I talked to the Next Gen about this.
What they said was that even with the same model generator, some battery chargers of the same make and model work and some don't. There was no apparent pattern.
What they suggested to do was to run a resistive load, like the water heater
coil, prior to turning on the battery charger. This was not effective.
So far I have had two ProMariner ProNautics fail. The third unit is on its way out.
Some manufacturers such as Xantrex and Master Volt "claim" that their chargers work with less than perfect AC generator output.
What I am looking for is anyone with actual experience with these or any other chargers. It seems like a lot of people on the board like IOTA
chargers, but there haven't been any responses here.