HT 6v Charging System w/- ground

Scotchmo · Aug 11, 2009

loquin said:
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)

If you put a resistor in series with the charge current as you have done, you reduce the available charge current all the time. That circuit might be correct if your are building a general purpose 7.2v power supply with an ample input source (such as an AC supplied transformer). When powered by the white wire, your circuit will charge the battery some, but I guarantee that the circuit posted in the first post of this thread will charge much faster. Using a 7.2v zener is OK. Anything between 6.8v and 7.2v will work well enough. If you use a 5w 7.2v zener, you could probably eliminate the resistor altogether. If you use the 6.8v zener, put the resistor in the circuit, but in series with the zener regulator, not the charge current. In either case, the resistor will prevent overheating of the zener if you blow your fuse.

Scotchmo · Aug 11, 2009

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

As long as you have a battery in the circuit, the zener will be fine. If your fuse blows, the resistor will adequately protect a 5w zener.

Scotchmo · Aug 11, 2009

loquin said:
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.

The zener circuit (non-transistor) should not have a resistor placed in series with the charge current. The coil itself has plenty of resistance. Adding another resistor will weaken the charge even more.

Scotchmo · Aug 11, 2009

loquin said:
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.

A 5w or 10w, 10 ohm power resistor will not be fried by the white wire. It can handle a direct short indefinitely. The output of the HT white wire, negative ground system is fairly weak. Even without the zener regulator, I doubt that it would cook a typical 6v motorcycle battery. The battery could easily out last the motor. Some of the small 1960’s Honda motorcycles used no regulators, had higher output systems, and the batteries lasted long enough.

Scotchmo · Aug 11, 2009

Tinker1980 said:
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

The resistor should not be getting hot unless something is hooked up wrong or you have incorrect components. Earlier you said that you were using a 6v battery so that is good, but I should warn others not to use a 12v battery with this system. The resistor will get hot and the battery will get drained.

The 35w light should last about 20 minutes with the 2.5ah 6v battery. And then you will have to ride for 5 or 6 hours without running the light in order to get the battery fully charged. Since the white wire can only put out about 5w of usable power to charge, you have to know the limitations of the system to make use of it. I'm still looking to get a more efficient LED headlight so I can have a higher ratio of night time to daytime driving. You are not running the 35w light through a 10w resistor. The power flows from the battery directly to the light. Again, check your system. That resistor should never get warm when the headlight is on.

Scotchmo · Aug 11, 2009

Since there seems to be some confusion about the regulator circuit, I suggest running the simplified version with just the rectifier diode. It should work fine even without the zener and resistor. White wire to diode, diode stripe to 6v+ battery. Once you get this working right, you can add the regulator if needed, but you probably won't need it.

Tinker1980 · Aug 12, 2009

Scotchmo said:
The resistor should not be getting hot unless something is hooked up wrong or you have incorrect components. Earlier you said that you were using a 6v battery so that is good, but I should warn others not to use a 12v battery with this system. The resistor will get hot and the battery will get drained.

The 35w light should last about 20 minutes with the 2.5ah 6v battery. And then you will have to ride for 5 or 6 hours without running the light in order to get the battery fully charged. Since the white wire can only put out about 5w of usable power to charge, you have to know the limitations of the system to make use of it. I'm still looking to get a more efficient LED headlight so I can have a higher ratio of night time to daytime driving. You are not running the 35w light through a 10w resistor. The power flows from the battery directly to the light. Again, check your system. That resistor should never get warm when the headlight is on.

I don't use the 12v battery with the charging system. I've removed it, and may use it on another build once I can find a LED that lights up more than 5 ft of the road. The 12v battery is just wired through a switch, fuse, and a 55w headlight.

etacovda · Sep 14, 2009

tinker - i use these lights

http://www.dealextreme.com/details.dx/sku.11836

they're absolutely fantastic- theres several models of different ones on the site. the 5 led one would be fairly brutal, i would imagine - and probably around 15w max, given that that most of the singles are 3w.

michelevit · Oct 6, 2009

using capacitor instead of battery?

I live in the bay area, ca and there are many pc surplus stores.
Is it possible to use a capacitor instead of a battery? seems like
it would be smaller, lighter and quicker to charge.

any advice would be greatly appreciated.

white wire -> diode -> capacitor -> switch -> LED CREE Headlight

With winter quickly approaching I'd like to upgrade to a better lighting.

Scotchmo · Oct 7, 2009

michelevit said:
I live in the bay area, ca and there are many pc surplus stores.
Is it possible to use a capacitor instead of a battery? seems like
it would be smaller, lighter and quicker to charge.

any advice would be greatly appreciated.

white wire -> diode -> capacitor -> switch -> LED CREE Headlight

With winter quickly approaching I'd like to upgrade to a better lighting.

You could use a capacitor in place of the battery but it will not work as well. A battery stores a lot more than a capacitor. A battery likes to stay within a very limited voltage range so it acts as a voltage regulator. The capacitor will smooth out the voltage some. The lights will still go dim at idle and brighter at high rpm. You would have to limit the size of the lights since the capacitor will not have the reserve to run a high output light for any length of time. You would have to include the zener regulator if you are using voltage sensitive LEDs. Use of a battery solves these problems.

HT 6v Charging System w/- ground

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