HT 6v Charging System w/- ground

Discussion in 'Electrical' started by Scotchmo, Jul 23, 2009.

  1. Scotchmo

    Scotchmo Member

    People have implemented numerous different configurations of charging systems using the white wire on an HT engine. This thread will be devoted to one particular version; a 6v, negative ground, lead acid system. A few people, including myself have had success with different versions of it. It can keep a 6v lead acid battery charged during regular intermittent usage or occasional heavy usage. The main limitation is the minimal charge current so it is not suitable if you do all your driving at night. With the proper battery, it can handle occasional night driving even with a high output headlight.

    We can start with the simplest system that requires only a diode, battery, and fuse. The battery acts as a voltage regulator and keeps voltage within a narrow range so that you do not burn out sensitive components, or suffer from dim lights at low speeds. The fuse protects your wiring and the diode rectifies the current in order to charge the battery.

    A small 6v motorcycle battery is a good choice to use in the simplified system. These are typically wet cell batteries in the 2ah to 8ah range. They are somewhat tolerant of overcharging so should do the job even without a charge regulator. Later, you can add two more components to implement a zener diode charge regulator. That will prevent even smaller, sealed lead acid batteries from overcharging which could happen if you drive often but never use your lights.

    Except for the optional zener diode, all of the components are available at Radio Shack. The ratings for the components are in the ballpark but we may be able to use even lower wattage items. The use of a terminal strip means that you do not even have to solder any components. I would like to see some people implement the simple system and report back on the results. We can then discuss limitations and possible improvements, as well as coming up with optimal components. Suggestions for suitable 6v lights, horns, bulbs, LEDs, etc. are also welcome in this thread.

    The first image shows a mock up of the simplified system.

    The second image shows a mockup of the zener diode system.

    The third image shows a diagram of the zener diode system.

    The forth image shows the battery box that I used on my system.

    The bill of materials below is for the zener system that I am currently using. For the simplified system, you only need the rectifier diode, fuse, and any 6v lead acid battery.

    Terminal strip - Radio Shack 274-679
    WHITE 18g wire - to motor
    RED 16g wire - to light, horn, switches, etc.
    BLACK 16g wire - to motor or to ground
    D1 - rectifier diode, I used Radio Shack 276-1141
    Z1 - zener diode, 6.8v, 5w - 1N5342B
    R1 - power resistor, 10ohm, 5watt, I used Radio Shack 271-132
    F1 - fuse, I used a 5 amp fuse
    B1 - 6v lead acid battery, I used a 1.3ah SLA
    Battery box - 2.0x2.5x5.0 plastic Radio Shack project box
    Mounting brackets - plastic conduit clamps from Home Depot

    Attached Files:

    Last edited by a moderator: Dec 15, 2015

  2. sofasurfer

    sofasurfer Member

    A slight un-understanding on my part... Am I correct that in the 1st attachment (mockup-simple) the battery is grounded to chasis and in the 2nd attachment (mockup-zener) the battery and terminal strip are both grounded to chasis?
  3. Scotchmo

    Scotchmo Member

    You are correct.
  4. Tinker1980

    Tinker1980 Guest

    The parts aren't available at my local Radio Shack... I asked for a few of these, even had the Radio Shack part numbers... problem seemed to be, I wasn't buying a cellular phone or flat TV so they weren't prepared for me. The poor young woman at the store, attractive as she may have been didn't know what a zener diode was. They did have some PC boards though. Kinda sad what they've become lately.

    I did manage to get the parts (from another place in Tulsa) and with my lovely wife wondering what I was doing, I put the circuit together. It's the first component-level soldering I've ever done! And it works great. Only difference in my setup is the battery, and the power resistor. I accidentally got a 10 watt instead of a 5 watt, and my battery is a 2.5 ah instead of a 1.3. I had an old spotlight with a 2.5 ah 6v SLA battery and used it.

