Weather Station Dumps CR2032 Cells, Gains 18650

Despite the fact that we’re rapidly approaching the year 2022, there are still an incredible number of gadgets out there that you’re expected to power with disposable batteries. Sure you can buy rechargeable stand-ins that come in the various shapes and sizes of the traditional alkaline cells, but that’s a stopgap at best. For some, if a new gadget doesn’t feature an internal Li-ion battery and standardized USB charging, it’s a non-starter.

[Danilo Larizza] is one of those people. Bothered by the fact that his Oregon Scientific weather station required a pair of CR2032 coin cells, he set out to replace them with an integrated rechargeable solution. The conversion ending up being easier to implement than he initially expected, and by his calculations, his solution should keep the unit up and running for nearly 40 days before needing to be topped off with a standard USB charger.

Wiring in the new battery.

The first step was determining how much power it actually took to run the weather station. Although the two CR2032 cells were wired in series, and therefore providing a nominal 6 V, he determined through experimentation with a bench power supply that it would run on as little as 3.2 volts. This coincides nicely with the voltage range for a single 18650 cell, and meant he didn’t need to add a boost converter into the mix. He notes the weather station does flash a “Low Battery” warning most of the time now, but that seems a fair price to pay.

Confident in the knowledge that the weather station could happily run with an 18650 cell connected in place of the original CR2032s, all [Danilo] needed to do was figure out a way to charge the battery up from time to time. To that end, he reached for a common TP4056 module. This handy little board is a great match for 18650 cells, and is so cheap that there’s really no excuse not to  have a few of them kicking around your parts bin. You never know when you might need to teach an old gadget new tricks.

34 thoughts on “Weather Station Dumps CR2032 Cells, Gains 18650

  1. I don’t understand the “his solution should keep the unit up and running for nearly 40 days” thing. Two CR2032 cells hold about 470mAh while a 18650 is north of 2300mAh. Was he replacing the CR2032 cells every 5 days? What am I missing?

      1. That still doesn’t compute. Even at the reduced voltage, the 18650 should run it for several times what the pair of coin cells would, and I’m guessing their life would be at least a year.

      2. 4-5x as much though? Can’t be just that.

        I’d be tempted to add a solar panel. If it uses so little current then even in winter a small solar panel should be able to provide enough energy to keep it going.

      1. My thoughts, too. Coin cell batteries can’t provide much current in a short period of time, but they can provide little current over a very long period of time. Wrist watches, calculators, battery-backed RAM (SNES and GB modules; Real-Time Clocks), bicycle computers and digital multimeters come to mind. They last 10 to 30 years, depending on the situation.

  2. My La Crosse outdoor sensor came with a ML2032, recharged by a solar cell. After a year or two that battery failed. A couple of replacements from Amazon failed even sooner. I finally put in an LIR2032, it worked okay during Summer, but Winter sunlight is not enough to power it through the night. But at least that is better than a dead ML2032 which won’t power the sensors even in sunlight.

    1. The circuit as a whole would have a voltage regulator. The IC’s that control and gather the data from the actual sensors need a stable voltage within a certain range. Since neither AC power or Battery power are stable over time, cricuits usually have such a voltage regulator that maintains the voltage stable. Sensors usually need a reference voltage, specially when their outputs are analogue (which nowadays is not usually the case). For this, there are many circuits integrated in the IC’s package that as long they are feed with a high enough voltage, they can provide an output with a constant and very specific voltage.
      Simplest example: zener diode, put a resistor in series and you can vary the voltage over the diode+resistor, and the voltage measured at the diode will remain constant. The zener diode will basically just lower or increase its internal resistance trying to maintain the same voltage drop across its terminals.
      So, in many cases, you only need to supply a high enough voltage.

    2. I had something similar with my La Crosses sensor. It came equipped with rechargeable AAs that would last a couple of years. I thought about installing something different, but nothing quite worked right with the postage-stamp-sized solar cell the thing was equipped with. Finally went ahead and cheeped out with just using regular alkaline AAs, with the knowledge that I’d have to clean up a mess every 720 days.

  3. Electronics n00b question, but will this weather station still measure correctly when the supply voltage is so far off nominal? What sort of circuitry guarantees that the measuring apparatus gets a consistent supply?

  4. “For some, if a new gadget doesn’t feature an internal Li-ion battery and standardized USB charging, it’s a non-starter.”

    And for others, having a built-in Li-ion battery that means you’ve got at most 3 years from the factory to the landfill is a non-starter.

    The built-in Li-ion nonsense is just part of the planned obsolence companies love so much so they can sell you a brand new $300 gadget when a $5 battery needs replacing. At least for the 99% of the population that won’t crack open a device.

