[Grei R. S. Walker]

Automotive starting batteries are made for starting engines, with the quick release of a big burst of power. They discharge only about five percent, and are intended to be immediately recharged by the alternator. They cannot handle the repeated deep discharges typical of marine use and they may suffer damage from the constant pounding they receive at sea. Conventional wet (lead acid) deep cycle batteries or deep-cycle gel cells or AGM batteries are best at withstanding the deep discharges, rapid high power recharging, and the physical pounding of the marine environment. Look for batteries with the greatest number of life cycles at 50% discharge and do not mix batteries of different construction type (such as, for example, wetted lead acid and AGM) in the same bank - use one or the other. There are also dual purpose batteries claimed to provide relatively high engine starting power for their size but also relatively good deep cycling capability. (Don't count on these for cruising with repeated heavy deep cycling.)

[cstacynicholsonj]

Many boats charge their batteries with an engine-driven alternator. If your engine running time is minimal, you want to charge as quickly as possible, without damaging the battery. Battery damage begins when the internal temperature becomes too high, causing it to gas and heat up. If it feels warm to the touch or if you're smelling gas, it's getting too hot. A smart voltage regulator for the alternator should control and taper off the charge to prevent this and can also be set, within limitations, to accommodate your needs. More on this below. more

[Vladimir]

Many people also use wind generators and solar cells to keep their 12 volt system charged. Solar cells generally have less output for the money than wind generators and require special mounting racks or cabin or bimini top space. Wind generators can usually put out more current, but only if the wind is up. They make noise, which some find objectionable but others find soothing. Usually people become accustomed to it. Great care must be taken to avoid being hit by a propeller and also to shut it down when the wind gets too high. Better wind generators have a self contained automatic dampening mechanism to prevent over-speed in high winds. One or both systems are often used by those who don't consume much electricity or who want to keep their batteries up while they're off the boat, particularly as when there's no dock power available as when they're at anchor or on a mooring. Even with these systems you must provide overcharge protection. Devices that do this usually come with the wind generator or solar cell.

[Galuel]

With multiple battery banks many people prefer to have a device which automatically shifts charging output to different banks so that no one bank is overcharged. However many prefer to monitor bank status manually and use a battery selector switch to direct charging current to the appropriate bank. Failure of automatic devices, often hidden away in an engine space, can result in improper charging leading to discharge or overcharge which will "cook" a battery, ruining it, and which could cause explosion or emission of large amounts of corrosive explosive gas.

[qbgtrfv]

If you are on a personal connection, like at home, you can run an anti-virus scan on your device to make sure it is not infected with malware.

[cheapvps]

If you are at an office or shared network, you can ask the network administrator to run a scan across the network looking for misconfigured or infected devices. more

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[drwhite]

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[carolinetimms2]

With current flowing toward the battery, voltage should read 14.8 volts or higher, depending upon the parameters of the voltage regulator. If you see no increase in voltage from your static battery test level, the alternator or regulator is not performing properly. Before condemning these expensive parts, however, troubleshoot further.

[panichelper52]

PROBLEM DIAGNOSIS

It's usually easy to know when the charging system isn't generating enough power -- just look at the warning light or gauge. If the light or gauge is not working, the battery will discharge to alert you of a potential problem. The charging system should also be checked if the engine cranks slowly or if dim headlights brighten upon acceleration.

[Klintel]

BELT MAINTENANCE

It is very important to regularly check the alternator drive belt; this can be done whenever the cooling system is serviced. Check the belt tension using a belt tension gauge. And while both "new" and "old" belt tension specs are provided in your service manual, keep in mind that a belt is considered old after just 10 minutes of use! If you do not have a belt tension gauge, press down on the belt with your thumb midway between the two pulleys. If it deflects more than 1/2", it is too loose.

[Galuel]

ADVANCED BATTERY CHECK

There are several ways to test a battery to see how good it is. The quickest and easiest is the load test. A predetermined load is placed across the battery terminals and held for ten seconds. At the end of the ten seconds the voltage across the terminals is measured and this voltage determines how good the battery is. If the voltage stays above 11 volts, the battery is good and healthy. If the voltage drops between 9 and 11 volts, the battery is determined to be borderline. It will be okay in warm weather, but may fail as the temperature drops toward freezing. If the voltage drops below 9 volts, it's no good. [links]

[nrtr]

If starter and alternator circuits check okay and the battery's cells read normal specific gravity at a full charge (applicable for open-cell batteries), the chronic low battery voltage is still possible. Accessories like the clock or the improper hook-up of an aftermarket sound system can cause the battery to go dead. (Be sure to wire you sound system through a fused and ignition-switched accessories (ACC) source.)

[Andreas Schildbach]

Drop-In batteries are most often sold in standard lead acid case sizes eg: Group 27, 31, 4D, 8D etc.. One of the drawbacks to a drop-in battery is that most of them lack any external communication between the internal sealed BMS and the vessel. Currently the 315Ah Lithionics GTX12V315A is the only drop-in marketed battery that offers external communication between charge sources and the battery.
more

[paulkeogh]

#2 – If you intend to move forward with a Li-Ion based bank please check with your insurer first. I am now receiving emails from readers who have been told they can’t have any Lithium-Ion chemistry banks, including LiFePO4.

[chadwick7cohen]

#3 Internal Wiring – It is not uncommon to open a 100Ah drop-in battery, rated at 1C, and find a single 10GA or 12GA wire feeding the main positive and negative terminals. When someone finds a 10GA or 12GA wire rated for 100A, under any safety standard, please let me know? here

[alenmatias]

The base of this article was written a number of years ago (2010) but this does not mean the information here is outdated. I have been keeping it updated and have added to it when ever I have time. Last edit was 3/13/2021.