never had a problem with the last3 trailers. add a marine shut off switch too. one that allows battery 1,2,both or off.
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It was a rainy few days at Algonquin Prov park...tarps kept us dry.
Wayne --Belle River (Windsor), Ontario
2013 Sunset Trail Reserve 25RB..(just sold it)
2015 White Chev Silverado 2500HD 4x4 (6.0 l gasser)
2003 Mountain Star 890SBRX Truck Camper
No issue adding a second battery. Wired in series if 6v, parallel if 12v.
It will take longer to fully charge more battery density but you'll also get longer results.