LiPo USB charger using the MCP73831

Paul Asselin has written a description of his design of a USB Lithium Polymer battery charger.

I wanted to build a cheap USB LiPo charger and didn’t like the unavailability nor the price of the Maxim’s MAX1555. Searching for something better, I stumbled upon the Microchip MCP73831. It is still way too expensive in single quantities but there ain’t too many options.

The board is intentionally small and has a status LED. There really isn’t much more to it, it’s a single purpose device and just does the job. It is proudly Open Source Hardware.

Part 1 of the article (mentioned in a previous post) describes his concept using the MAX1555. The final design using the MCP73831, including schematic and board files, is found in Part 2.

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  1. This is for single cell only. I wonder if there is an option for multiple cell LiPo commonly used by the R/C community. Of course it has to include automated cell balancing while charging.

    1. Thanks! But those can only go up to 2 cells in a single rail DC power supply. R/C community would have cells going from one to probably 8 cells in a pack.
      Not to forget the importance of cell balancing to guarantee the battery packs’ lifetime. I couldn’t find any of those with this important and critical feature.

  2. I’d love to see some LiFePO4 charger board, the Microchip charger for that is in DFN-10 only and quite hard to use.

  3. Expensive? Maxim says these chips are $0.85 @ 1k, and Mouser sells them for $1.42 in single quantities. Compared to $7 boost regulator IC chips, these are not expensive. Was the author comparing their price to passives?

  4. There are four versions of this chip based on their output voltage, from 4.20 to 4.50 Vdc. What would be the good one for use with common cellphone batteries?

  5. Researching ways to efficiently run 10 RGB LEDS for 8 hours at a time. They are 880mA when they are all on at full brightness. But, we do not run them at high brightness all the time and the are pulsing them at a rate undetectable by the human eye. Anyone have suggestions on the best IC to help with our power consumption? We need a small light weight Li-Poly.

    1. You might get more attention for your 10 RGB LED question if you add it as a forum topic.
      Meanwhile, did you try arranging some of the LEDs in series to cut down on the total current? The current-limiting resistors just waste energy as wattage (heat), so it’s better to have as little voltage as possible across the resistors. Stacking LEDs can help. You might need to boost the voltage, though.
      I think you’d have a minimum of 3 strings of LEDs, one each for Red, Green, and Blue.
      Maxim and other companies have chips that control the current, rather than the voltage, and thus you can skip the current limiting resistors. There is still a tiny current-sensing resistor for such chips, but they are usually very low wattage, and thus not a waste of battery power.

  6. I’m running a 12v LED strip with a 555 IC in a simple toggle switch circuit.
    Using a 1000 mA LiPo, We are getting 12 – 14 hours of constant light.

  7. is out of service. Does anyone have a link to a cached or moved version of Paul’s work?

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