The battery charging requirements for the domestic, deep cycle batteries found on most boats differ, depending on the type and capacity of the battery.
Using the correct charger for your deep cycle batteries will prolong its life, keep it fully charged and take much of the guesswork out of battery charging.
The correct charger will depend on the type and capacity of your battery.
Not all chargers will be right for all types.
Also, having a battery maintenance routine can help prolong all your batteries.
They require cycled charging and re-charging for the battery to reach its maximum capacity.So, you preferably need a charger that will perform a multiple re-charging processes, unlike the single stage charge of a normal automotive charger.
Some of the lower priced ones have to be started and stopped manually and unhooked when not in use.
The chargers also come in many sizes, to suit the battery's capacity, for banks of batteries you will need a multiple bank type charger.
If you have paid a lot of money for your batteries it will be worth while investing a bit more and fitting a Smart Charger.
A smart charger monitors the battery and controls the charging voltages and currents needed to provide a complete charge and many will also equalize the charge in the individual battery cells.
There are four main types of deep cycle battery.
The most common type is the Wet Cell battery.
This is the one most likely to be bought off the shelf.
The AGM (Absorbed Glass Mat) type is similar except that the electrolyte is contained in a woven mesh which keeps it in constant contact with the plates.
They are usually sealed and regarded as maintenance free.
The VRLA (Valve Regulated Lead Acid) type is another sealed 'maintenance free' type.
This type has an internal valve to allow gases to vent..
All the above three can use the same type of charger.
The fourth type of battery is the Gel Cell.
These use a thickening agent to 'gel' the electrolyte so it doesn't slop around.
As with other deep cycle batteries they are designed for extended cycle times but also require longer recharging times.
However, the gel cell type is also susceptible to damage from over or incorrect charging.
So, using a 'smart charger' is the best option for this type.
Whatever type of battery you have on a boat is should be secured in a vented battery box.
This will protect it and the connections from any movement.
While it is good practice to coat the terminals with a thin layer of grease, you should also give them a regular clean.
Any build up of oxidation on the terminals will result in a voltage drop.
If you don't have a 'smart charger' an occasional extended charging with a lower electric voltage will help to equalize the charge in the individual cells.
And of course check all electrical connections for tightness and corrosion.
See What Others Have Posted
Battery Isolation Switch
Can you help me, I need to rewire the battery and I would like to fit an isolation switch. Is there a basic wiring diagram available for this?