Li-Ion battery charger

Discussion in 'The Projects Forum' started by goteks21, Apr 10, 2012.

  1. goteks21

    Thread Starter New Member

    Apr 10, 2012
    4
    0
    Hi I'm currently trying to build a circuit that will let me charge my batteries while using my device and if I unplug the charger the device will use the batteries. I have 4x lc18650 2400mah 3.7v battery for an output of 14.8v.

    more info: my big project is to make my dreamcast a portable game console. I want to use this kit ( http://www.mini-box.com/picoPSU-120-power-kit ) to powerup my device but also to be able to charge my batteries (when playing plugged) or if anyone have a better idea

    any ideas will be appreciated!
     
  2. wayneh

    Expert

    Sep 9, 2010
    12,153
    3,059
    I think most folks recommend charging each cell individually instead of the easy approach of just charging them all in series. Li-ion is nice for high power density, but one of the most temperamental to charge.

    I know you said you already have batteries. Here's another idea. Buy an obsolete laptop with a working charger. You might be able to find one for next to nothing. Get two replacement battery packs for it. They won't be cheap, maybe $20 each. Use the laptop as your charging station for your battery packs. One can charge while you have the other in use.
     
  3. goteks21

    Thread Starter New Member

    Apr 10, 2012
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    Ya yesterday I also came up with that idea and around here everybody thinks their laptop only need a minor repair to bring back to life their ''awesome'' performance machine so they won't let it go under 100-150$...

    anyway I'll keep looking for a dead laptop it's only because I wanted to use the batteries I already had.

    just a little something about a laptop, do they all have a pcb to control the power and the charge of the battery or is it a circuit directly on the main board?
     
  4. wayneh

    Expert

    Sep 9, 2010
    12,153
    3,059
    Ha ha, yes, the place to look is the local electronics recycling center. These folks have already faced reality about the true fate of their prized machines.

    No idea how charging management is accomplished. A LOT of it, maybe everything, is done right in the battery pack itself. But I don't know how to take advantage of that from the outside.
     
  5. goteks21

    Thread Starter New Member

    Apr 10, 2012
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    0
    A friend told me he had a used laptop to give (lucky me) so once I'll open it up I will do a qick check about that. I was asking this because when I open my vaio laptop I saw that it had a small pcb only for the power source. Was it only a protection or something, I don't know I did'nt play to much with it since it's mostly my bro's computer so I could mess with it :p

    anyway as soon as I have my hands on the laptop I'll share my ''discoveries'' :p

    ** by the way, if everything is controlled from inside the battery, by opening it we can simply check on the small pcb inside the battery pack and re-wire it up to our use
     
    Last edited: Apr 11, 2012
  6. IvyK

    New Member

    Apr 7, 2012
    15
    1
    Hi there,
    You can use certain IC's that can do the charging for you. They take care of the overvoltage, undervoltage, thermal problems and they charge the batteries at the correct voltage levels and you can charge batteries in series. If you talking dollars I think they cost around $8 but you have to buy some of the external components. You can take a look at the MAX1737 datasheet for more info. It's probably better to go this route as batteries can be sensitive and charging them incorrectly can reduce their lifespan. Lithium ion batteries can be quite sensitive.

    Hope that helps you,
     
  7. goteks21

    Thread Starter New Member

    Apr 10, 2012
    4
    0
    wow that is awesome! the only thing is that it's surface mount but I can live with that. also MAX gives a lot of free sample and there is one available for this IC. thanks I'll be checking this out!
     
  8. IvyK

    New Member

    Apr 7, 2012
    15
    1
    I didn't know about the free samples thing lol... you learn every day:)
     
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