on me , at least the charging functionality.
    I also bought new shavers to replace this one , every one coming with more useless accesories and carrying cases than the next one ,while lacking basic functionality.
    So I fixed the Panasonic in my own way. A new NiMh baterry was directly connected to the AC power inlet.
    The euro style power lead has 2 pins 19mm apart that fit exactly in a benchtop power supply. Just set it to 600mA current limit and 1.5V

    This went well until my wife tried to charge it directly from 230V mains…..

    1. Amen, brother.

      I kept a trimmer going for another 10 years or so by removing the internal AA NiMh batteries and charging barrel jack from the circuit board and patching in a nice silicone insulated twin conductor cable (from an old Nokia phone charger) which could be driven from my benchtop power supply.

      The mechanicals finally seized up and died a few months ago, but the lovely silicone insulated cord now lives on powering a geiger counter kit with a soviet GM tube.

      The only thing to be done now is seeing if there is a worthy replacement model that will be compatible with the attachments.

  10. I have a Remingtom MB70 trimmer. Long discontinued. The original NiCd “N” cells died so I switched them out for NiMH. That’s one of the really nice things about NiMH, they’re a drop in replacement for NiCd. They hold quite a lot more power, but do take longer to charge. But their lifetime seems to be a lot longer using the ‘gentler’ NiCd charging method rather than trying to charge them faster.

    The trimmer I had before the MB70 used a single AA NiCd. I got hold of a bad cell phone battery (this was wayyyy before smarphones) that used NiMH AA cells and tested them to select the best one to swap into that trimmer. I replaced it with the MB70 when it died.

      1. I’d say that the only time that gets really likely to bite you in the ass is if you replace a 6-700mAh “Super” nicad cell with a “lame cheapy” NiMh that also has capacity down around there, and it’s a sub 4 hour fast charger.

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