Add supercaps to your exercise routine

Many exercise machines generate electricity as you pedal or climb in order to run the on-board electronics. Unfortunately if you stop or even slow down too much the juice will die and your exercise program will reset. Wanting to improve on this gotcha, [Mike] cracked open his exercise bike and added some super capacitors.

On the circuit board he found an ATmega128 was in charge of the user interface. He probed the board a little bit and couldn’t find how it was connected to the power regulators. After some additional snooping he found it has its own SOIC regulator separate from the ones that run the display and peripherals. He takes us through the calculations he made before choosing his parts. What he ended up with is a set of three supercaps in series that add about two minutes of juice before the levels drop and the chip resets. The design of the board helped a lot as the high-load electronics (like the LCD screen) are on a separate power bus than the processor.


  1. djrussell says:

    “Many exercise machines generate electricity as you pedal or climb in order to run the on-board electronics.”

    They do? I sold treadmills, bikes, and ellipticals for a year or so and all of them took batteries to run the display.

  2. Brennan says:

    The treadmills we have at work do indeed reset if you step off them for a bit. Sometimes I’ll come back from refilling my bottle at the drinking fountain and everything has reset. However, I highly doubt it has anything to do with capacitors, because the treadmill is plugged into the wall. I’m sure the reset is just a timer, not an actual brownout.

  3. Mike says:

    Whoa, batteries? I’ve seen bikes you have to plug in, and I thought that was a pretty poor design… Hopefully they lasted for awhile! No backlit displays I imagine.

  4. djrussell says:

    they weren’t as nice as life fitness stuff. mainly nordic track and proform. we rarely had to replace them but they were also usually C or D cells, 2 or 4 of them.

  5. hmm says:

    “Unfortunately if you stop or even slow down too much the juice will die and your exercise program will reset.”

    Never ever had this. Ever.

  6. bogdan says:

    Oh, is this just so you could take longer breaks from your exercises?

    I do have say, I’ve never met any of these machines that didn’t use batteries or got plugged in.

  7. DarkSim says:

    I used to use some exercise bikes at JMU that were physically plugged in. Even then if you step off for more than like, 30 seconds or so, it resets your statistics/session. Not a hard reset like we typically think. Guess they program them to time-out ; and think that the user is done exercising, which is unfortunate when you get really far in one of the pre-programmed scenarios. :(

  8. andres says:

    i’ve seen a few excercise machines powered by the workout. a few ellipticals and rowing machines. blank screen, pedal for a few seconds and *beep*. stop for a few seconds and they turned off.

  9. vonskippy says:

    Hard to see where the cost/effort was worth the measly addition of two minutes.

  10. djrussell says:

    correction to my first comment: the treadmills all plugged in. no batteries. one of the ellipticals plugged in too to run the incline motor.

    i have a H20 rowing machine and the display takes 4 AAs. it automatically turns on when i start rowing. it will reset after maybe 15 sec of stopping. barely enough time to review the workout stats. there are only two wires going to it which i think are for a sensor. no backlight.

  11. Lion XL says:

    “Hard to see where the cost/effort was worth the measly addition of two minutes.”

    Maybe not cost effective, but two minutes should be enough to say answer a call, grab a quick drink, review stats, update a log, list goes on. I dont think this hack was intended to super size the thing, but just give you little more time before it reset itself. and if he is keeping a written log( alot of joggers do..) then this should be more than adequate to jot everything down before the screen blanks…..

  12. Roon says:

    I would love to see someone reprogram a treadmill, I can just imagine a cartoon style incident taking place with the treadmill going faster and faster.

  13. addidis says:

    We are going to be seeing allot of ridiculously low power devices surfacing soon. No power source , think solar , motion harvesting , flex harvesting material (clothes) impact / piezo harvesting (shoes) . These are all budding tech at the moment.

    Coupling the budding tech with existing tech (motion , flex and impact harvesting + induction) will lead to interesting things.

  14. Simonious says:


    I’m very much looking forward to this and the myriad of hacks that utilize it in surprising ways.

  15. Mike says:

    @Roon – lol, I can imagine that…

    @addidis – ditto Simonious; I almost joined one professor’s research on microgenerators for cell phones and the like. Very cool stuff.

  16. Erik Johnson says:

    I’ve seen machines like this – the display was backlit by blue LEDs. It used 2 AA NiCd rechargeable batteries and the machine would charge them as you worked out.

  17. M4CGYV3R says:

    From the headline, I was hoping it shocked you somehow. Just to, ya know…keep you moving.

  18. Dstrcto says:

    Why did he put them in series?

  19. Dstrcto says:

    Oh wait, he didn’t

  20. Dstrcto says:

    You know what? Nevermind. I just read everything again. I am just tired.

  21. strider_mt2k says:

    Jane stop this crazy thing!


  22. Nate says:

    i think you guys meant he wired the caps in parallel as series would lower the holding capacity

  23. Mike says:

    Actually series is correct – the goal was to increase the voltage which could be stored, despite a loss of capacitance (and technically the energy stored is the same, given full voltage, whether series or paralell is used).

  24. Ivan says:

    In series??? That would divide the capacitance to ~ 1/3. Ah, well, maybe these caps wouldn’t stand the generator’s voltage in parallel.

  25. Mark says:

    He put the the three supercaps in series with each other to reduce the capacitance down to 0.83F, but in parallel with the power supply filter caps to increase the overall capacitance.

  26. Mike says:

    FYI, the original article can now be found here:

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