HT 6v Charging System w/- ground

Scotchmo

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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
 

Attachments

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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?
 
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 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.

-Mark
 
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.

-Mark

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.
 
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Question.
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.
 
Question.
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.

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.
 
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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.
 
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?
 
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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?

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.
 
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