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Sunlight is only available for a couple of hours each day for meaningful use with solar panels. You’ll need to store the excess energy for later use at night when there is no sunlight or pull constant power even in bad weather conditions. So you need a battery that will provide long periods of discharge and fully recharge in a few hours of sunlight . The battery you’ll need is a deep cycle battery.
While some marine batteries have been labeled as deep cycle batteries most of them are hybrids and fall between starter batteries and deep cycle batteries (more on this later). A deep cycle battery with a good cycle life will cost you a good amount of dollars and with bad handling they won’t last long. Getting a marine battery whether a true deep cycle or a hybrid will not only save you money but with good care can last as long an expensive one.
I would recommend getting the Renogy 200 Ah Battery. I use it to run a 130 W refrigerator for 24 hours. It works with 80% efficiency and can be discharged up to 50%. It can also power my tv and fan when I disconnect the fridge.
Also check on these two below:
VMaxTank Deep Cycle Batteries
Weize 12V 100AH Trolling Motor Battery
Types of Marine Batteries
Like stated before there are three types of Marine batteries you’ll find in the market: A deep cycle, starting and Dual purpose or hybrid.
A starting battery unlike the deep cycle battery is design supply an initial burst of power to get an engine running. The starting power of a Starting battery is measured by Cold Cranking Amps (CCA) which is the amps the battery can deliver in 30 seconds at 0°F.
A starting battery isn’t suitable to be used as for deep cycle charges like in solar system or on a trolling motor. It’s job is to only start the battery.
This type of battery is characterized by large number of thin plates which presents a maximum surface to the electrolyte therefore enabling it release a high current to start a boat’s engine.
Deep cycle battery
A deep cycle battery is designed to supply a constant and steady supply of power. This allows them to run for a long time until discharged (up to 80%) and then recharged.
So instead of providing a surge of power over a short period of time a deep cycle battery will provide a constant charge over a longer period of power. This allows them to sustain loads in 12v or 24v systems including solar systems.
The battery is characterized by thicker and fewer plates compared to the thin plates of the starter battery. There is less surface to react with the electrolyte so current release is slower therefore ideal for a steady draw.
A hybrid battery is also known as a dual-purpose battery. It acts as both as a Starting and Deep Cycle battery. The battery tries to deliver high discharge currents without excessive voltage sag up. They however cannot deliver a very high starting current as a starting battery and the cycle life is half of that of true deep cycle battery.
You can also a hybrid battery in a solar system but it won’t last as long as a true deep cycle battery.
Qualities of a Good Marine battery
While type is one of the differentiator of marine batteries there are other features that will vary from each brand giving you a difference experience.
So it is important to be able to pick out a good quality battery.
Maintenance and Design
Older types of lead acid batteries required constant attention in checking leakages and refilling with water. They also produced toxic gases and therefore needed good ventilation.
The new sealed batteries require zero maintenance and making them easier to own and use. AGM batteries used “Absorbed Glass Mats” between the plates. The electrolyte is contained in the glass mats. They therefore cannot spill even when broken. They are also safer to mount in positions that would otherwise damage conventional lead acid batteries.
A battery’s reserve capacity is the amount of time required for a fully charged battery to drop below 10.5 volts while discharging. The higher the battery’s reserve capacity the longer it’s capable of performing.
Date of Manufacture
Over time, batteries gradually begin to lose their effectiveness and stop being able to maintain a charge as effectively as they once could. Even if it’s completely new and unused, a battery that’s one year old won’t perform as well as one that was just delivered from the factory.
While marine batteries can be used in a solar system. It is recommended you go for a true deep cycle battery that will not only last long but reserve more power. The best batteries for solar are lithium batteries; They offer a deep discharge of up to 90% and are also very efficient. However they are quite expensive and you can opt the new AGM batteries that give you great performance as well.