Ammeter, volt meter, and stop watch get along nice. Again my point of view is generator run time. Without the benefit of solar panels. The ferro-resonant charger and Lombardidi and Trace does the 2-volt cells but the Lifelines are for my own use and are charged simultaneously when the 2-volters charge enough to back the generator down from 90% loaded. But that's why I have the BORG and the Frightening Harbor 700 watt. Which can only deliver around 500 watts of charging power with the yucky green 2-stroke. When the Kubota and 2-volt cells agree to a cease fire, the 2-stroke comes to life with the Borg set at 14.4 volts. One Megawatt active the 2nd dormant.
Full rave charging of both Lifelines is impossible using the setup I now have. And regulator substitution on the Lombardini is too much work. The one time I did it both Lifelines ganged were taking 223 amperes. Remember, one of the 2 group 31's is a 2-story model.