When using multiple power sources to charge a battery, they can often compete with one another. For example, if your solar panel or wind generator is charging the battery at 14 volts and 10 amps, the regulator sees this as a full State of Charge (which it isn’t).

Under these circumstances, the alternator will only output a minimal current instead of doing its job effectively. In other words, the alternator won’t be working optimally and the solar panel’s input will be limited to just 10 amps – an inefficient situation that isn’t damaging but not ideal either.