How to Choose A Boat Battery (2022 Guide)
If you already understand the basics about a boat battery, found in our comprehensive 2022 guide. Then it’s now time to learn how to choose a boat battery that’s best for your boat. Below are some basic things to consider before buying.
If you want to skip to a particular section, use the navigable table-of-contents. Otherwise let’s begin.
Outdoors Informed is reader supported. We independently research and rate every product. When you buy through a link on our site, we may earn an affiliate commission. However, our opinions and evaluations are our own. Outdoors Informed does not accept free products from manufacturers. Learn more.
12 Considerations To Choose A Boat Battery
First, choose what application your boat needs. Remember that “Starting” batteries deliver short bursts of juice to power the starter. Under no circumstances should you discharge these types to empty. Whereas a deep-cycle battery, tolerates deep discharges to power accessories. They can discharge and recharge many times before dying. Then there’s “dual-purpose” batteries which combine some qualities of both. This type is a compromise of each.
Next, choose which type of chemical technology you want in your marine battery. One choice is an old standby, the Wet cell battery. It provides reasonable performance at a low cost. Yet, as an unsealed battery, it can spill hazardous acid. As well, it needs hands on maintenance in the form of checking and filling the electrolyte (aka “acid”).
You could upgrade to sealed battery, the gel cell is more money, but spill proof. Alternatively, for even more money try the “Absorbed glass mat” abbreviated as an AGM battery. These offer a slow self-discharge rate and more power in a smaller footprint.
If initial cost is not a worry, try a lithium battery. These are superior to all previous types, but expensive.
For starting batteries, you want to pay attention to the “Cold cranking amps” (CCA). This is the number of deliverable amps at 0 degrees F for 30 seconds. Or look at the “Marine cranking amps” (MCA), which is the same as (CCA) but determined at 32 degrees F.
Next for deep-cycle and dual-purpose batteries, consider the “Ampere-hour” (Ah) rating. A measurement based on a 20-hours long draw of a full charged battery.
Another important consideration for battery selection is “Reserve Capacity” (RC). This is the number of minutes a full charged battery at 80 degrees F will discharge 25 amps. Until it drops below 10.5 volts and “dies.”
Batteries come with volts; most boat batteries are either 12 volts or 24 volts. The amount of volts will depend on the size of the boat and the type of equipment that needs power. Larger boats use 24 volt batteries because this type will cause less of a voltage drop on long wire runs. Pay close attention to available space on your boat. In many instances you can have a 24 volt system with ‘droppers’, instead of many 12 volt batteries. These ‘droppers’ lower the voltage to supply 12 volts for certain electronics (VHF, or GPS, etc.).
A “group” (example: 24, 27, 31, 34, 6D, 8D, etc.) refers to a battery’s physical size, all manufacturers build to group sizes. Despite some having differences in dimensions, due to handles or post height. Match the group size on the label to the physical space on your boat. Finally, keep in mind about if the battery requires a ventilation system.
Battery labels state the date of manufacture, the label denotes the month and year. Months are letters (A-Jan., B-Feb. C-Mar., etc.) and the year by numbers (ex: 1= 2011, 2=2012, etc.). For example, “C1” denotes a battery manufactured in March 2011. It’s in your best interest to buy the newest built battery.
Weight is an important factor for boater who intend to move the battery in and out of the boat every season. It makes no sense to choose a battery that pose an injury risk when handling. Choose the battery you are comfortable carrying.
Boats operate on motors, so the battery feels constant and violent vibrations. Vibration is a common cause of damage to the internal parts of most boat batteries. Vibration can cause the inner cells to dislocate which deteriorates the battery. Thus, vibration resistance batteries will last longer than the standard ones.
Before buying the battery, check the position of your battery compartment. Certain chemical types like Wet cells need to be vertical, since it’s at risk of acid spilling. Whereas, the Gel cell, AGM, and Lithium work in any position. Except upside down, as it might damage the internal parts of the battery. For battery compartments that accept positions other than horizontal it’s best to choose a sealed battery.
Flooded marine batteries need hands on maintenance. This includes checks for spills or terminal corrosion and refilling of distilled water. Many casual boaters find this type of maintenance task a nuisance. Sealed batteries (Gel, AGM, and lithium) only need external checks and cleaning. So consider how much maintenance appeals to you.
All the boat batteries offer some kind of warranty period. Some batteries come with full-rated warranty period and some come with pro-rated period. In full-rated warranty, free replacement is an option if it fails before the warranty ends. Whereas for a pro-rated, you will only get some amount refunded for the unused period of warranty. Be mindful when you review any warranty.
Many batteries are available at a wide range of budgets. If you have a budget in mind, go for the best battery that is affordable to you. Lower budget ones can be as powerful as higher budget ones but will need more maintenance.
Cautions About Life Expectancy:
Most average battery life expectancies are shorter these days due to increased energy demands onboard. Here’s a sad fact; only 27% of batteries sold today reach the 48-month mark. What’s worse is that sulfation build-up is the reason for 80% of all battery failures.
When Does Sulfation Happen?
It happens when marine batteries sit too long between charges, overtime it will sulfate. As little as 24 hours in hot weather and several days in cooler weather.
There are many causes of sulfation, such as:
Improper storage without some type of charger connected to it.
Over discharging an engine-starting battery. These types of batteries cannot stand deep discharge.
Not Charging Enough
Undercharging of a battery to only 90% of capacity. Sulfation deposits don’t break down, so they increase in size, damaging the lead plates.
Leaving Battery Out In High Temperatures
Exposing a battery to high external temperatures (100+ degrees) for long periods. Doing this will increase the natural internal discharge. A full charged battery left sitting for 24 hours a day at 105 °F for a month will result in a dead battery.
Allowing For Low Electrolyte Levels
Low electrolyte level. Flooded batteries need refilling of electrolyte. Any lead plates exposed to oxygen will start to sulfate.
Cheap Charger Use
Incorrect charging levels and settings. Most cheap marine chargers do more harm than good.
Harsh Cold Weather
Cold weather is hard on the battery. The chemistry will not create the same amount of energy as a warmer battery. A near empty battery can freeze solid in subzero temperatures.
Phantom Or Parasitic Draining
Parasitic drain, this is a load put on a battery with the power off. Ongoing parasitic draining makes for poor battery performance and short life expectancy.
Conclusion: Choose A Boat Battery Wisely
With all the information you gained in this article you should be confident to choose a boat battery. As you can read buying the right boat battery for you depends on many factors. It’s my goal for this 2022 guide of “how to choose a boat battery” to be a simple-to-follow guide. Gaining this knowledge will help you to make confident and informed buying decisions.
Thank you for allowing Outdoors Informed to help you in your research, so you can spend more time “energized” on the water.