Speaking of 16 volts.....

[Rich Biebel]

Ed.....rectifiers in a battery charger are similar to what is in most old style welders with DC weld output. There are various designs but most often is a set of diodes mounted on a set of plates. A diode does one of two things......dead shorts or blows open. In a dead short the machine will often blow the AC line breaker feeding it when it is turned on. If the diode blows open.....no DC output....and seeing an AC output on the DC output side is not something I have ever seen.

One issue you could easily have is a generator that is running at too high a speed and this will cause it to put out too high an AC voltage. Their voltage regulators can only regulate properly if engine speed is close to what it should be......So if you are putting well above 120 volts into your battery charger your DC output will be higher......I have seen generators go to max voltage with failed regulators. Even at normal engine speed the AC output is up to 160 volts.

Had a buddy lend his cheap generator to a guy when we were racing one weekend this past summer......I thought his generator sounded like it was running fast but it was dark and we were busy......a few minutes later the battery charger the guy was using went up in a shower of sparks and smoke........Sad part is the generator was one he got from my place and he had lots of use on it.....somehow the throttle hung up and no one noticed until it was too late.......1 scrapped battery charger and we scrapped the generator.....it was not worth messing with.....he got his use out of it and it was as cheap as they come....Offshore built.....He bought a Honda to replace it.....2 of them...

[Ed Wright]

Rich, I have had leaking diodes in automotive alternators allow some AC voltage. The automotive ECUs hate it. I don't know if a battery charger can do that. Mine shows 40 volts AC plugged into the wall in my garage.