The first time the circuit breaker popped, it was because of some
electrical fault.
As others have described, the faults could have been battery, circuit breaker,
voltage regulator, ground wire, etc...

The second, third, and fourth times the circuit breaker popped, it was
because it had been reset by the pilot. The circuit breaker is installed
instead of a switch so that excess currents don't overheat the wiring.

Consider the possibility that the circuit breaker was good, and there
was a short
to ground on the field wire. Further suppose that the short was
heating enough to catch
the oily wire on fire right next to the other oily wires... or a fuel line.

In a 45 minute flight, a healthy battery should see you safely to the
completion
of the flight. Especially if you shed any unnecessary loads. If the
battery itself
is the problem, the handheld radio should get you back to a (VFR) airport.

-bob