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Words and pictures by Greg O’Donoghue.

Battery charging and management. In our May issue we introduced you to the different battery types on offer. Now that you know what battery to buy, it’s time to learn how to charge and manage them properly.


Hopefully, the first article Power Source illustrated the importance of selecting the right horse for the course. Now that you’ve calculated your daily demand and decided on the correct battery for your application, you need to think about charging and managing your battery bank. For convenience, we’ll consider a 12 V service bank. If your service bank happens to be 24 V, just double the voltage we refer to and you’ll get the same result. Once you’ve found that perfect spot and set up camp, your 12 V equipment will be using amps from your service battery. The average amp draw, multiplied by the number of hours you consume before charging, gives you your consumed amp hours. Once you’ve reached your desired depth of discharge, these consumed amp hours need to be returned to the batteries. This can be achieved by using one charge source, or a combination of charge sources.

Ideally, batteries should be charged at a high voltage for a set period of time, after which the voltage must be reduced to below approximately 13.8 V, at which constant level the batteries can be maintained indefinitely. You may recall that in the first article we spoke of gassing voltage. In essence, you should keep a battery below this gassing voltage of 14 V at 20° C for extended periods. Most smart battery chargers or regulators are three or three-plus stage chargers/regulators. This method of charging ensures a quick and safe charge cycle that will extend the life of the battery.

The first stage is usually a bulk charge, in which the maximum current available is delivered to the batteries until the bulk voltage (14.5 to 14.7 V) is reached. This bulk voltage is maintained for one or two hours. The charger/regulator then steps to absorption mode, at about 0.2 V below bulk voltage. The absorption voltage is held for approximately four hours, while the batteries absorb current. After these steps, the charger/regulator steps to float (13.2 to 13.8 V), at which level the batteries can remain connected indefinitely.

All the voltages referred to here are dependent on battery type and ambient temperature. Please refer to the battery supplier’s guide for the correct settings…

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