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Monday
Mar262012

CR2450 Coin Cell Charger

This project was mainly a way for me to learn Altium Designer. It started out with me just messing around, but slowly a nice looking board started to emerge. So, I sent the design off to Gold Phoenix and got back 90 boards. It’s a charger for a single CR2450 (LIR2450 to be exact) coin cell. CR normally applies to primary cells (non-rechargeable). I’m guessing LIR stands for Lithium Ion Rechargeable. I bought a few of these cells from SparkFun a while back, but never really used them because I didn’t have a convenient way to charge them. Sparkfun sells a single-cell lithium charger based of the MAX1555 IC, but that chip has been hard to source lately. Regardless, its charging current is too high for this 110 mAH cell, and their board requires another daughterboard to hold the coin cell.

SchematicThis board is based around the MCP73832, which contains all the logic and active devices to charge a single lithium ion/polymer cell. It has multiple charge modes, including constant current which does the bulk of charging. R3 sets the constant current. I chose a resistance of 20k ohms, to get a constant current of 50 mA; that’s about the max charging current one should charge a 110 mAH battery at.

Purchase

Right now I’m only selling bare-boards, $5 each including shipping in North America. If there’s enough interest, I’ll sell fully populated boards. Email me to purchase one.

Downloads 

 

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Reader Comments (2)

Do you still have boards available to sell?

June 24, 2013 | Unregistered CommenterAnthony

Hey Jay, I'm interested in your design for charging the LiPo cells. I'm working on a project that requires simultaneous charge of 2 LIR2450 LiPo cells. Is there any way this design can be modified to accomodate that? I am trying to charge them in parallel via a miniUSB port - I know that charging in series would be ideal but I'm also having trouble designing a switching circuit - so any advice you can give me would be greatly appreciated!

October 11, 2013 | Unregistered CommenterKunal Datta

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