Great thread! Thank you.
I went with the Graywacke slave setup.
I use the 24Volt Pulsetech unit.
However I am having trouble getting the unit to work past the "no battery connection" warning.
I run a keyed battery cutoff switch at the battery cover. It does not charge whether switch is in on/off position.
I would suggest that if your batteries really die, that they be charged 12v individually. The slave port works good for charging and trickle charging. Every now and then I take off the slave port connector and put the clamps on, and give the batteries a individual charge check-up.
Double check your wiring in the graywacke connector. - and + setups.
Double check that the slave port itself is connected and working too.