Recharging my electric toothbrush's battery

Discussion in 'General Electronics Chat' started by Cretin, Mar 13, 2014.

  1. Cretin

    Thread Starter Member

    Dec 13, 2012
    Hey all,

    My philips sonicare toothbrush's battery is dead. I don't have the charger, and am a student in electrical eng (2nd year) so I'm familiar with soldering and identifying positive/neg leads (basic electrical know how)

    So take a look at the battery slot below and let me know if the areas I've identified are the positive/negative leads for the toothbrush battery.


    If they are, then could i just look up the voltage capacity of the battery (and the type of battery as well), and simply hook up a power supply set to the required battery voltage, connect the leads to the battery on the points outlined in red above, and just monitor voltage while it charges the battery anew?
  2. THE_RB

    AAC Fanatic!

    Feb 11, 2008
    Without the charger you do not know what the voltage is or what polarity it is.

    I've pulled apart a few electric toothbrushes and normally they are 1.5v or 3v (one AA, or two AAA in series).

    You should try to measure the polarity. If the battery has a tiny bit of sharge remaining you might get a reading on those terminals with a voltmeter.

    Also keep in mind that the NiCd or NiMH battery inside that toothbrush will now be useless if it was left discharged for any length of time.
  3. spinnaker

    AAC Fanatic!

    Oct 29, 2009
    I think it is simply time for a new toothbrush. Somethings just aren't worth the hassle.
    PackratKing likes this.
  4. wayneh


    Sep 9, 2010
    Yes and no. Yes you could roll your own charger. But charging to a voltage, while OK for lead acid, is not a good strategy for other chemistries. A constant current trickle at 0.1C might be better, assuming you can find out what C is for your battery.
  5. GopherT

    AAC Fanatic!

    Nov 23, 2012
    Why not look at other options first. I don't like seeing inexperienced people making things that plug into the wall and become fire hazards over time.

    Try this for $12

    eBay charger
  6. Cretin

    Thread Starter Member

    Dec 13, 2012
    Point taken, but it does not seem all that complicated, I'd really like to give it a try!
  7. spinnaker

    AAC Fanatic!

    Oct 29, 2009
    Gopher has an excellent point. Nicads are notoriously a fire hazard. Just ask Boeing and those are some pretty smart cookies.

    And not to mention a shock hazard in a bathroom no less..

    As a very wise man once said "Penny wise and pound foolish".
  8. Gdrumm

    Distinguished Member

    Aug 29, 2008
    Disaaasembly is the only way I know to discover what you are dealing with.
    That said, you'll probably destroy the seals, and etc. when you do it.

    Just spring for a new toothbrush, and tear that one down for fun.

    You might find a suitable (same) charger on ebay as well, someone else perhaps with a dead battery in their unit trying to sell the charger.
  9. LarryHagel88

    New Member

    Oct 22, 2014
    To avoid further damage to your electric toothbrush, it is best to buy a new one. Soldering the device may cause more problems and may not solve the issue. If you do not have the money to buy the electric toothbrush, then you may use the regular toothbrush for the meantime.
  10. MrChips


    Oct 2, 2009
    This thread is seven months old and the OP has probably found a way to keep his teeth clean in the meantime.