Sunday, May 17, 2009

USB Coin/Button Cell Battery Charger

I have designed many small footprint PIC projects (such as, pocket watches and wristwatches) but I cannot make them really portable. To make them portable, I need small power sources. Of course, Coin Cell battery would be the smallest DC source that I can buy. The problem is that a Lithium button cell provides 3 V. which is not enough to drive my projects. I thought about using DC-DC step-up converter to boost 3 V. to 5 V. However, it's a little bit complex to add DC-DC converter to the projects. Moreover, my projects consume a lot of power as they consist of many LEDs, a button battery will not last for a day. So, I stopped my think at that point.

Just recently, I have found a rechargeable coin cell battery at Sparkfun.com. It provides 3.7 V. at 200mAh. I don't know that my projects will work at 3.7 V. or not. But, I want to give it a try. For portability, I want to charge the battery from my computer's USB port. So, I designed a USB coin cell battery + charger breakout board. Like many simple battery charger, I use MAX 1555 as the controller of the charger.

The schematic:


The single sided PCB (40mm x 30mm):

The LED goes off when the battery is fully charged (but the charger is still charging).
Please note that the schematic/PCB are just the design and I haven't made it yet. The parts are ordered and I will update when I complete the hardware.
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8 comments:

  1. RicardoATBMay 20, 2009 at 12:20 PM

    I didn't know this MAX1555. Great info!

    P.S.: Actually, I'm building a battery charger (AAA or AA) using LM317 as the current limiter.

    Hugs

    ReplyDelete
  2. AnonymousJuly 27, 2009 at 5:00 AM

    hello... hapi blogging... have a nice day! just visiting here....

    ReplyDelete
  3. spcmicroOctober 4, 2009 at 8:17 PM

    Did you ever get this working?

    ReplyDelete
  4. PunkkyNovember 3, 2009 at 1:36 PM

    I just got the parts ready. The experiment will be conducted very soon. Please check back.

    ReplyDelete
  5. Sander KromwijkNovember 12, 2009 at 3:14 AM

    Nice project! Did you get this working?

    I'm also trying to get a charger to work, but I don't know enough about electronics. Do you know any way to adapt this to charge other types of batteries/other voltages?

    ReplyDelete
  6. UnknownJanuary 18, 2010 at 6:39 AM

    Hello how is it going with the project I am making my own little project with a light using 2x 2016 3.6 v coin batteries, and would love a charger my email is jacobsen-eschel.com

    Sincerely

    Eschel Jacobsen

    ReplyDelete
  7. D. GallotNovember 9, 2010 at 8:23 PM

    For really small load, you can use the stepup converter from XP Power.

    http://be.farnell.com/xp-power/ie0305s-h/converter-dc-dc-1w-5v/dp/1436115

    Does not required any external components !

    ReplyDelete
  8. Eteily Technologies India Pvt. LtdJune 3, 2024 at 2:16 PM

    Hello Friends,
    I Read Your blog It have very informative details, it is very useful for me. because I make a project in which use Battery. I also have some details of Lithium ion batteries.
    Battery Manufacturers

    ReplyDelete