1. Are you ready for the Galaxy S20? Here is everything we know so far!

Is it really that easy? Emergency Charger

Discussion in 'Android Devices' started by JRHPNG, Sep 19, 2011.


    JRHPNG Lurker
    Thread Starter


    Firstly a big hello to everyone here, especially the people that take the time to read this post.

    Like a lot of people with SGS2's I had some issues with the lack of stamina from my phones battery..

    I am currently living and working in PNG so do not have access to any off the shelf chargers... So what I do have access to is power tools and their batteries and I found a Chinese car charger..

    Is it really that simple to make an emergency charger? The car charger accepts 12-24v and the battery is 18v so no issue there.. The car charger brings the volts down to just a shade over 5v.

    Obviously the pic was just testing the current etc but will this work if I streamline the package and make it a little more permanent?

    How many full charges will I get from an 18v / 2.6Ah battery?

    Any help / advice / warnings would be great...

    Cheers! :)

    Attached Files:


  2. d8beat

    d8beat Newbie

    I have no idea but it sure sounds like dangerously bad idea. can't u get 1 from ebay?
  3. bonerp

    bonerp Android Expert

    good way to see how explosive the battery will become
  4. WizGnome

    WizGnome Lurker

    I have been using the same arrangement to charge a range of other 5v USB powered devices & phones for the past couple of years whenever I go on a camping trip away from the car and any other source of power.

    Not sure how many charges you will get, but can't see how it would not work as it is no different to charging from a car socket.
    JRHPNG likes this.
  5. geoffibs

    geoffibs Member

    Yes and no. I use them, but not all are the same so I can't say a definite yes. Do you have any test equipment?

    Load regulation is generally quite bad so I would recommend some checks first.

    Some chargers don't give out a straight DC voltage but have it pulsed. Similar to AC but only on the positive side. unfiltered, unsmoothed and not very stable as far as voltage drift goes. Although it could be ok, the rapid switching could damage the car adaptor and in turn your phone if this gets though.

    Other chargers are intelligent and switch on and off depending on load which may not cause any damage, but not very good at charging.

    For the ones that will work, you will be looking for a constant, smoothed DC voltage on the output side if you or your colleagues have any test gear, ideally look at the waveform on an oscilloscope. If it is intelligent, you may have to play around with the control pin of the charger to get an output.

    Charging a 12-18v battery and using your adapter off that will be fine. Not sure how long it would take to charge though. Should be the same as the car as the adaptor will probably be current regulated to 350-500mA so you should get a fair few charges from a 2.6Ah. 500mA off 2.6Ah would give you five hours taking the full current. If it uses 300mA then you will get just under 9 hours. Probably less taking into account the loss of the adaptor conversion and condition of the battery.
    JRHPNG likes this.

Share This Page