I used a Samlex America model SEC 1223. 13.8 volt, 23A (not 4O amp) unit.
I connect mine right to the leads-alligator clips-taken off the battery. This allows me to turn off power with master switch at panel, if necessary.
Moved to Murphy, NC
repeat offending-8A N116TP-Now Flying
based in Copperhill, TN 1A3