Chris,

On our SM, the main circuit breaker is also a GFCI.  On mine, this is indicated by a label reading "I∆n = 0.03A" on the circuit breaker, which means it has a 30mA ground fault limit.  Given that your breaker is tripping instantly and there is no sign of overcurrent (presumably the branch breaker for the charger is of a lower rating than the main one, so it should trip first), I bet you're seeing a ground fault.  This could be due to a failure inside the charger or something entirely unrelated.  Is the charger specified to accept both 50Hz and 60Hz AC?

Ryan and Kelly

SM 233 Iteration

Boston, MA, USA

On Wed, Jul 22, 2020 at 1:49 PM Craig & Katherine Briggs SN 68 Sangaris Tropic Isle Harbor, FL via groups.io <sangaris=aol.com@groups.io> wrote:

Chris,
I agree with Bill, although I would note the Victron is the large 100amp charger and the Chargemaster is the small 40amp one - you may have reversed that in your post. A starting point may be to check the connections at the circuit breaker of whichever unit it is that's tripping the mains and at the unit itself. 
Both units are 3 stage chargers and the step down points are controlled by the battery voltage, not by the % charge, so, no, you can't adjust for that. There are some adjustments you can make that are covered in your instruction manuals, but it's unlikely any are needed.
Sorry, but can't help with where your inverter is.
Assume you're in the US with 60Hz - where?
Craig