White Wire Voltage - 20+ V ??

[BSA]

After some thought I suspect that it's to do with spark plug gapping, mines gapped according to specifications and the output is around 6volts. The spark plugs don't come gapped properly.

BSA

 

[duivendyk]

The reason the output on the white wire looks so asymmetrical on the scope is probably that the CDI unit presents a load to the generator coil only in the positive output polarity,hence the much higher negative than positive swing at the white wire.Hook a negative going rectifier,single diode connected to a shunt RC load to ground & see what happens (10 microfarad plus and play around with different R's.Watch out for correct polarity on electrolytic or tantalum cap.

 

[duivendyk]

Do you mean Li-Ion battery,or a Nmh battery ?,Limh does not exist.40 mA is a pretty small charge current.It would take 50 charging hours to charge a 2Ah battery.

 

[Flapdoodle]

Do you mean Li-Ion battery,or a Nmh battery ?,Limh does not exist.40 mA is a pretty small charge current.It would take 50 charging hours to charge a 2Ah battery.

LiMH batteries DO exist. Mine came from a sick IBM battery pack. (the computer chip inside the pack went bad)

Look at the bottom of this:
http://74.125.45.104/search?q=cache:ezI0C_OKx5QJ:www-sgc.colorado.edu/symposium_archive/2005/docs/112.doc+%22lithium+metal+hydride%22+battery&hl=en&ct=clnk&cd=7&gl=us

Or Google lithium metal hydride battery

You are correct that trickle charging any battery takes quite some time. However, the amount of time the lights are on is very small compared to my daytime riding.

 

[duivendyk]

Thanks for the battery info,apparently the Prius hybrid car uses these.I had thought they used NimH batteries.Was surprized that so far I had a hard time finding much useful info on them on line. l Your negative polarity charging circuit might work better and is simpler than the fullwave rectifier circuits,especially when you are dealing with an asymmetrical input unless you ac couple it somehow.I'm interested to find out if you can do some serious charging with this setup.Would like to know for instance what RC load it can stand before the engine gives up the ghost and what the dc output is then.Something around 10/20 Ohm with 500+ MF across it would be interesting to try out.I don't have a HT engine so have to talk curious experimenters into giving this a shot.The aim is to get an idea what charge current&battery voltages are practical.Then I should be able to come up with a (hopefully) simple charging circuit design including needed battery overcharge protection.

 

[Hot Dog Piggy Tails]

If I have a 10 or twenty ohmer and a 500u farrad ill check it out. 6volt motorcycle batteries are only 7 dollars here and are 3.5 ahours

 

[Flapdoodle]

Would like to know for instance what RC load it can stand before the engine gives up the ghost and what the dc output is then.Something around 10/20 Ohm with 500+ MF across it would be interesting to try out.

10 ohms is WAY too heavy a load. Don't try it! (14.2/10=1.42 amps, X 14.2=20.16 watts).

If I believe the advertised spec of 3.5 watts, then 3.5/14.2=.246 amps. At 3.5 watts 58 ohms would be max load.

Incidentally, when you measure the ohms on an incandescent light figure 10 times that for the on resistance. When the filament is hot the resistance rises dramatically. Use this to calculate the surge current when turning the light on.

I made a few more pics...

Finished headlight, ~7/8 X 1"


Headlight on


Battery pack attached to roof of "trunk". The crescent shape shown at the top houses the 4 LEDs (in series) for the taillights.

 

[duivendyk]

Thanks a lot for giving this a try,on second thoughts,with not really knowing the output voltage a 25 Ohm load might be a tad on the ambitious side to start out with.Anyway when pushing the envelope,you don't know you've had enough until you have had too much,but you can scale back in any case.

 

[Flapdoodle]

I thought I should explain how I arrived at the circuit I am using. These batteries are very sensitive to over charging. In the original IBM battery pack for a laptop, it has a computer chip that senses the charge current, voltage, and temperature of the batteries. Way overkill for a bicycle. I know from experience that 40 ma (max) long-term will not harm my battery pack, so that was the target for a fully charged condition.

When the battery is low, and/or the lights are on, the current across my 120 ohm resistor can go to .12 amps. More than sufficient for my needs.

I had previously rejected zener shunt type regulation, and a LDO (low drop out) IC (integrated circuit) type regulator because they both use considerable power to operate, and with only 3.5 watts to play with, a simple but carefully chosen resistor value was the easy way to go. The simplest things work the best.

There is no capacitor in my completed circuit; the battery does not care if it is only half wave rectification, and smooths it to prevent headlight flicker at idle.

Sorry, I did not mean to get long winded, and have no desire to become the Motoredbike forum's electrical guru.

-Flap-

 

[Hot Dog Piggy Tails]

Yeah 10 oHms is nearly a short. Good math. I cant remember the Capcitive discharge equation in an rc. My set up was done with 4 d's a pair of series aiding 2 series strings in parallel.I have 3 volt LEDs 10mm. Biggest one I could find. Wow its been 6 yrs since I got my degree in Electronics but way cool.