Choosing the Right Marine Battery

Flooded Batteries

Also referred to as “wet cell”, flooded batteries use a reservoir of liquid sulfuric acid between their lead plates that produces hydrogen and oxygen when the battery is being charged. Because of the hydrogen, the batteries must be vented to allow the gas to escape safely. Without this, they would overheat and boil over – so you must ensure these batteries have adequate space for ventilation. Flooded batteries also need distilled water added regularly – so make sure you have a way to access them easily.

AGM

Absorbent Glass Mat (AGM) batteries are sealed, so they don't have the same ventilation requirements as flooded batteries. While technically a type of wet cell, in absorbed glass mat batteries, the positive and negative plates are separated by an absorbent fiberglass mat that holds the acid electrolyte like a sponge. This minimizes the potential for electrolyte spillage. During the charging process, these batteries have pressure valves that allow the oxygen from the positive plates to move to the negative plate, where they recombine with hydrogen, producing the water that the battery needs – so there is no need to top up! While these are a sealed battery, they do have a pressure relief valve that can release excess pressure if needed – and so require adequate ventilation. AGM batteries are deep-cycle batteries. Deep-cycle batteries, like the Optima Blue, are batteries that can be discharged and recharged repeatedly without losing their capacity or performance. AGM marine battery technology is improving, so it pays to do some research to make sure you are getting the best bang for your buck!

Gel Batteries

Gel batteries are popular in marine applications due to their unique properties. Unlike traditional lead-acid batteries, they utilize a thickening agent to create a gel-like substance, offering significant advantages for marine use. One key benefit is their exceptional cycle life, providing up to three to four times the lifespan of standard AGM or flooded batteries, making them a cost-effective choice. Additionally, gel batteries boast a higher depth of discharge, allowing you to utilize up to 100% of their capacity without damage, ensuring extended usage without worrying about power depletion.

Their resistance to vibration and shock makes them ideal for marine environments with constant movement, ensuring durability even in rough waters. Gel batteries also function well in a wide range of temperatures, from hot tropical climates to freezing regions, maintaining consistent performance. Moreover, they recharge faster than AGM and flooded batteries, offering quick turnaround times for marine enthusiasts needing rapid power replenishment between adventures. These features collectively make gel batteries a reliable and efficient choice for marine enthusiasts seeking high-performance power solutions.

LiFePO4 (Lithium Iron Phosphate)

LiFePO4 batteries are making big inroads into the marine market and, while expensive, have quite a few benefits over standard battery types such as flooded and AGM. Not to be confused with Lithium Ion, LiFePO4 batteries use different materials and are far more stable (i.e., safe) – making them highly suited to boating applications. LiFePO4 batteries are sealed and can withstand a much higher temperature range without any performance loss. They have the advantage of less weight, offering 3 times the life cycles, and can take a far lower depth of discharge (up to 100% vs. 50%). Additionally, they can accept much higher charging amperage than traditional AGM or flooded batteries – which means they charge in a fraction of the time to get back to 100%. Despite the higher price, many consider these LiFePO4 batteries to be the best marine batteries.

So what's the downside? These batteries are more expensive (but when you compare pricing, remember that you can use 100% of the stated Ah capacity of a LiFePO4 battery vs. only 50% of a lead or traditional AGM) and are particularly sensitive to charge requirements

A Few More Important Things to Remember…

When buying a new set of batteries, it's imperative that you not only purchase the same type of batteries (Flooded, Gel, AGM, or LiFePO4), but that they are made by the same company and manufactured around the same date. It's never a good idea to combine batteries that have different “birthdays”. If you do – the older battery will often negatively affect the performance of the newer batteries.

Having the same type/manufacturer of batteries is also critical, as all batteries use different charge profiles (determined by their manufacturer) – so they cannot be connected to other types/manufacturers of batteries and still be charged correctly. It's important to consider all of your needs onboard before making your choice.

One more important thing to remember – when choosing the best battery for your boat, you must make sure that your charger is set up with the correct charge profile for the battery type you have selected – or you may be buying new batteries a lot sooner than you expected! Today's “smart” battery chargers can usually handle any type of battery if you choose the correct settings. In addition, newer chargers monitor battery charge state to provide the optimum charge process – providing for the fastest recovery and ideal conditioning – which can lead to a longer life span for your batteries. If you haven't bought a new charger in a while and you are planning to invest in new batteries – now is the time to upgrade! Fisheries Supply carries a multitude of batteries and accessories.

What features should you look for when choosing the best marine battery?

When choosing the best marine battery, look for features such as deep cycle capabilities, high reserve capacity, maintenance-free design, and durability. Additionally, consider the battery's size and weight to ensure it fits your boat's specifications and is easy to handle.

What is the best amp hour for a marine battery?

In order to start the engine, a starter battery should be able to deliver 75 to 400 amp for a short period, between 5 and 15 seconds, but it does not need to have a high storage capacity. On the other hand, a marine "house" battery only requires approximately 80 amps but should have the ability to run for extended periods of time.

Finally, if you aren't 100% sure about how to set up your electrical system, we highly recommend that you hire an experienced installer.

We hope this Navigator has been helpful. If you have any additional questions about batteries for boats, best marine cranking battery or need clarification, check out the other battery topic links below, or feel free to contact our battery experts at (800) 426-6930.

Marine Battery Basics

How to Size a Marine Battery Bank

Charging a Marine Battery

Marine Inverter Basics