Solar energy provides an easy solution to maintaining high battery voltage for deep cycle batteries used in boats and RVs. It is important to maintain a high voltage as low charge can reduce a batteries lifespan by 2-5%. It is recommended that a charge controller is used with the marine solar panels to ensure the uncertain voltage from a solar panel will safely charge a battery.

What is a charge controller?

A charge controller is a regulator that goes between the solar panels and batteries designed to keep the batteries at peak charge without overcharging.

What are the main types of batteries used with photovoltaic systems?

Almost all of the batteries typically used in PV systems are lead acid.These batteries are ideal for portable power systems due to their high power to weight ratio.

Deep cycle batteries are designed to deliver a consistent voltage while the battery is discharging. These batteries are ideal for the large power draws of electronic systems on boats and RVs.

Starter batteries are designed to deliver sporadic voltage spikes. These large surges can be used to start the motor of a car, van, motorcycle etc.

The main structural difference between these two types of batteries is in the composition of the lead plates. A deep cycle battery has solid plates while a starter battery has plates that are porous and sponge-like.

Most marine batteries are a hybrid of deep cycle and starter batteries. The plates are made of a lead sponge that is coarser and heavier than a typical starter battery plate.

How far can a battery safely be discharged?

Deep cycle batteries can be discharged down to 20% of their charge capacity.

Starter batteries should not be discharged below 80% of their charge capacity.

Hybrid batteries should not be discharged below 50% of their charge capacity.

Repeatedly discharging a battery below these recommended levels will shorten its lifespan.