Secrets of A Marine Battery Charger Revealed

Secrets of A Marine Battery Charger Revealed

Marine battery chargers are typically designed for a ‘marine’ environment but, their design may be little different from non-marine chargers. Conocer The key factor in your choice of a marine battery charger is its planned usage or application. Marine batteries are usually not much different from non-marine batteries except that they may be more likely to be deep cycle, deep cycle and starting, lead acid, or sealed lead acid. They also may be constructed with materials which resist corrosion and have vibration dampening materials between the plates. Marine battery chargers don’t care about their environment, rather they are designed to distinguish between battery chemistry (flooded, gel cel, AGM – absorbed glass mat).

Here are the most important considerations when choosing a marine environment battery charger:

1. Charger Environment


If your boat is open and exposed to the elements, you should choose a charger with a waterproof housing. When considering waterproofing, a specification to look for is ingress protection rating. An ingress protection rating of IP68 would be totally dust tight and provide protection against prolonged effects of immersion in water under pressure. These units are usually fully sealed, safe to store onboard year round, and can be permanently left in a damp environment. They may be described as fully potted which means that the electronics are encapsulated in resin.

Your boat application may not require a waterproof housing. If your boat is large with an enclosed cabin, where you can insure no direct contact with water, you may choose a battery charger that is not waterproof.


If your battery’s environment experiences prolonged, significant vibration, you should look for a vibration proof specification for the any unit you are considering. Vibration can be handled through a rugged case or through vibration dampening materials used in construction.


If your environment experiences frequent or severe temperature changes, you should choose a battery charger that compensates for temperature changes. This is important to insure the proper charging and maintenance of your battery.

2. Charger Output

Charger output can be described in two ways; amps and banks.

The amps or power output of the charger should again be determined by applications.

a. Low Output – (6 amps or below) A low output charger may be applicable for maintenance use or any low amp hour battery application.
b. Medium Output – (9 – 15 amps) A medium output charger would be applicable for medium use or occasional use perhaps only on weekends for a trolling motor.
c. High Output – (15 amps or above) 1) A high output charger would be used in high amp hour battery applications (150 ah for example) or any situation where repeated rapid recharges are called for.

Banks (physical outputs) determine how many batteries can be charged simultaneously by the battery charger. Single banks are used for a single battery while multiple banks can be used to charge and maintain 2, 3 or more batteries simultaneously. A key specification for multiple bank chargers is whether it has independent outputs (a separate positive and negative connection per bank) and each bank has its own microprocessor to control charging. Independent outputs allow batteries of different size, type, and charge status to be connected simultaneously to the same battery charger.

3. Battery Chemistry

Batteries used in marine applications may be more likely to be deep cycle, flooded, Gel Cel or AGM. It’s important to determine your battery’s chemistry and carefully select a unit that supports that chemistry. Particularly in the case of Gel Cel batteries, it’s important to make sure your battery charger is a true gel cel charger. Some chargers that claim to be gel cel chargers are only AGM or deep cycle.

4. Ignition Protection

Because of the enclosed nature of some marine engine and battery locations, it’s important that you check for an ignition protection feature. Ignition protection keeps sparks out when starting the engine preventing the ignition of surrounding flammable gases. Check for compliance with ISO 8846 and U.S. Coast Guard Title 33 CFR 183.410 ignition protection specifications. These specifications insure:

a) the device will not ignite a flammable hydrocarbon mixture surrounding the device when and ignition source causes an internal explosion
b) or is not capable of releasing sufficient electrical or thermal energy to ignite a hydrocarbon mixture
c) or the source of the ignition if hermetically sealed.

5. Power Supply

Some battery chargers can provide power inversion to allow them to be used to power AC devices on your boat. They can also provide converted voltage to charge various DC devices. If that is important to you, make sure you choose a charger with this capability.

6. Onboard

Onboard battery chargers can be mounted to your boat permanently using a bracket. This makes them immediately accessible each time you need to charge your battery and is more convenient for leaving the battery charger in maintenance mode full time.

7. Starting

Some battery chargers can also provide enough amperage for starting in the case where your battery is too weak to start the engine of your boat. If you need that capability, be sure your choice of unit has starting amperage.

8. Warranty

All other features and specifications being equal, choose the best warranty you can find. It is not uncommon for battery chargers to fail, particularly in marine environments. Make sure your manufacturer backs its equipment with a solid warranty. A two plus year warrant should be expected.

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