Adding a second battery is not a bad idea, but it all really depends on how big your electrical load is. You are probably running basic electronics, a FF, gps and vhf. The engine alternator can handle all of this. Your biggest issue is having a good quality battery that has the power to handle what your trying to power. As batteries get older they do not hold a charge as well and take longer to charge, making your alternator work harder. My recommendation, whenever you buy a boat, replace the batteries so you know they are new and will not give you issues. A second battery is not a bad idea since you are running your electronics and starting your batteries off the same battery/batteries, this gives you added safety incase you do have a load draining your batteries. Always buy identical batteries and replace them at the same time, do not mix and match, they will charge at a different rate if they are a different age or type/size and one battery will be over worked and the other will have little benefit. If you do not come down for a week or 2 at a time, a battery charger is not a bad addition. The charger is not expensive, the promariner is a good unit for your size boat and is under $200. You will also need a shore power chord, another $100+ depending on length you need, and the adapter as well so it can add up, but it gives you peace of mind that when you get down to use the boat your engines will start and your batteries will be topped off and you will not have surprise dead batteries when you bring guests or the family. If you plan to keep the boat, a charger would be a wise investment, it is not an absolute neccesity, but it will keep the batteries topped off and keep you on the water which is well worth it. If you do not use the boat frequently, more reason to have one.
Enjoy the new boat and welcome to the forum!!
