My converter power distribution panel has two fuses located off to themself labeled REVERSE POLARITY. These two large value ATC fuses are suppose to blow when connected in REVERSE POLARITY to protect things... If you are smoking battery cables then you have bypassed all of this added protection... Sparking battery terminals should have been your first clue something was wrong...
Two RED ATC 40A fuses shown here
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I have had excellent smart mode charging modes using my Progressive Dynamics PD9260C Smart Mode Converter/Charger unit. IOTA also is good multi-stage type converter/charger unit. Check with Randy at BESTCONVERTERS... Using any single mode type converter/charger unit will require you to keep a close eye on your batteries to check for boiling out battery fluids from being over charged using the single 13.6VDC DC output at high amps capacity... When the batteries boil out their fluids and go un-noticed it is usually GAME OVER for the batteries... Would be Lots of $$$ down the drain for me...
Roy Ken