Limit Voltage to Load
Use a voltage regulator between the charger/battery and the load. You say the load can tolerate a maximum of 14.5 volts so, if it nominally requires 12 volts, use a standard 12 volt regulator.

If you need to be able to produce 12 volts when battery and charger are only delivering (say) 13 volts, then use a low drop-out voltage regulator. 

If the current/amperage requirements for the load are above 1 amp then consider using a buck switching regulator with capability to work down to 13 volts.

If the current/amperage requirements for the load are above 1 amp and the charger/battery may drop below 12 volts, use a buck-boost switching regulator.