My new Zamp 160 portable arrived yesterday and just some initial comments.
First, I wanted to see if I could just remove the battery clamps and use the SAE connector with the existing batteryminder eyelets that I have connected to the batteries. The SAE standard is for the bare part of the connector on the battery side to be the negative terminal. I batteryminder is set up that way as I understand the Renogy solar is as well. The Zamp connector is wired opposite to that, with the bare battery side of the connector connected to the positive side. Not sure why they don't conform to the SAE standard.
I set up the charger and connected using the battery clips to two group 24 batteries in parallel that had been on maintenance charge with the low amp batteryminder. The Zamp activated and briefly went into a charge mode but quickly went into float mode, suggesting the batteryminder was in fact keep the batteries fully charged. I did notice when in float mode, the Zamp charger showed 0.00 when I clicked over to the charged capacity (amp-hour) setting. I wonder if this only shows a value while bulk charging. I am reluctant to discharge the batteries while the unit is just sitting in my driveway to test this. I guess I'll find out when we go the Shenandoah Big Meadows in August without hookups.
So for now my plan is to try to keep the batteries charged off grid with the Zamp, use my Honda eu2000's on cloudy days, and bulk charge at home with the stock Parallax monitoring the current with my clamp on ammeter. When the charging current goes to a few hundred milliamps, I'll switch over to the batteryminder which seems to be doing a good job topping off the batteries and keeping them charged in maintenance mode.
I suppose one of these days I may bite the bullet and change out the Parallax for a 3 stage converter, but maybe my plan will work. We'll see.