Battery options

[guest1130]

So, as my bike is slowly starting to look like a bike, I'm at the point where I need to start thinking about electronics. As many of you know, my build is about minimalisation and the same theme goes with the electronics (well.. sorta anyways..). I've planned my electronics as follows:

- No electric start
- LED turn signals
- LED rear- / brake- / registryplatelight
- LED parking light
- LED instrumenpanel lights
- HID / Xenon Lo/Hi-beam
- Only one of the original horns will be used (beep)

As LED lights have a far less wattage compared to filament bulbs of the same intensity, the size of the battery needed will be minimal. I have cocidered running this bike with a capacitor, but feel like "charging" the caps before each startup would be too much of a PITA for a daily driven bike.

So I need a small battery, the exact rating is not yet clear but I know it's definately way below the standard one. I've looked into LiFePO4-batteries (also known as A123 batteries) since it's possible to make your own battery using several cells (http://www.youtube.com/watch?v=UTDctiyUa9E <-- a video of creating one of these suckers). However, there seems to be some tampering required to make this battery work with the stock charging system, a quote from ffjmoore@dotheton.com:

I have been doing a ton of research on those batteries. They will run your bike fine. The problem with them is the charging system on your bike was not built for that style of battery. I have not tested it out yet but from what i have learned the battery will last longer if charged within its operating limits and balance the charge between batteries. To do this you just need a circuit board that limits the max and min voltage as well as balances the charge to the batteries. Its called a BMS.

So, anyone have any experience on making or using one of these LiFePO4 batteries? Also If anyone has any other tiny battery options, feel free to share!

[guest7]

Interesting, but aren't there low amp 12v batteries that size already? Look at scooter batteries and you'll see what I mean.

What ampere (A-h) is the homemade battery?

GC

[guest1130]

For example, the A123 26650 battery has a nominal voltage of 3,3V and a nominal capacity of 2,3Ah. So I could use 4 of these to make a 13,2V 2,3Ah battery.

The thing with these is that LiFePO4 does seem to have many advantages over conventional lead-acid batteries (check: http://en.wikipedia.org/wiki/Lithium_iron_phosphate_battery), fairly low cost and long lifespan to name a few.

[guest7]

Interesting stuff and I too aim to fit a small battery to my caff racer, but I'm happy to sidestep all the charging issues and fit a lead-acid YB4 (i.e. 4Ah) that sells for less than £20.

As for the other options, I thought the XBR could be kicked over with a dead capacitor, or was I mistaken? I bought a bike-specific capacitor (Batpac?) a few years ago and to my shame promptly lost it somewhere between my house and garage before I could fit it 

Thanks for posting the links

GC

[Andy M]

Have you got the full driver circuit for the LED indicators? No point having low-heat, low-energy, all-light LED's at the ends of the stalks and a dirty great resistor turning energy into heat somewhere else.

Andy

[guest1130]

Have you got the full driver circuit for the LED indicators? No point having low-heat, low-energy, all-light LED's at the ends of the stalks and a dirty great resistor turning energy into heat somewhere else.

Andy

I'm not sure what "stalks" means but I suppose it's irrelevant . To answer your question: I prefer to replace filament bulbs with LED's when ever possible. They are much more responsive, have a ton of variety in colors, have way better intensity than bulbs and have a much longer lifespan. And yes, you are correct, the resistor (which aren't all that bulky to me) is required to make the LEDs work but they still take way less amperes to run.

EDIT:...and it seems I didn't read your post thoroughly, as you were referring to the bulky indicator resistors and not my instrument lights - I apologize. - No I don't have the full driver circuit for the indicators but just resistors for now. I was under the impression, that the LED blinkers might work fine with a correct electronic relay without the resistors?