  5. Scotchmo

    Scotchmo Member

    It is great to hear that you got a working system put together. The 10w resistor is fine, just a little bulkier than needed. That is what I used since that is all they had. I almost picked out that same battery but decided on a lower capacity one in order to save on weight and size. The 2.5ah spotlight battery will allow you to use your headlight for longer continuous periods of time. Are you using the spotlight as your headlight? That might be a good idea. It could be your headlight and hold the battery. You just need a good way to mount it. The selection of electronic components at Radio Shack is pretty slim these days. You won't find a suitable zener diode there. Did you find a 6.8v, 5w zener diode at the other store? Or something close? Since our town's last real electronics store closed a couple of years ago, I've had to order many of the parts that I need. I too soldered my final system before installing, but the terminal strip is nice for testing and actually works well. It makes it easy to swap components. Keep me posted on the longer term results.
    Last edited by a moderator: Dec 15, 2015
  6. sofasurfer

    sofasurfer Member

    In attachment "mockup-simple", I see that the battery is supplying the lights. And you state that "the diode rectifies the current in order to charge the battery". But it looks to me like the white wire feed is flowing back through the current going from battery to lights. Is this correct/possible? Or am I misunderstanding.
    Forgive my basic ignorance of electrical circuits.
  7. Scotchmo

    Scotchmo Member

    I don't fully understand your question, but I'll do the best I can. The white wire "feed" goes through the diode and then into the electrical system positive pole. The diode acts like a one way valve. Current cannot flow back through the diode so the only two possible places for the white wire current to flow is either into the battery or into the lights.

    In the simple system, any excess current is burned up in the battery. In the zener system there is a third possible destination for white wire current. Any excess white wire current is burned off in the power resistor. Here is an explanation of current flow in the zener system.

    motor off, lights off - No current flows.

    motor off, lights on - Current flows from the battery to the lights.

    motor running, lights off, battery fully charged - When white wire voltage is below the battery voltage, no current flows. When the white wire voltage rises above 6.8v, current is shunted through the power resistor.

    motor running, lights off, battery below full - When the white wire voltage rises above the battery voltage, current flows into the battery to charge it.

    motor running, lights on - Current flows from the battery to the lights. All white wire current flows to the lights. The white wire only flows current when it produces a voltage that is higher than the battery voltage.
    Last edited by a moderator: Dec 15, 2015
  8. sofasurfer

    sofasurfer Member

    You did a perfectly great job of answering my question.
    I just realized that this system works similar to when you have an electrical generator (such as wind turbine) powering you're house and if you get excessive voltage it feeds back into the public power grid and is used up in a differant place.
  9. sofasurfer

    sofasurfer Member

    I understood perfectly, but when you stated "In the simple system, any excess current is burned up in the battery" you caused another question :) I have never heard that current is "burned up" in a battery. A battery charger shuts off when a battery is fully charged. But it never occurred to me what would happen if the charger was defective, for example, and did not shut off when the battery is fully charged. How does a battery "burn up" excess current?
    Last edited: Jul 25, 2009
  10. Scotchmo

    Scotchmo Member

    Once the battery reaches 100% charge, additional current will cause gassing or electrolysis. This releases heat and can cause loss of electrolyte. On a standard lead acid battery, you can replenish the lost water. On a sealed lead acid battery, a small amount of overcharge can be tolerated as the gases will recombine. Too much overcharging of the sealed battery will cause it to lose capacity permanently.

    On the zener system. The zener diode "shuts off" the charging when the battery voltage reaches our zener voltage (6.8v). In the simple system, the charging only shuts off when the voltage of the white wire drops below about 6v. A lead acid battery can withstand some overcharging. And you can overcharge almost indefinitely as long as the charge current does not exceed 1% of the amp hour capacity of the battery. So battery life could suffer in the simple system, especially with small, sealed batteries. So a non-sealed motorcycle sized 6v battery may be the best choice if you go with the simple system. Until we get more user test data, we won't know how small of a battery we can use with the simple system and still get adequate life.
    Last edited by a moderator: Dec 15, 2015
  11. sofasurfer

    sofasurfer Member

    I'll be darned!
    You could pass for an electronics teacher.
    I now know more about electronics than I ever did before.
    Last edited: Jul 26, 2009
  12. Tinker1980

    Tinker1980 Guest

    I used to have the spotlight mounted to the handlebars on the bike, it had a LED and a halogen light, you could use one or the other. The LED was pitiful, could hardly see past the front tire, the halogen was really bright, but would only stay on for 15 minutes or so. I have considered using a 6v bicycle headlight or even a 6v flashlight with this setup, either would be bright enough for my needs. The spotlight bulb is 6v and 35 watts, so to run it longer I would just need a bigger battery. I don't know that a bigger battery would get a very good charge from the little magneto.

    I did find a 6.8v 5w zener diode at my new favorite electronics store. (Affiliated electronics) I'm now looking around the house to see if there is a small enclosure I can use to hold the battery and the charging circuit, I may end up using a small piece of PVC for it all.

