How to choose the right marine battery？

How to choose the right marine battery？We all have serious need for electricity onboard and a good working battery is one of the most important crew members. It’s not encouraging, yet it’s a fact: batteries degrade over time. At some point, you shall be looking forward to buying a new one. It’s important that you choose the right battery for your boat.

But … which is the right one? It’s very difficult to select as there are countless choices. The most important factor that you must consider is the purpose of the battery. Do you require a battery only for starting the boat or also for running the various power-hungry electronics onboard? Or perhaps both.

According to the demand of usage, basically there are three types of marine batteries:

l  cranking battery,

l  deep cycle battery,

l  dual purpose battery.

Other basic considerations before purchasing a new battery are:

l  battery capacity (Ah rating),

l  battery group, i. e. battery’s physical size (make sure the battery perfectly fits in the battery box),

l  weight (choose the battery with average weight to be able to move it in and out),

l  output (marine cranking amp rating, reserve capacity rating, cold cranking amp rating),

l  technology (flooded, gel, AGM, lithium-ion; gel and AGM are maintenance-free sealed batteries),

l  warranty.

l  manual

Cranking or starting marine battery

These types of batteries offer high bursts of power for short periods of time to kick over your engine and power your boat. The cranking battery sends power to the engine when the ignition switch is activated. Starting batteries are intended to put out a large amount of current for a short period of time. A cranking battery has more number of lead plates that are thinner and with more surface area to provide the necessary power.

Power or deep cycle marine battery

The deep cycle battery is designed to supply steady power over an extended period — like those commonly used in marine vehicles. It’s why this battery is sometimes called a marine battery.

It’s pretty different from the car starter battery, which delivers large amounts of power in a short burst and is recharged by the alternator.

The term “deep cycle” is traditionally used with lead acid batteries to contrast it from lead acid starter batteries. It refers to the ability to discharge most of its capacity (have a deep discharge) before needing a recharge.

How are deep cycle and starter batteries different?

In lead acid batteries, the main difference between a deep cycle and a starter battery is structural. Deep cycle batteries have thicker plates with more dense active material and thicker separators. The thicker battery plates resist corrosion through extended charging cycles.

Dual purpose or hybrid marine battery

It’s a hybrid battery that has been designed in a way it can be used as both cranking and deep cycle. Dual purpose batteries are sort of a blend of properties of the two. Like many 2-in-1 options, they do not always allow your boat to perform at the same level as two batteries would. When purchasing a new battery, don’t forget to recycle your old one. Lead acid batteries can be safely completely recycled when done properly in the right facilities.

Battery monitor is your battery’s best friend

Battery Monitors primary function is to act as a FUEL GAUGE for energy stored in the battery system providing its state of charge. e Marine Systems offers a variety of battery monitors for your land, mobile or marine energy storage..

How does a battery monitor work?

Battery monitors work by means of a shunt installed between the negative post of the battery bank and the “load” (that is, all of the electrical devices). For one to correctly track amps in and out, nothing can be connected directly to the negative side of the battery bank other than the shunt.

Monitoring Battery Capacity

Keeping accurate track of battery state of charge is essential for the high performance marine electrical system. Today’s expensive heavy duty batteries are too valuable to leave without proper monitoring. Traditional ways of assessing state of charge don’t always work with these batteries and more sophisticated measuring systems are now available at relatively low cost compared to the cost of the batteries they are looking after. It makes good economic sense to upgrade to a modern metering system.

Using a hydrometer to measure state of charge for wet cell batteries

Hydrometer With wet cell batteries the most accurate determination of the state of charge is with a hydrometer. The hydrometer determines the amount of sulphuric acid in the electrolyte which translates to the state of charge of the battery. Because this concentration varies with temperature the measurement has to be carried out at the standard temperature of 80 degrees F or calculations have to be made to correct the reading to the actual temperature. A fully charged cell has a specific gravity of around 1.27 to 1.28 depending on the battery manufacturer. A discharged cell will have a specific gravity of about 1.1 To be fully accurate the battery has to have been at rest for a period of 24 hours before the reading is takes to ensure homogeneity of the electrolyte.

Using a voltmeter to measure state of charge

VoltmeterA voltmeter can be used to get a quick snapshot of the state of charge of any battery type. A fully charged 12 volt battery will have an open circuit voltage of around 12.6 volts depending on the type, and a battery is considered fully discharged when the voltage drops to 10.5 volts at the 20 hour discharge rate. A 50% state of charge is around 12.2 volts. The problem with using a voltmeter to measure state of charge is that the battery has to be at rest for 24 hours to get an accurate reading. This precludes using the method for day to day operations.

Using an impedance based meter to measure state of charge

When this article was first written this option wasn't available, but now we have the Balmar Smart Gauge and assess its success at measuring battery capacity. It measures battery impedance and by referring to stored data uses the impedance to produce a reading of how full the battery is. It just displays battery voltage and percentage charged. It doesn't show amps or amp hours. Hookup is extremely easy, just two wires attach to the battery.

Why is it important to be so accurate in monitoring batteries

The life of a battery is determined by the number of cycles it has to perform and the depth of the discharge. In general the optimum life to utility ratio will occur if the battery is not discharged lower than 50%. With an expensive battery bank it is worth spending some money on monitoring to prevent excessive discharge and premature battery failure. The only effective way to do this is with an amp hour meter. When charging batteries the top 20% of charge will normally go too slowly to be worth running an engine for.

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DEEP CYCLE BATTERIES With BMS（lifepo4 Lithium Battery）

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