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Useful Information about
Inverters & Battery Chargers

Battery Chargers
Selecting the right charger
Types of batteries & uses

See our selection of Battery Chargers here ... and our Inverters here ... Or, see both types here ...

Inverters take DC power (battery or solar, for example) and convert it into AC "household" power for running electronic equipment and appliances. In selecting the right size inverter:

  • Add up the power ratings of all the appliances, then buy the next larger inverter!
  • Note, however, that some appliances, such as refrigerators and microwaves, have a surge requirement. Since every appliance has its own requirements sometimes you will need to get a bigger inverter than you would otherwise think.
  • Note that the inverter isn't the only consideration when you are pondering the mysteries of startup surges. The battery must also be able to supply the surge power, and the cables must be able to supply the increased current without dropping the voltage too much.
  • Some inverter models offer built-in battery chargers.

See our selection of marine batteries and accessories here.


Battery Chargers are designed for Cuddy, Cruiser, Sailboats, Yachts and commercial/larger fishing boats. Boats in this class typically have a common ground and are set up for shore power AC, and sometimes include the use of a generator and/or an inverter on board.

  • A 12V/DC common ground system is typical for most boats, however, larger and commercial boats may be utilizing a 24V, 32V or 36V common ground DC system.
  • A Constant Current Rate of Charge Mode is used until the battery is just below float level. Once the batteries have reached this point, the charging mode changes to a Constant Voltage Mode (Trickle Charge Mode) that is used to maintain the float level of the batteries.
  • The Battery Charger must match the battery type being charged, or you risk overcharging or undercharging your batteries.


Select the correct Battery Charger for your needs.

  1. Determine what type of battery or batteries you will be charging.
    • Maintenance Free, Wet Cell (flooded), AGM (absorbed glass mat), or Gel Cell.
    • In most cases one charger will work for all except for Gel Cell. However, some of our Gel Cell chargers will work well with the other battery types.
    • Many chargers have selection switches to designate the type of battery to be charged; some allow multiple types to be charged simultaneously.
  2. What size is your battery?
    • What that means is not physical size, but how many Amp hours does your battery store.
    • Example A: a typical full size auto battery is about 50 amp hours, and it would take a 10 amp charger approximately 6 hours to recharge it if the battery were completely dead.
    • Example B: a Marine Deep Cycle Battery may be rated at 100 amp hours, so it would take a 10 amp charger about 11 hours to recharge a dead battery to near 100% full charge, from a completely dead condition.
    • As a rule of thumb, take the amp hour rating of the battery and divide by the charger rating (amps), then add about 10% for the extra time to totally top off the battery. This will give you total charge time.
    • Some folks need to size the charge for quick recharge, therefore requiring more amps from their charger. Others are not in a hurry and may select a smaller charger.
    • The most important thing here is to make sure you have enough charger power to do the job you require in the time you allocate.
  3. Know your desired outcome.
    • Some folks require a charger to keep their battery charged during the off season. In such a case a simple low current charger will work fine.
    • Others require a fast and powerful charger to quickly restore a trolling motor battery.
  4. Other factors in selecting a battery charger
    1. Input voltage,generally for use foreign countries.
    2. Exposure to elements, i.e. would you benefit from a waterproof charger?
    3. Perhaps you will need a charger that doubles as a power supply for another application.
    4. Often people will need to charge multiple batteries simultaneously, so multiple bank chargers may be needed.


List of definitions of different types of batteries and their uses:

  1. Flooded:
    • The traditional engine start and traction style battery.
    • Liquid electrolyte is free to move in the cell compartment
    • User has access to the individual cells and can add distilled water as the battery dries out.
    • Popular uses are engine starting and deep cycle designs.
    • Typical absorption voltage range 14.2 to 14.5 volts, typical float voltage range 13.2 to 13.5 volts.
  2. Sealed:
    • This term can refer to a number of different constructions, including only a slight modification to the flooded style.
    • Although user does not have access to the cell compartments, the internal structure is still basically the same as a flooded battery.
    • The only difference is that the manufacturer has ensured that a sufficient amount of acid is the battery to sustain the chemical reaction under normal use throughout the battery warranty period.
    • Other types of lead acid batteries are also sealed, as explained below. Very popular uses are engine start and limited starting/deep cycle applications.
    • Typical absorption voltage range 14.2 to 14.5 volts, typical float voltage range 13.2 to 13.5 volts.
  3. VRLA:
    • Valve Regulated Lead Acid battery - a sealed battery.
    • Valve regulating mechanism allows for a safe escape of hydrogen and oxygen gasses during charging.
    • Typical absorption voltage range 14.2 to 14.5 volts, typical float voltage range 13.2. to 13.5 volts.
  4. AGM:
    • Absorbed Glass Matt battery - a sealed battery.
    • Newer sealed battery with "Absorbed Glass Mats", or AGM between the plates. These batteries have all the advantages of gelled batteries, but can take much more abuse. These are also called "starved electrolyte" or "dry" batteries because the glass mat is only 95% saturated instead of being fully soaked, which means that they do not leak acid even if the casing is broken.
  5. GEL:
    • The gel cell is similar to the AGM style because the electrolyteis suspended, but different because technically the AGM battery is still considered to be a wet cell.
    • The electrolyte in a GEL cell has a silica additive that causes it to set up or stiffen.
    • The recharge voltages on this type of cell are lower than the other styles of lead acid battery.
    • Probably the most sensitive cell in terms of adverse reactions to over-voltage charging.
    • Gel Batteries are best used in VERY DEEP cycle applications and may last a bit longer in hot weather applications.
    • If the incorrect battery charger is used on a Gel Cell battery poor performance and premature failure is certain.
    • Typical absorption voltage range 14.0 to 14.2 volts, typical float voltage range 13.5 to 13.8 volts.
    • Note about Gel Batteries: It is very common for individuals to use the term GEL Cell when referring to sealed, maintenance free batteries, much like one would use Kleenex when referring to facial tissue or "Xerox machine" when referring to a copy machine. Be very careful when specifying a charger. More often than not, what someone thinks to be a Gel Cell is really a sealed, maintenance-free, AGM style battery.


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