Article by Capt. Steve Katz
Welcome to the 2017 season of Ship to Shore. As in the past, the first few articles of the season will review some topics that are helpful in getting your boat ready for the season, If there is a topic you would like covered this season, please let them know at the Coastal Fisherman.
So what is 12.65? It is the voltage of a fully charged battery. Why is this a big deal? There are not many ways for us to know the condition of a battery on-board our boat until it is too late and the battery is dead. Monitoring the battery’s voltage is the easiest and least expensive way to keep informed on the battery’s health. As an example, if your fully charged battery voltage drops down by .2 volts (2/10 of a volt) to 12.45 volts, the battery is only 75% charged. That is a big change in battery capacity with just a small amount in voltage change. Further, if your battery drops to 12.00 volts, it is only about 25% charged! While this amount of voltage may be hard to measure with traditional marine gauges, installing a precise digital voltage gauge will help you to monitor battery health. These measurements need to be taken while the battery is resting and not under any load or being charged.
Load testing is another way to measure the batteries health. Usually preformed at a battery store or automotive shop, this test puts a load on the battery and monitors the battery’s voltage to see if it can handle the load without too much of a voltage drop. There are other tests, such as modern conductance testers that measure internal resistance of the battery to determine the battery’s capacity and health.
If your battery voltage is low, often a simple recharge can get it back to full capacity. There are many different types of chargers, technologies, sizes and features of battery chargers available. Basically a charger outputs a higher voltage than the battery, causing electricity to flow from the higher voltage-charger to the lower voltage-battery. In order get a battery fully charged, it needs to be charged with a voltage of approximately 14 volts. A charging voltage too high will overheat the battery, causing the electrolyte to gas out and eventually dry out the battery. Charging with a voltage too low will not fully charge your battery.
The best way to charge a battery is with a modern multi-stage battery charger. These modern chargers have a controlled algorithm that changes the voltage and current based on time. A multistage charger starts out with a bulk charge, sending a high current, high voltage charge for a short period of time. It then switches to an absorption charge, with a high voltage but lower current for a longer time. Once the battery is fully charged it switches to a float charge, to maintain the battery at a full state of charge.
If you are buying new batteries you may wonder about the various types, such as Flooded, AGM and Gel. All of these batteries use lead and Sulfuric acid (electrolyte) to store electricity. AGM and Gel are similar since they both are a VRLA battery (valve-regulated lead-acid battery), also known as a sealed lead acid battery (SLA). An AGM battery has fiberglass mesh between the lead battery plates which absorbs and contains the electrolyte. A gel battery has silica and other agents to convert the liquid Sulfuric acid into a gel. There are advantages and disadvantages to each type of battery, with price a primary factor for many boaters. The traditional flooded or wet cell batteries are the most popular, with some that are maintaince free (electrolyte that evaporates from the battery is captured and re-enters the battery). The second most popular is the AGM that is also maintaince free and about twice the cost as a flooded battery. AGM batteries often have better performance, charge faster and can be discharged further without damage as compared to their flooded counterpart.
Deep cycle or starting battery? A starting battery or cranking battery is designed to supply a lot of power for a short period of time, whereas a deep cycle battery is designed to supply a smaller amount of power over a long period of time. Starting batteries have a large number of thin plates designed for maximum surface area allowing maximum current output, but can easily be damaged by deep discharge. Deep cycle batteries have thicker plates that deliver less peak current, but withstand frequent discharging and recharging without damage.
Many boats use a combination of types, a starting battery for the engines and a deep cycle battery for the house loads. A deep cycle, if powerful enough can be used for starting and house power.
Periodic preventative battery maintaince is always a good idea. Clean all the battery connections by removing the cables from the battery terminals and cleaning both the battery terminals and the associated cables lugs with a wire brush. Label the wires if necessary before you remove them to assure you put hem back in the correct location. Check the cable ends to be sure they are tightly crimped on the wire. If your batteries are not sealed, check the electrolyte level and add distilled water if needed.
Learning the condition of your batteries and knowing if replacement is necessary will help you have a more reliable boating season.
Captain Steve Katz is the owner of Steve’s Marine Service and holds NMEA, AMEI and NMEA2000 certificates along with ABYC Master Technician certification and factory training from many manufacturers.