    Last edited by a moderator: Dec 15, 2015
  13. Scotchmo

    Scotchmo Member

    That 35w bulb might be optimum for lighting up the road. But I too am going to look for a better compromise. My 6v generator headlight is just adequate so I still want to try an LED bulb of similar wattage. From reading other posts, the maximum wattage available from the white wire is about 5w. In my tests, I got considerably less. Even at the optimistic 5w maximum, the 35w light would require 7 hours of daylight driving for every hour of night driving. And you would need at least a 6ah battery to run the light for 1 hour continuously. The system could charge almost any size 6v lead acid battery but I think 6 to 8ah is about the practical limit.
  14. Tinker1980

    Tinker1980 Guest

    For my commute home after work (at 3 am) I need about 20-30 minutes of really bright light, the other 15 minutes or so are along well lit streets. Nice thing is, from what I've seen, a 6ah 6v battery is much cheaper than a 6ah 12v battery. And just to sweeten the pot, I come to find out that the 6v light bulb is exactly the same shape and size as the 12v light bulb I have in another light... I put the 6v bulb in the 12v light (it came from a forklift) and now it's even *brighter* than the spotlight since it's shining through the Fresnel lens that's part of the forklift headlight. And of course, the light already has a bracket for mounting, and will take far more punishment than a motorized bike on bad roads can deal out.

  15. Scotchmo

    Scotchmo Member

    The 6ah 6v battery should be cheaper and about half the weight. If you want to match the capacity of the 6ah 12v battery, you will need to get a 12ah 6v battery.

    volts x amp-hours=kwh/1000

    12v x 6ah = .072 kwh
    6v x 6ah = .036 kwh
    6v x 12ah = .072 kwh
  16. loquin

    loquin Active Member

    The pneumatic/hydraulic equivalent of a zener diode is a pressure relief valve. When pressure gets too high, the pressure relief valve opens, allowing the excess pressure to bleed off. A spring loaded valve will close when the pressure drops a bit.

    With the zener diode, when the voltage (pressure) gets too high, the zener diode (relief valve) resistance drops to a lower value, allowing the excess current to bypass through the resistor. The circuit isn't very efficient though, as all the excess is wasted as heat in the resistor. It's a simple, easy to build circuit, though.
    Last edited: Aug 2, 2009
  17. Scotchmo

    Scotchmo Member

    I like your pneumatic/hydraulic analogies as applied to electronic components. They are more intuitive than electron behavior.

    The zener regulator does indeed waste all excess charging energy but overall, it ends up being only a small amount. It is a small price to pay for having a fully charged battery ready to go. Even when the battery is full, no power is wasted until the white wire voltage rises above 6.8v. And even at that point the opposing emf of the battery allows only the peak of the wave that is over 6.8v to be wasted.

    These HT motors are all about simplicity. The excess charge is so small that many implementations may not even need the regulator. Some users may even find the rectifier diode/battery/fuse system is more complex than they want or need. They just run the white wire directly to a light. It has it’s drawbacks, but it works for them. The simplified battery system and zener regulated system described here are both compromises but still allow implementation of a full electrical system without being overly complex.

    The simplified system is similar to early 1960s Honda motorcycles. Silicone diodes of that time were either inadequate or unavailable so they used selenium rectifiers. The 1960's British motorcycles used a zener regulated system. And they were burning off relatively large amounts of power through the zener diodes. So I believe that we are using the appropriate solutions, with more modern components.
    Last edited: Jul 29, 2009
  18. sofasurfer

    sofasurfer Member

    Got all my parts today. Hope to get the battery this weekend.
  19. Scotchmo

    Scotchmo Member

    Before you assemble your charging system, try this test. At idle, hook one end of the rectifier diode up to the white wire and short the other end of the diode to the motor. If the motor dies, reverse the diode and try it again. The motor should continue to run even with the shorted diode. That is the correct polarity to use. If the diode stripe (cathode) is toward the white wire, then you will need to configure for a positive ground system, otherwise, use the negative ground system.

    I have heard that other HT motors are better suited to positive ground but I have yet to find one. This simple test will determine how to set yours up. Please report back with the results.
  20. Scotchmo

    Scotchmo Member

    I'm going to have only occasional internet access for the next 4 weeks. I'll be touring the northwest on my other bike (Goldwing). I'll check back in on this thread when I get back.
    Last edited by a moderator: Dec 15, 2015