When not running the battery in my 65 Atlas reads 12.9 volts and when it is running and reved up some it goes to 13.7 volts, is this charging?
The ammeter goes a little to the right but the headlight stays about the same brightness.
Thank you in advance
12.9 v is a healthy …
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Hello Jim and Robert, 13.7 V…
Hello Jim and Robert, 13.7 V could easily be the clipped voltage after the zenner diode has done its job. The battery should still charge happily with that sort of voltage applied across it. Remember to keep the zenner and its heat-sink in the airflow,Cheers, Howard
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If it is....
If it is a lowish Voltage (13.7 is lowish) then disconnect the Zener, then run the engine up, The battery voltage should rise to 15V or more. Perhaps with headlight on it will be a bit lower. This proves there is plenty from the alternator. And the Zener is on the low side. If the voltage does NOT rise above 14V then the alternator/stator is suspect.
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12.9 v is a healthy voltage for a battery that has been standing . A running voltage of 13.7 means the bike is charging and is probably good enough for the usage the bike is getting.. Better if it was somewhere over 14 v to ensure enough for winter or night riding in slow traffic , but do you do that??. Worth cleaning connections and trying another zener / control box as the cutoff voltage of these can vary. When we are forced to run with daytime lights many a classic could struggle , Those with the old mags will have the last laugh as they keep going.