About Yacht Batteries

Yacht batteries have the primary role as a power storage device, and a the secondary is one of a buffer, that can absorb power surges and disturbances that arise during charging and discharging. There are many boating standards and recommendations for boats, so please click on the link to reference the page on boating standards. As an explainer, these are my own personally developed International Recommendations for Boat Electrical Systems that started way back in 2002 and I have continually amended these as boating systems have evolved.  

These recommendations incorporate most or even exceed the provisions in the various other recommendations and standards. They are generic recommendations and incorporate best installation practice based on decades of professional experience. Unlike official rules and standards, which don’t have context or a rationale behind the recommendation for the average boating person to understand. Even rules and standards are under constant review and amendment.   To satisfy the trolls and myriad of critics, please check and refer to your local rules and standards or recommendations as required.

Yacht Batteries Maintenance

Battery maintenance is simple and is not the tedious chore that it is often made out to be. For all battery types perform the following.

Battery Terminal Cleaning. (3-monthly). Remove battery terminals and ensure that terminal posts are clean and free of deposits. Refit and tighten terminals.

Battery Cleaning. (3-Monthly). Wipe battery casing top clean with a damp rag. Moisture and salt can allow tracking across the top to ground or negative, slowly discharging the battery. This is a common cause of flat batteries, and the mysterious but untraceable system leak.

Yacht Batteries Installation

Rule 6.1. Batteries should be installed within a separate space or compartment that is located above the maximum bilge water level, and protected from mechanical damage.

Rationale. The batteries should be installed in a lined box protected from temperature extremes. The preferred temperature range is 10°C–27°C. The box should be located as low down as possible in the vessel for weight reasons, but high enough to avoid bilge water or flooding. Sufficient natural light should be available for testing or servicing. If this is not possible, an ignition-protected light can be installed. Allow sufficient clearance to install and remove batteries. Make sure there is sufficient vertical clearance to allow hydrometer testing if flooded non sealed batteries are used.

Rule 6.2. Batteries shall not be installed adjacent to any fuel tank, fuel pipe or parts of the fuel system.

Rationale. The batteries should not be installed close to any source of ignition, such as fuel tanks and system parts such as fuel filters, separators and valves. Any leak or accumulation of fuel represents a serious hazard and so any source of ignition should be removed. 

Yacht Batteries Installation

Rule 6.3. Batteries should be installed within an enclosure, or have a tray that will contain any spills of electrolyte at all angles of heel or inversion.

Rationale. The box should be made of plastic, fiberglass or as old fashioned as it is, lead lined to prevent any acid spills contacting with wood or water. Boxes should be at least the full height of the battery so that any spills will be contained at all times. PVC battery boxes are acceptable alternatives. I have been asked what about sealed batteries? If a battery casing for any reason fractures there will be acid seepage.    

Rule 6.4. Batteries should be secured so that they do not move at any angle of heel or inversion.

Rationale. Physically secure batteries with either straps or a removable restraining rod across the top. Batteries should be prevented from movement. Insert rubber spacers around the batteries to stop any minor movements and to absorb hull vibrations. 

Yacht Batteries Connection

Rule 6.5. Battery terminals and connections shall be installed or protected against any accidental contact with metallic objects. Battery terminals should be coated with petroleum jelly or equivalent compound to prevent corrosion or interaction with electrolyte spray if they are non-sealed battery types.

Rationale. Battery box lids should be in place at all times and secured. PVC or other connection covers should be installed where accidental contact by tools or other items can cause a short circuit across the terminals. Terminals should be coated to limit the corrosive effects of acid.  Many a person has accidently shorted the terminals with a wrench. You can buy plastic clip over terminal protectors.

Yacht Batteries Gases

Rule 6.6. Battery compartments shall not contain any electrical equipment liable to cause ignition of any generated gases or vapor.

Rationale. Do not install any electrical equipment within the compartment or adjacent to batteries. This can cause the generation of sparks and cause ignition of hydrogen gas generated after battery charging. 

Rule 6.7. Where batteries are not of the sealed type, the battery compartment should have adequate ventilation to atmosphere of all generated gases.

Rationale. The area should be well ventilated and vented to atmosphere. The use of an extraction fan is rarely required but should be considered if natural convection methods will be insufficient. If a fast charging regulator device is installed, ensure that the ventilation remains sufficient to remove any generated gasses, and prevent them from accumulating. Note that even sealed batteries can vent gases under come circumstances

Yacht Batteries Connection

Rule 6.8. Where start and service batteries have an interconnecting switch for emergency power supply, the switch should be normally open.

Rationale. In dual battery systems where an emergency bridging or paralleling switch is installed, it should be always kept at the open position. Many people leave them permanently closed and experience accidental discharge of both batteries.

Rule 6.9. Start and service batteries shall be electrically separate and arranged so that service loads cannot discharge the start battery.

Rationale. In most cases the battery negatives are bridged, and a separate negative for each should be installed. This requires a separate alternator charging negative and grounding negative to the same grounding point as the other battery. Any arrangement should ensure that the starting battery could not be accidentally discharged. Where a solenoid system is used to parallel the batteries for charging, it must always open when the charging ceases.

Rule 6.10. Battery interconnection cables should have the same rating as the main start circuit cables.

Rationale. In dual battery systems the cables connecting each battery negative or positive should be rated the same as main supply cables. Many are installed in smaller cable sizes. 

Yacht batteries Loads

Rule 6.11. Equipment having high current ratings such as thrusters and windlass systems should be installed to limit the disturbances or effects on the stability of the electrical system.

Rationale. Where high current equipment can cause system disturbances such as large load surges and voltage droops, consideration should be given to installing a separate battery bank with the required characteristics to power the equipment. In practice these equipment are connected to the start battery as the engine is running at the same time and the alternator takes some of the load. Connection of thrusters and windlasses to a house battery bank can cause disturbances. Where a deck winch is installed to a house battery bank be aware that some disturbances can occur as they are short and sharp loads being applied. Where a large inverter is installed to a house battery bank, when a large AC load is switched on and the very large DC load applied to the battery, there can be a noticeable disturbance.  All about boat battery and yacht batteries installation factors.