    For years, I wanted a controller to use with my iToys, but the only viable option was a steelseries nimbus with it’s Li-Ion battery. There were so many times I put it in a cart but abandoned it. The day support came out for xbox controllers, I ordered an xbox controller which takes AA batteries (and I use rechargables). It is also so much more convenient to swap a set of batteries when they die than to have to recharge the whole device.

    When I bought my gaming console, I picked xbox over ps5 and 99% of the reason is the xbox controller takes AA batteries while the PS5 controller has a built-in lithium ion. The built-in Li-ion is a hard deal-breaker for me.

    1. I’m with you and I think I understand your feelings a bit. I’m a 90s person and went through the Carbon+Zinc/Alkaline/NiCD/NiMH/Li-Ion/LiPO transitions of “batteries” in consumer’s/household electronics. The young people here seem to haven’t, though. They just started discovering these things and are just learning yet. Through PDFs, specs on websites, YT videos etc rather than through personal experience in real life or through the aid of parents or older sisters who knew how batteries react under real life conditions. Thus, they have a rather academic point of view of the matter, rather than the practical, down to earth approach of trial and error. ;) Anyway, they are partially autodidacts, at least, which is a good thing. As long as they stay curious and keep thinking for themselves, there’s hope. Best regards, Joshua

    2. I’ve never had an issue replacing lipos myself, even in devices that are supposedly non-user replaceable. A dead lipo that hasn’t overly swelled sure beats alkaline leakage corrosion damage that eats everything in its path!

    3. Don’t put Energizer or Duracell (Duraleak) alkalines in anything you wish to keep working, they are notorious for leaking electrolyte at end-of-life. There’s a reason TV remotes ship with GP, Sony, or Panasonic – these brands fare much better against leakage. Trouble is, you can’t buy them in stores since Duraleak and Energizer do such a good job of dominating store shelve space – you have to order them online.
      Energizer lithium carbonate batteries don’t leak, but they are expensive.
      Store-brand batteries tend to be Duraleak.

      1. Interesting. I’m in my 50s, and have used Duracell batteries all my life. The only time I ever experienced an issue was when I rediscovered a calculator that I was given some time around 1979. I found it in my mother’s basement in a box of assorted junk last year. It was dead; when I opened it to swap batteries, I saw that the metal connectors were corroded. I cleaned them up a bit, installed a fresh set of batteries, and saw the green LED display come alive again.

  5. I’d rather use one of these..

    They probably last longer than the that weather station itself, if properly stored.
    My father bought some of them over ten years ago, stored them and they still worked after we found them again.

    Especially the 3R12 is a battery someone can be dependent on.
    Okay, the carbon zinc type tends to disintegrate after a while.

    But otherwise, it’s rather environmentally friendly. There chassis made from cardboard, at least , I mean.. :)

    Also.. It’s near 5V, the former TTL voltage and still below 6,3v, the voltage used by tube heaters.

    Here in Germany, the flat 3R13/3LR12 4,5v battery used to be the classic predecessor of the 6LR61 9v battery. And it was more powerful, also. Use two of them in series and you have had a bettery 9v battery, also.

    Too bad the 4,5v battery never got a rechargeable version. The closest thing was a mechanical 3R12 battery adapter that held Mignon batteries/accus.

  6. Wouldn’t using a Lithium Thionyl Chloride (LiSOCI2) Battery (e.g. Xeno XL-060F AA) have been a better choice here? These have low self-discharge, wide temperature range and the AA-format has 10x capacity of a CR2032.
    They can not be recharged and they have a high internal resistance, but that wouldn’t matter for this application.

    1. Thionyl batteries are pretty bad at giving current out quickly and they have a pronounced voltage dip due to the passivation layer on the electrodes that keeps it from self-discharging. If the device isn’t designed for it, it may run into a reboot loop where the MCU keeps resetting because the battery voltage crashes down every time it tries to start.

  7. Hold on: a weather station is supposed to be a set it and forget it type of device: one that is supposed to need very, very little maintenance. Any sort of disposable battery would presumably keep it going for multiple years. To have to actively interact with it monthly is a massive downgrade.

    So if you’re going to hack it to turn the battery rechargeable, it seems almost criminal to not properly finish the hack with a charging circuit hooked up to a solar cell or homemade RTG to give it a competitive length of time between maintenance intervals.

  8. Funny. I was tired of swapping out the CR2032s in my weather station every few months. I soldered in a set of AA alkaline cells about four years ago. It’s still running. Probably need to warm up that soldering iron again soon though.

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