Battery technology has gone a long way, so much so that there are now different kinds of batteries for every particular purpose. For instance, there are now batteries expressly made for cars and batteries for exclusive boat use. Generally, a boat battery is a lead-acid battery which is not the same as the conventional lead-acid battery for cars. It Could either be an AGM, flooded, deep cycling battery, although the lithium-based battery is slowly gaining acceptance as a marine battery.
Since most of us use boats for pleasure, we want to be able to enjoy a day out in the lake or in the open sea trouble-free. The choice of the right kind of battery will go a long way to make this possible. But, if you are unfortunate enough to have a dead battery in the middle of a trolling expedition, you should at least know how to charge a boat battery in the water.
Charging Boat Battery in the Water
Before going to the how to let’s first go to the what. What type of charger do you need to charge a boat battery? Your car battery charger just won’t do. Boat batteries’ response to charging is different from car batteries, and different kinds of boat batteries respond to charging differently. And the key to successfully and speedily charge your boat is the right charger. That should correspond to the type of your boat battery.
For instance, an AGM boat battery can be charged with a traditional charger that is meant to deter overcharging; thus you can charge worry-free while you continue to cast your line out on the lake. Meanwhile, charging a deep cycle boat battery requires cycling the battery moderately.
Types of boat battery charger
As already mentioned above, a regular car battery charger is not a suitable charger for your expensive boat battery. Some of these chargers, particularly the cheaper ones, are not capable of shutting down completely that it needs monitoring to avoid overcharging. And most importantly, using an inexpensive charger with inadequate charging efficiency could curtail the life of your battery.
So, for charging boat batteries, two types of chargers are available; onboard and portable.
Portable boat battery charger
A portable battery charger is the type used when the battery is out of the boat. Although not as expensive as an onboard charger, it suffers from some disadvantages, mainly, being quite inconvenient to attach and transfer from battery to battery in the restricted room or space of the battery compartment of a boat. Also, since they are movable, there is always the risk of it being stolen, especially when you are using it in a public place.
Onboard boat battery charger
An onboard charger is wired into your boat battery system, and therefore much more convenient to use, although a bit more expensive than a portable charger. All you need to do is plug it into a 120-volt outlet. And since it is securely installed, there is very little danger that it will be stolen.
But, one important advantage of an onboard boat battery charger is its advanced technology that allows the desired multi-stage switching in charging a boat battery. That’s why the preferred charger by most boat owners is a smart multi-stage onboard boat battery charger.
A smart multi-stage onboard boat battery charger is meant to deliver fuller and faster charge, which eventually mean higher available capacity, longer life, and less loss of electrolyte (for wet batteries) for your battery. Using a smart multi-stage charger also lessens the risk of over-charging and destroying sealed batteries.
Advanced battery charging technology depends on microprocessors or computer chips to deliver the right amount of volts and amperes on a regulated basis, and this is achieved in three stages; bulk, absorption, and float by what is called a “smart charger.”
In the bulk stage, which delivers 75%-80% of the charge, the charger supplies the maximum current it can safely deliver at a consistent rate as the battery voltage increases. The amperage could be from 10% to 25% of the capacity of the battery in AH (ampere-hours). With a wet battery, the temperature should not increase to more than 125° F, while on a valve regulated or AGM battery, more than 100° F
The absorption stage is that point when the voltage is already stable, but the amperage is slowly reduced and controlled while the battery is being topped-off. This roughly comprises the residual 20% to 25% of the charge. At this stage, the battery should be registering around 14.1 volts to 14.8 volts. A “set point” in the charger changes the current accurately for the voltage to remain constant, at say 14.4 volts, as the battery takes in the required energy to attain full charge status. If not, over or under-charging could occur.
Float stage is that point where the voltage is just adequate to prevent the battery from losing charge. At the float stage, the charging current dips to almost zero, allowing the voltage of the battery to fall to around 13.5 to 13.8 volts. What is good about this is that while on “float mode” the battery can be on a fully charged state indefinitely.
How to charge a boat battery
Now that you have the right charger for your boat battery, charging it is quite easy and simple.
Step 1 – Inspect the battery
Check your battery for dirt and debris before you start the charging process. Make sure that the switch is in the off position when you do the cleaning. Inspect the battery connectors and terminals also for corrosion and dirt and clean it.
Step 2 – Connect the charger to the battery
Once you’re sure that the battery is clean, you can start the charging process. First, you connect the battery charger to the battery’s terminals. ( we are assuming here that you are using a smart onboard boat battery charger).
Step 3 – Charge the battery
Charging starts once you switch on the smart battery charger and it will do its work. You can check the progress of the charging as it goes from bulk, absorb and float stages from the LED display on the charger.
Step 4 – The end of the charge
As soon as the battery is fully charged, switch off the charger and disconnect the charger from the battery terminals.
Now that you’ve successfully charged your boat battery, you can now proceed with what you intended to do, relax and enjoy as you contemplate the next catch!