Coin Cell Battery Charger

[Jay Kickliter] built his own coin cell battery recharger. This won’t work on the vast majority of coin cells as they are manufactured as disposable parts. But there are rechargeable options out there with model numbers that start with LR instead of CR. In this case he tailored the charging circuit around MCP73832 IC and chose components best suited for charging his 110 mAh LR2450. But we believe all of the LR options out there are rated for 3.6V so altering his design for use with different models should be a breeze.

We’ve been unhappy with the use of disposable coin cell batteries for some time. Sure, in a real-time clock where the cell might last 6-8 years this is not very wasteful. But in an Apple TV remote that gets a lot of use, we hate the choice of a disposable battery. All of our less-hip remotes which use AA or AAA have NiMH rechargeables in them and have used the same pair for year and years. So we’re happy to see this charger project come along.

Now the bad news. We looked around and indeed you can find LR2032; a rechargeable replacement for the CR2032. But the capacity rating falls way flat. The model we looked at boasts only 50 mAh while the disposable CR2032 offers something along the lines of 240 mAh. Hopefully this will change as battery tech evolves.

19 thoughts on “Coin Cell Battery Charger

  1. I’m not so sure about disposable lithium cells, but I’ve found that alkaline disposable cells recharge just fine; you just have to limit the current to a bare trickle (20mA or so). This takes many days to recharge, but it does seem to work. I’ve kept my single AA battery in my wall clock going for three or four years now, recharging it over a weekend once every 9 months or so.

  2. Lithium primarary batteries can’t be recharged and if you are unlucky they may even explode when trying to do so. Alkaline primararies can be recharged in a very limited way. Some AA/AAA Alkalines are even sold as rechargeable and there are special chargers for them. This might also work for alkaline button cells (such as LR44).

  3. @Thopter: I don’t know exactly how lithium batteries respond to recharging attempts but they work through a different chemistry than alkalines. This might not allow for reversal of the chemical process through reversal of current.

  4. I burnt my finger once trying to recharge a CR2032 coin cell for my Digital Calipers…. I was able to make the measurement I needed, but now I buy CR2032 by the 100s at Digikey (about 5x the price of RadioShack for Q=100).

    1. As a kid I never had the money for disposable button cells (they were not cheap and easily available back then) so I found I could recharge them slightly to run a bit longer, a practice which stopped when one of them exploded in my hands & face.

  5. Like everyone else said, does anyone actually know if lithium button-cells cannot be recharged? I’ve recharged a fair few alkaline AAs with no trouble, but does the chemistry of a lithium button-cell make this impossible?

    1. I believe the standard lithium button cells cannot be recharged. My logitech solar keyboard uses a rechargeable button cell though along the lines of what’s being mentioned. Works well.

    1. I don’t believe they were. However, to simply run a clock circuit such a battery could last years on its own for 24/7 service. Subtract any time that the computer is running to extend the service life of such a battery even farther.

      I’m not certain, but I’d wager that with the advent of ATX power supplies, the trickle voltage to the mobo that is always on (to monitor for power button activity) might also handle the clock circuit – meaning and even LONGER effective life for CMOS batteries…

    2. old ones were, they had a small NiCad (sometimes in button cell’s tabbed and shrinkwrapped), somtime in the late 90’s they pretty much all went to lithium, and if it was not soldered in or tabbed a good rule was they were just throw away lithium (no charging) but if they were “not replaceable” they were the much more expensive rechargeable.

      1. Sadly, not always true. A company I used to work for speced their CMOS battery at 11yr so they wouldn’t have to charge it or replace it. By the time the final version of the motherboard got to market, so many other things besides the clock had been piggybacked on that too convenient battery that it only lasted 11 months. Had to unsolder the battery and solder in a socket to upgrade those original machines.

  6. Honestly, I don’t know if regular coin cells can be recharged. I always assumed the ones on motherboards we’re either rechargeable, or their consumers drew so little current that they just last a long time.

    I can’t find the report I read, but there was evidence that the man in FL who’s electronic cigarette new up was trying to charge primary cells or didn’t know how to properly charge Li-Ion cells. Did old CMOS run off 3.0V?

  7. If Apple made that remote rechargeable, they’d use a coin battery and epoxy it in so when it wears out you throw away the whole TV. Think of the iPhone, Mac Book Pro, and all the other iJunk. You should be grateful you can replace the battery. What you need to do is a MacGyver on the remote so you have on the back a holder for 2 AA rechargeable batteries which you can replace when worn out.

  8. Interesting note: if you cool it down enough ie -8C with a Peltier cooler and charge at 1mA Vlimit 3.6V for 90 hours it will recharge- eventually.
    The reason why CRxxxx are not generally rechargeable is that the very process that makes them high capacity is also the same one that prevents recharging: the Li metal forms dendrites that short it out at or near full charge.
    Cooling it down and charging at a very low current can work but its not advisable for more than a handful of uses.
    The problems faced by lithium metal rechargeables are similar in that various techniques were tried and failed including the use of a solid ionic electrolyte but this mitigates the problem only in short term.

    Interesting random experiment: the DOA <0.3V cells you sometimes get in bulk packs are faulty due to a mistake in manufacturing and generally the cheaper units use Li-Mg not pure Li as cell voltage is 3.3V when good.
    Someone messed up and failed to put enough electrolyte in them so the Li metal is generally in good shape.

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