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.
- Don’t drain the battery down to levels that make the inverter alarm go off.
- 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.
… can begin in earnest soon!
Finally fitted nice snap-on/off battery terminal clips. Also rigged up wires to run from the terminals forwards toward the front of the bike. So I can attach and read my voltmeter as I pedal – a major motivator when it comes to putting in the time pedaling.
But another motivator is the classic “fear of loss”.
Had a dose of that this evening when I noticed the battery voltage was down at 9.41v. Given my considerable neglect over the summer, it may have been like that for up to two months – and leaving batteries like this so undercharged for extended periods is not a good idea.
Time, and some pedaling, will tell if that inattention will cost a battery. But this evening’s not-too-fast, not-muscle-burning 8km spin brought the volts up to 11.72 (with peaks of 15v while pedaling). Of course, the voltage will ‘settle’ overnight. So dawn will be revelatory.
But, potential battery problems aside, I am now happy (genuinely!) to find that I can soon begin to engage in a bit of pursuit cycling: chasing numbers!
More on that later…
Update 22/09/2012: with no more pedaling or drawing of power since this post, the battery seems to have settled @ 10.20v.
Sorry for the long delay – been away a lot and not had time to invest in the project itself or the website.
I left the grid-powered battery charger trickling juice into the battery for about 48-hours. Battery voltage went up to 12.35 or so. I checked it over the subsequent days and it seemed to hold around the number. Then I got very busy and did quite a bit of travelling… but now, over a month later, the battery voltage has dropped only marginally to 12.27v.
That suggests the issue is NOT with the battery.
So I’m left now to try and figure out whether:
- I just didn’t put in enough pedalling for long enough. After all I had deliberately drained the battery to ‘inverter-cut-off-alarm’ so maybe it was just that more pedalling was needed than I thought (mind you the general belief is that when you can get the input charge up to 14.5 volts the battery is as charged as it can be*).
- there’s something amiss with the rectifiers or something else within the turbike unit itself.
It might take a while before Eirbyte.com are able to visit with their fancy testing gear. So maybe in the coming weeks I’ll drain the battery a small bit (maybe charge a laptop) and then see if I can pedal-recharge it back up to 12.3volts. If it stays there then the issue was a pedalling deficiency 😉
But if it drops then there’s something wrong with the turbike’s electrics.
* But maybe that theory isn’t quite accurate and I just needed to do more pedalling?
In my last post I mentioned I’d peddled for over 40mins and the voltage seemed to be settling about 12.0 – 12.1 volts.
Turns out those voltage readings weren’t reliable. I’d come out every few hours to do a few more turns and the voltage would have dropped by anywhere from 0.2 to 0.5 volts. It took another 45mins of pedaling (during which I finally began to hit 14.5v during intense bursts ) before it became clear that the voltage seems to be settling about 11.9v.
I talked this over with Eirbyte.com and they felt those kinds of numbers hint at there being a problem with the battery. It does not seem to be holding the charges I’m giving it.
To check this out, I intend to charge the battery electronically to be sure I’ve got it maxed. Using grid electricity is not something I wanted to do in this project, but this seems to be the only way to make sure I’ve recharged the battery to full capacity. Then I’ll see what voltage it holds.
If it’s not at least 12v then I’m back to the shop to get money back and (hopefully!) find a better battery elsewhere. Because no one deserves €115 of my money for a battery that doesn’t work after just one complete discharge.
… the real learning!
The battery in my old Apple PowerBook (PowerPC) doesn’t hold a charge for longer than maybe 10 or 15mins. So I’m pretty much reliant on an external source of electricity. It’s not the biggest power drain in my office but at 65w (max), and running for hours at a time, it is definitely the biggest consumer.
So how long can I feed it from the turbike-charged battery?
Well, today I ran the computer almost non-stop for 11 hours. For perhaps 5 hours of that time I was also running my 11w daylight-mimicking desklamp. After 11 hours the inverter alarm sounded meaning it was time to pull the plugs to prevent over-draining the battery. The voltmeter showed 11.3v left in it.
So I took the battery out to the garage, hooked it up and started pedaling. The going was tough (the resistance is heavy!) and after 40mins of on-and-0ff pedaling the battery voltage now seems to be hovering about 12.05 – 12.10v.
At no point during that pedaling did I get the volts beyond 13.3v. So all the signs suggest there’s a good bit of pedaling left to do yet! It will be interesting to see how much longer before I hit 14.5v (the suggested point to stop pedaling in order to prevent over-charging).
It’s not my plan to ever discharge the battery this much again. So maybe 4-5 hours would be the max I’d draw out of it on any one day (less when I get a new laptop that charges its own battery while drawing juice). Hopefully that means it could be recharged with 15-20mins of cycling. But only time and experience will tell.
I’m still very new to all this volt-monitoring and stationary-bike exercising, so all I can be sure of right now is that
- mountain bikes are ridiculous machines to try to cycle efficiently on
- the sooner I get my racer installed, the better
- long-term I think I’ll augment this system with photo-voltaic panels
- the pedaling in one position, for extended periods, with a constant pedal rate against a steady resistance could make me very good at time trials (watch out Fabian Cancellara!)
The Turbike is finally up and running in my home (well, my garage actually!). Early days yet and there’s still lots to be done with it… but it is producing power and I’ve successfully run my computer and desk lamp from the battery for at least 6 hours in one go.
Not sure how long the battery will be able to run my office for in one go… but over the coming weeks I hope to test it out and let you know about it. As part of that testing I’ll also keep an eye on how much pedaling is needed to get the battery charged up again.
But initial impressions (after that 6 hour draining, and running 2 laptops for 3:30 one evening) suggest that maybe 20 to 30mins pedaling at a steady and sustainable rate does that recharging quite nicely. This means a daily stint of pedaling might be needed.
Of course if my laptop battery would actually keep a charge… well, things would be much easier. But maybe I’ll be able to afford one soon 🙂