12V regulator to condition output from alternator

I have a Briggs and Stratton 24 hp 2 cylinder engine. It has its own battery for the electric start.
I also have some microprocessors mounted on the lawn tractor powered from a separate 12 battery.
I would like to the motors charging system to also charge the second battery so that I do not need to charge it every night. However I would need all current and voltage spikes to be regulated out of the charging process to the second battery so the electronics are not blown.
any ideas

Hi Max,

Thank you for contacting Digi-Key. Make sure the alternator is large enough to charge both batteries. If the alternator is not large enough to charge both batteries it may generate excess heat or destroy the alternator or alternator regulator.

Some alternators have regulators built in them (like modern vehicles), and some have the regulator external to them (older vehicles and some small engines) but as far as I know all alternators have a regulator, as these are required to prevent overcharging of the battery. An alternator system without a regulator would constantly destroy batteries from over-charging if they did not have a regulator. Assuming it would have a regulator, it should be outputting somewhat clean power as these are somewhat of a filter on their own. Depending on the exact set-up, there are sometimes further filtering. Selecting a component can vary on the exact voltage output across the battery while the tractor would be running. Do you know the voltage produced while the tractor is running?