Saturday, December 17, 2016

Breadboard and perfboard diagrams of an MCP73831 based Li-Ion, Li-Polymer battery charger

One of my ongoing projects is a very low-power electronics device that supposedly runs on a single-cell Li-Ion or Li-Polymer battery for a very long time, hopefully many-many months. In my idea, the battery actually could be a rechargeable one, e.g. LIR2032 or LIR2450 button cell, and I might also be able to recharge them during these months from a small solar panel, so ideally it runs "forever" with a single battery.

I looked for charger circuits and found out there are many incredibly cheap single-chip solutions available. For some reason I do not remember any more, I picked the MCP73831 chip, which is a very small, single-cell Li-Ion, Li-Polymer battery charger IC.

To be able to experiment with the chip, I just took the typical application schematics from the specification and created breadboard and perfboard diagrams. In this post I just want to share these diagrams as they maybe useful for others as well.

Please note that this circuit has no low voltage protection. On one hand, it is very practical as you can use it to restore over-discharged batteries. On the other hand, you should be careful with such batteries. Please read this blog post about recharging over-discharged LiPo batteries.

This chip is coming in a SOT23-5 package, so it is actually too small for prototyping; first of all, it must be converted to DIP format using a SOT23 to DIP adapter board. I used a DIP10 one, because that was at home, but there are other, smaller variants (less legs) as well.

The diagrams are slightly modified. First of all, I replaced the 2K resistor with a 10K one, so it has 100mA output instead of 500mA. I also added one more LED indicating incoming power. So, the green LED is always on, the red LED indicates the chargring status.

  • Blinking: no battery / battery fault
  • On: battery is being charged
  • Off: battery is fully charged 

I created Fritzing diagrams, and also a DIY Layour Creator one for the perfboard diagram as I find it nicer than the Fritzing one:

MCP73831 LiPo charger Fritzing diagram

MCP73831 LiPo charger perfboard diagram

And finally, the realization. Two remarks: 1. I added some more connectors to the perfboard to make it more useful 2. A single-sided perfboard would be sufficient, and would look nicer, but I had only the double-sided at home

MCP73831  LiPo charger breadboard

MCP73831  LiPo charger perfboard



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