HT 6v Charging System w/- ground

[loquin]

Btw

I've modified your circuit a bit - this is what I believe it should be...

The zener diode should be wired across the battery terminals, to limit the voltage at the battery to the zener voltage*. If the resistor is included in the portion that's wired across the battery, you're trying to drop the entire voltage out from the white wire (minus the .6 volt forward diode drop) across the battery terminals...


*I also believe that, in order to provide adequate charging voltage, you should increase the zener to 7.2 volts. (Nominal charging voltage for a 12V system is 14.4 volts... and a 6 volt system should charge at half that)

 

[loquin]

If the zener diode has too much current flowing through it, it can overheat as well, even when wired correctly.

 

[loquin]

Here's sample positive & negative ground schematics. I've included a second approach with each, a slightly more complex circuit, which uses a power transistor to regulate the voltage. In this approach, the resistor and zener diode can be smaller, and less expensive. And, the regulator circuit regulated over a much load range, and input voltage range. Note the zener voltage change in the transistor-based regulator circuit. This is because, in this emitter follower circuit, the forward voltage drop of the transistor has to be taken into account.

 

[sofasurfer]

I wonder why Tinker 1980 (post #4) did not have a problem.
Hey, Tinker. If you're out there, sound off.

 

[loquin]

The larger resistor helps, is it would last much longer before frying. (and, depending upon tolerances, it might last a very long time.) The other issue would be short battery life - putting the entire voltage across the battery will 'cook off' the electrolyte in a much shorter amount of time. Weeks-to-months, rather than years, depending upon the usage pattern.

 

[Tinker1980]

I wonder why Tinker 1980 (post #4) did not have a problem.
Hey, Tinker. If you're out there, sound off.

The charging system worked great, but still didn't have the capacity for my needs, in the end. I rode home one night last week, first time trying to ride home with the charging system... I got about 10-12 minutes before the light went yellow. It didn't completely die out, but it was pretty dim. (About twice as bright as a wally-world LED headlight ) The resistor seemed to get kinda hot, I ended up unplugging the light. I'm not a genius with this stuff and wasn't sure if I was courting the magic smoke by running a 35w light through a 10w resistor with a 5w AC source. (Magic smoke is contained in electronics components, when the smoke escapes the part needs replacing.)

I ended up riding home in near darkness, and since then I have cheated. I put the 55w bulb back in the light, and ran the whole thing with a 12v 7ah SLA. It's amazingly bright, BUT I have to plug it in when I get home.

-Mark

 

[Scotchmo]

Does anyone have any thoughts about using a Power Wheels "Power Patrol" battery for this application? It's a 6 v, 4.5 ah lead acid battery. The physical size seems small enough. Would the 4.5 ah rating, which is higher than the originally mentioned 1.3ah item, suggest that additional charging might be needed? My bike isn't run for more than 45-60 minutes at a time, twice a day. It's also fitted with a std. 6v, 3w generator, which could supply a small amount of additional juice to the white wire source. For the light itself, I'm thinking of using a std. 6v, 15w head lamp from a vintage scooter.
(the battery is eBay # 280340681068 B.I.N. at $15.95 with free shipping)

Ode

I finally got access to a computer during a couple day stop in Post Falls. Then I will be back on the road. I wanted to take the time to get caught up on this thread.

That battery should work fine. That setup will allow you to use your 15w light for a couple of hours at a time but will still require 3:1 of off vs on time. For every hour of night riding, you will have to do 3 hours of day riding to keep the battery charged.

 

[Scotchmo]

If it ain't one thing its another. Referring to post #19, I attached the striped end of the recitier diode (276-1141) to the white wire. Then when I grounded the other end to the motor the motor died. So I then did it vica versa. I attached the non-striped end to the white wire and when I touched the other end to the motor the motor again died. That ain't right is it? Whats up?

Either your diode has an internal short or you have an unusual ignition system.

 

[Scotchmo]

Ok. To review, in my last post I did the test in post #19. I tried the rectifier diode in both directions and my motor died. That is not whats supposed to happen I don't think.

Next, I assembled the circuit without attaching it to the bike (1st photo).
After a few minutes the resister started getting very warm. Woops! I then removed the fuse so that my mockup would not burn up.

Now, if you look at the 2nd photo you will see a closeup of the busebar.
I experimented with the battery positive and my multimeter and found that voltage does go through the rectifier diode (from right to left) in the orientation that it is in but if I turn it around it would not. Therefore white wire will be able to supply voltage.

I have not tried turning the zener diode around because I have not been told if I can do that without ruining it. I can only assume that it is the reason why voltage is flowing to the resistor.

By the way, right now my battery is reading 6.36 volts on its own. When connected to circuit as in 1st photo it is reading 5.88 volts.

In both of my diodes (rectifier and zener) the stripe is on the left.
Should I turn my zener around.

Sorry for the long line of questions.

EDIT::
I did some reading and it seems that I need to turn my zener around. The voltage must travel from cathode to anode. But I need some verification from you. Please?

Your zener diode is backwards in the photo that you posted.

 

[Scotchmo]

IF you reverse the diode (changing from a positive to negative ground,) you also need to reverse the zener diode (and the battery.) (else, the zener acts pretty much as a short to ground, and does no regulation at all - all the voltage is dropped across the resistor.)

Now. Regarding the resistor. I've seen reports of unloaded voltages in the 20+ volt range when the motor is revving. This means that with the zener dropping apx. 7 volts, the resistor has 13 volts (or more) across it. P=e*e/r, so the power dissipation of the resistor could be 17 watts, or more... (assuming the polarities are OK.) Which explains why the 10W resistor is getting hot.

The most I've seen on a negative ground half wave is 8v or 9v peak. And you will never see 17 watts since you will be lucky to get 5 watts max out of the white wire. The 10w resistor should never get hot unless something is hooked up wrong or you have a blown fuse.