Charger Basics

Here are some simple steps to aide you in selecting the correct charger for your needs. (remember battery technology is changing all the time, what may have been appropriate 2 yrs ago may no longer apply today -we endeavour to keep our information up-to-date, and we also welcome feedback to our advice)

Step 1 

Determine what type of battery or batteries you will be charging. Maintenance Free, Wet Cell (flooded), AGM (absorbed glass mat), Gel Cell or VRLA (valve regulated lead acid). 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.

Step 2

What size is your battery? What that means is not physical size, but how many Amp hours does your battery store. As an example, 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. Another example, 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) and then add about 10% for the extra time to totally top off the battery, This will give you total charge time.
Some people 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.

The General rule of thumb for a "safe" charging level is to have the charger producing a current which is 10% of the capacity of the battery (rated in a/h) or 1% of the CCA (Cold Cranking Amps) of a battery. EG a deep cycling battery at 100a/h =10amp charging, a starting battery at 600CCA =6amp charging. This does not mean any type of charger, please read previous info for battery types and read on for more info

Step 3

Know your desired outcome. Some people require a charger to keep their motorcycle, classic car, or aircraft 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 or a wheel chair battery set.

There are certainly other factors in selecting a battery charger, and it would be difficult to cover them all, but here are a few. Input voltage, generally for use in foreign countries. Exposure to elements, i.e. would you benefit from a waterproof charger? Perhaps you will need a charger that doubles as a power supply for an RV or some other application. Often people will need to charge multiple batteries simultaneously, so multiple bank chargers may be needed. Calcium batteries require chargers that can charge at slightly higher voltages.

Following is a list of definitions of different types of batteries and their uses. 



Flooded: This is the traditional engine start and traction style battery. The liquid electrolyte is free to move in the cell compartment. The user has access to the individual cells and can add distilled water as the battery dries out. Popular uses are engine starting and some deep cycle designs.
Typical absorption voltage range 14.2 to 14.5 volts, typical float voltage range 13.2 to 13.5 volts. Different Plate compounds such as Calcium, Silver absorption range must fluctuate between 14.8v and can go as high as 16v, different plate construction will determine this such as expanded grid technology.

Sealed: This term can refer to a number of different constructions, including only a slight modification to the flooded style. In that case, even though the 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 in 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, such as marine and motorhome use. 
Typical absorption voltage range 14.2 to 14.5 volts, typical float voltage range 13.2 to 13.5 volts.

Calcium and Silver Alloys: Charging rates must exceed 14.8v up to a max of 16v during the charging process to successfully charge these batteries.


VRLA: This stands for Valve Regulated Lead Acid battery. This is also a sealed battery. The valve regulating mechanism allows for a safe escape of hydrogen and oxygen gasses during charging. Popular uses are Golf trundlers and mobility scooters and also kon-tiki fishing rigs.
Typical absorption voltage range 14.2 to 14.5 volts, typical float voltage range 13.2 to 13.5 volts.


AGM: The Absorbed Glass Matt construction allows the electrolyte to be suspended in close proximity with the plates active material. In theory, this enhances both the discharge and recharge efficiency. Actually, the AGM batteries are a variant of Sealed VRLA batteries. Popular usage high performance engine starting, power sports, deep cycle, solar and storage battery.
Typical absorption voltage range 14.4 to 15.0 volts, typical float voltage range 13.2 to 13.8 volts.


GEL: The gel cell is similar to the AGM style because the electrolyte is 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. This is probably the most sensitive cell in terms of adverse reactions to over-voltage charging. Gel Batteries are best used in VERY DEEP cycle application 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, VRLA or probably AGM style battery.