This Coin Cell Can Move That Train!

[Mike Rigsby] has moved a train with a coin cell. A CR2477 cell to be exact, which is to say one of the slightly more chunky examples, and the train in question isn’t the full size variety but a model railroad surrounding a Christmas tree, but nevertheless, the train moved.

A coin cell on its own will not move a model locomotive designed to run on twelve volts. So [Mark] used a boost converter to turn three volts into twelve. The coin cell has a high internal resistance, though, so first the coin cell was discharged into a couple of supercapacitors which would feed the boost converter. As his supercaps were charging, he meticulously logged the voltage over time, and found that the first one took 18 hours to charge while the second required 51 hours.

This is important and useful data for entrants to our Coin Cell Challenge, several of whom are also going for a supercap approach to provide a one-off power boost. We suspect though that he might have drawn a little more from the cell, had he selected a dedicated supercap charger circuit.


28 thoughts on “This Coin Cell Can Move That Train!

  1. I don’t see what is so great about this. Your just using a boost circuit to do this and maybe a power management etc. Maybe it’s just me sorry I find this a waste of time this coin cell thing. It’s all about boost circuits and that’s about it.

    1. You may think so, but only until you actually try to do something high-power with a coin cell. The internal resistance really makes it somewhat difficult, you can’t get more than 0.1 W out of them even in the best case.

          1. Energizer datasheets for the CR2430 and CR2450 both indicate an internal resistance of approximately 15 ohms when brand new, and increasing exponentially when about halfway discharged (about the same time that the output voltage starts dropping)

            So a maximum instantaneous power delivered of about 1/3 W (with another 1/3W as heat in the battery)

    2. I’m learning a lot about battery tech and caps reading these entries. So for you, an expert in all things, maybe it is a waste of time. But for me, who is always learning, its a very good opportunity to learn new things.

      More coin cell projects. :)

    3. i agree. even a boosted coin cell might be interesting, but using effectively infinite time to charge a supercap which will be discharged in only a few seconds doesn’t turn me on at all. you just basically convert C from tiny to monstrous, and then…why use a coin cell? dealing with its low current capacity is the whole interest for me.

    4. I fully agree with out about this flood of silly boost circuits. But as for the contest, there are plenty of things you actually can do with a coin cell, and we can only hope the judges will have the sense to pick winners for thing that do something *with* a coin cell instad of doing something *in spite of* a coin cell.

      The 555 organ was pretty interesting and a great use for a coin cell. I hope we start seeing more projects in that spirit rather than 1,000 more clones of let’s charge the super-cap.

  2. Boost circuits are cool, but I somewhat agree. Next decimal year, when you run this competition, make coin-cell contest with a subdiivision for those that use a boost ckt not for merre voltage accomodation, but for power accumulation, its own contest.

      1. My camera strobes, (twin setup of broncolor Pulso 3200’s) will discharge 6400W/s of power in about 1 millisecond off of a fairly large capacitor box. So, 6.4 megawatts to play with. A 6.4 megawatt power plant would be enough for 4200 homes. So, my camera flash uses enough power to supply 4200 houses. At least Quora tells me a gigawatt power statin will supply 700,000 homes. Not bad for a $3,000 capacitor box. And fwiw, I’m managed to trip out a 20 amp 120 volt circuit a number of times with my flash set-up.

        The point here is, charging up a capacitor and using it to do is a silly thing to do and I hope the mass of silly things diluting this contest don’t ruin the whole contest, but that’s up to the judges.

  3. Urg. This sounds like a waste of time. I guess you can say I did it, but why? Between the extremely long charging time and the still low total amount of power I don’t see anything practical.

      1. Yes, but this misses the whole point of doing something cool with a coin cell. It’s a waste of time to do and a waste of time to read about. Let’s see some more projects that actually do something cool off the power ability of a coin cell. Ultra-low power MCUs, efficient sensors, RF modules. It’s 2017, there are absolutely amazing devices that use amazingly small amounts of power out there. Do something cool with them. That’s what this contest is all about.

        1. Hm… If you put it that way, you have a point…

          There should be many applications aside from leeching the charge and pumping it into some supercap…

          LoRa sensor nodes for example..

  4. I would have been more impressed if he found a way to move the train slowly, at the rate that the battery can discharge.
    One way could be to charge a much smaller capacitor just enough so that there is energy there to rotate the motor to reach the next comutator position.
    Or just replace the motor with a much smaller one that can run directly off the cell.

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