The basics of batteries and battery monitoring

All electronics on board på a boat needs power, and usually this comes from a battery. However, each ship will have different battery requirements depending on; the amount of current needed, the size of the the ship, etc... Some boats will have multiple batteries, while others may only have one.

Types of Battery
There are a number of different types of batteries, but most are all based on same lead-acid chemistry, where the battery contains lead plates, lead oxide plates and sulfuric acid (electrolyte).

• Water cell battery: A battery where the plates are immersed in sulfuric acid.
• Absorbed glass mat (AGM) battery: The sulfuric acid is absorbed in fiberglass mats placed between each plate.
• "Gelified" Electrolyte Lead Acid (GEL) cell battery: The sulfuric acid ix is ​​mixed with fumed silica to create the gel-like substance.

There are other types of battery chemistry available at market, but since these are the most common 3, we have covered them above.

It is important not to mix battery types if more than one battery is required, and they should be placed in the same surrounding environment; if they are from the same battery bank.

What is a battery bank?
A battery bank is where more than one battery is used on same place. It is common for larger ships to have several battery banks, while others use smaller banks but they are larger in size.

An example of; a typical battery bank installation can bestå of 3 banks, one of which is the "house bank", which supplies power to the built-in electronics, for example your on-board light.

The other 'engine bank' is for the engines and generators, and the third is an 'emergency bank', which is for the critical systems to Make sure they never go out, which is when your AIS, VHF, etc would be powered from them.

Mounting the battery
All batteries should be mounted on a safe and dry but easily accessible place if maintenance is needed. The mounting location should have a built-in valve nearby, on because the water cell batteries discharge hydrogen gas.

In addition to this, the battery should not be mounted above or below anything related to the fuel system, such as; like fuel tanks or filters (for obvious reasons!), and realistically it shouldn't move at all when mounted. There is a maximum freedom of movement on; 1" but no movement is preferable and safer.

Connect the battery
The thickness of the wire (American Wire Gauge (AWG)) Depends on the electronic load and battery power on the vessel, plus according to local wiring specifications.

If 6AWG and larger wire is used before they are connected to the battery with wing nuts, and there should be a maximum of 4 wires per battery post.

As part of the NMEA standards; all bare wires must be tinned, and multiple wires connected to a battery must be installed with the highest amperage closest to the battery.

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