6 Volt Battery charger

I think it was Scotchmo who posted a simple charging circuit that runs off the white wire. It uses <$1 in parts and looks like it would work well.

just need to buy a bridge rectifier at radio shack about 2.99 if I remember right. Do a forum search and the wiring schematic should come right up.

ailgup said:

found his after reading more i think i will go with the 1/2 wave rectifier and some settup simmilar to this one http://motorbicycling.com/f4/6-volt-led-headlamp-w-small-3871-3.html#post92869

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My early system used a zener regulator. I have since discovered that you do not need it with the white wire ½ wave charger. All you need is the diode. Besides lead acid, it works well with a 6v lithium battery composed of 2 Lifepo4 cells.

ailgup said:

ya scotchmo i read that entire thread (13 pages of it) and derived that from it use the 1/2 wave with the diode, i think i will get a 6volt sealed bulb, i like that look, and then attach that to a 6c sla, i was wondering what the amp hour value you would recommend for that type of light?

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The size of the battery depends on the wattage of the headlight and how often/long you use it. If your headlight is <3 watts, even a tiny battery will do since the ½ wave charger can almost keep up with that load. If you use a high wattage headlight, the battery will only run it for a set period of time before you need to run with the headlight off in order to allow the battery to recharge. The brake light, horn and turn signals are intermittent and the charger has no problem keeping up with that load. I rarely run my headlight. I use to use a 6v 1.3ah SLA but now use 2x AA Lithium Lifepo4 batteries. I tend to use the lowest wattage components I can find and the smallest battery.

A standard 6v sealed beam is about 35 watts. Is that what you are proposing? That might be overkill for a 30 mph moped. You would then want a good size battery. If you intend to use it for ½ to 1 hour at a time, you will need at least a 6ah battery. And you will have to do 90% of your driving during the day in order to allow the battery to recharge.

Example:

If headlight wattage = 35w
and run time = 1 hour
then battery size = 35whr/6v = 5.83ah minimum
Recharge time (daylight use) 35whr/3 watts = 11.7 hours (and that is optimistic)

Things look a lot better when you use a small wattage headlight. The white wire charging system is suited to an intermittent low wattage electrical system. If you really need to use a large headlight for a good percentage of night time riding, then you will need to make other charging arrangements. An offboard charger can be used on it’s own or to supplement the ½ wave charger.