A boat’s battery bank is at the heart of its DC electrical system and the bank’s state of charge (SOC) is critical information. Not only is it important to know how much energy remains stored so you do not deplete the bank and no longer have the power needed to run ship’s services, but it is also necessary information to maintain the batteries in good health to maximize the number of cycles possible from the bank of batteries.
A voltage meter can provide an estimate of the bank’s SOC, but an analog meter will only provide a rough estimate. Even a digital voltage meter is not able to give wholly accurate information. A dedicated battery monitor will not only provide voltage readings and the battery bank’s state of charge, but it can also display real time amperage flow, an estimate of time the present draw can be sustained before depleting the stored energy.
The battery bank’s state of charge can typically be displayed in both as amp hours or as a percentage of charge remaining. Many monitors are “self-learning”, which allows the monitor to compensate for inevitable electrical inefficiencies when charging. They can also re-calibrate to ensure that the SOC is at 100% when the batteries are fully charged, and thereby improving the accuracy at all points of the charge/discharge cycle.
– Lyle, PYS Marine Electrical Technician