I've got a 1966 Atlas that was fitted with Boyer electronic ignition when I bought it, but it went wrong, so I refitted the magneto. This is fine, but the charging circuit now puts out a steady 6-8 Amps all the time, which isn't being used, so I'm blowing bulbs all the time if I put the lights on. Even with all the lights on, the charging circuit still shows a positive charge of about 4 Amps & if I go over about 60mph/3500rpm the headlight bulb blows immediately. I've tried heavy duty bulbs in case it is vibration, but this has no effect. Also with only a 9AH battery fitted (this is all the battery box will take) the battery has boiled dry and died. When the battery died, the charging system stopped working until a replacement was fitted. A friend has suggested that I need to fit a "dropper", but when I Google these, they seem to lower the voltage rather than the current which is not really what is required? They also get hot apparently and need a heat sink? The Zener & rectifier appear to be OK (have been replaced anyway). It would seem that I need something that provides some sort of resistance to supplement the Zener, but being an electronic duffer I don't know how I'd wire it in. Has anyone any suggestions please? Or have I got a more serious electrical fault somewhere?
I have a 62 Atlas with 12…
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Hi The symptoms point towa…
Hi
The symptoms point toward the zener diode not limiting the voltage in the system, as this is a new component perhaps the wiring is faulty, Check there is a good connection between the body of the diode and the frame of the bike.
Briefly :- The alternator produces an AC, the rectifier converts this to DC. As the speed increases so does the output of the alternator. A 12volt Lead Acid battery requires about 13.8volts to keep it fully charged, the system output is therefore limited to around this voltage. Itâs the job of the zener diode to do this by acting as a bypass of any excess voltage.
The voltage of lead acid battery will under normal charging condition will FLOAT upto the charging voltage 13.4 â 13.8 but will NOT be passing any significant current, 1 amp Max
Ron C.
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Previously wrote: Hi The s…
Previously wrote:
Hi
The symptoms point toward the zener diode not limiting the voltage in the system, as this is a new component perhaps the wiring is faulty, Check there is a good connection between the body of the diode and the frame of the bike.
Briefly :- The alternator produces an AC, the rectifier converts this to DC. As the speed increases so does the output of the alternator. A 12volt Lead Acid battery requires about 13.8volts to keep it fully charged, the system output is therefore limited to around this voltage. Itâs the job of the zener diode to do this by acting as a bypass of any excess voltage.
The voltage of lead acid battery will under normal charging condition will FLOAT upto the charging voltage 13.4 â 13.8 but will NOT be passing any significant current, 1 amp Max
Ron C.
Hi All
There is some half truths here. You should NOT be over charging IF the Zener is properly connected and it is in good order. BUT a suspect rectifier won't help either. NOW take note-if you try using a Zener as a regulator with a magneto and by chance you have a decent alternator you will still be in trouble as the lack of coil current will allow the Zener to be over loaded and blows, back to square one. You can get round this by retaining the original 6V alternator wiring/switch business, or you could fit a modern regulator/rectifier (Or refit coil/electronic ignition).
Charge voltage-at 13.8 this is only adequate. You need 14.4 ish. Not above 15V and anything below 13.5 is inadequate. By the way although the Zener has been with us for many years and a good one used safely (NOT with magneto)can give you good battery charging but they can be very variable. By the way I can test them. The modern regulator rectifiers-Boyer Power Boxes etc can also be variable, although some new ones (from China) seem to be doing the 'business'
Al Osborn Electrical person for NOC.
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I have a 62 Atlas with 12 volt alternator and magneto system. The Zenior diode needs to be mounted tight to the heat sink with good electrical connection at ground. the Atlas had the "flying saucer type , I made mine from 1/8th" aluminum sheets cut round with hole saw and hanging from a mountfittedto the gas tank to frame bolt .you can probably still buy them.I have had no problems with headlite or battery. The Zenior controls the charge so I would look there first. Some may know whybut I think that if the battery has a dead cell it can confuse the charging system and cause overcharging as well? i have ridden several hundred miles trips with this set up.