It is not possible to answer this question without you telling us the current draw of each charger. We need voltage and wattage, or just the amperage of each charger.
Change the breaker to 50 amp, problem likely solved.
If it does trip that, you have too many.
Seriously depending on conditions and how the charger operates, you likely will hold more of them if they only need to "top off" the battery vs. if they are fully discharged.