Pedalling… to save a battery?

A few weeks back it looked like my battery was kaput – no longer able to hold a charge. For instance that 10.20v charge of mid Sept dropped way back to 9.6 within two days. Not a good sign.

Eirbyte suggested taking the battery to a garage and have them charge it for a few days. Because maybe some high amp input might help. So I figured well why not see if I can produce a few high amp bursts myself and see what happens (and if it didn’t then I’d take it to the garage)?

So in recent weeks I’ve found a few spare half hours and done a few 5km spins.*

The first one was the easiest – thanks to the resistance being low. During it I managed to hit a peak of 17.5 volts while pedalling 23-25km/h (for maybe 10-15 seconds). The end of that run saw the battery charged up to 11.2v before gradually dropping back to 10.7 over a week.

Another 5km cycle ten days ago (during which I managed a couple of 16.5v bursts – 17.5 was just not possible) topped it up to 11.75 – and the perhaps reassuring news is that this morning the voltmeter shows the battery still have 11.15v in it. That seems better.

Of course I may be engaging in some futile cycling here. This might not work. But at least I’m getting a bit fitter while learning what sort of voltage can be put out at a given speed.

I’ll give it a few more 5km cycles and see if the charge can be brought back up to – and stays – anywhere near the original 12.3v it had when I bought it. If not, then I’ll try the garage.

But two things I’ve learned from this.

  1. Don’t drain the battery down to levels that make the inverter alarm go off.
  2. Don’t leave a battery at a low-charge level for any length of time.

Oh… and now that I’m getting into the numbers… it’d be handy to have the gadgets to measure my amp / watt output. So I can compare my pedaling with that David Butcher (interesting project and, yes, I’ll probably build one of them too!).

* Before you pour ridicule on that rate of pedaling, bear in mind that a) I am dreadfully unfit and b) there is amazing resistance in this yoke! Getting anywhere near 25km/h is quite a feat. Far more realistic to keep around 12-13km/h and work up to short sprints every so often to hit those higher voltages.

Leave a Reply