Some people like voltmeters over ammeter because they don't like that big wire coming and going in the passenger compartment. I think you need to look at the size of the wire going to the ammeter Is it big enough to handle the current. I believe most aftermarket wiring harnesse makers ASSUME you are using a voltmeter.
Jerry, an onboard hydrometer? I don't think I've every seen an onboard one. I have used the glass cylinder type many times. I would think you would have to have multiple sensors (one for each cell). Then rather that getting a value of specific gravity from each cell, have a warning pop up on the dash unit when the specific gravity falls below a set point and indicating which cell is failing. I know there have been DNF's in NASCAR due to battery failure plus the fact that the batteries (2) sit inside the passenger compartment. I had a battery explode on me years ago in a UH-1 Huey. It was not pretty. Got my [censored] chewed out for using one of those big fire bottles on wheels they park on the 'hard stand' instead of that baby one beside the pilot's feet. You may be on to something.
