Onboard Power Supply Systems

Polar DC Generators come standard with 2 DC Outputs

There are various ways to supply onboard power to a marine vessel depending on the specific application and usage demands. This page provides an overview of the various types of installations as well as their advantages and disadvantages.

48-320 Vdc Onboard Hybrid Power

10/10 EFFICIENCY

10/10 RELIABILITY

Choosing the Correct Batteries

Batteries are the most important component of an onboard power system – your safety and pleasure will be enhanced with the selection of the right battery.

Many boats use an automotive style for starting their engine and this is a good choice. Using the same style battery to store energy to operate the appliances is not a good choice, even if the battery is marked “Marine Heavy Duty”. Many boats will use a large quantity of these automotive style/marine heavy duty batteries in parallel to overcome their poor performance. Unfortunately, this worsens the situation.

Unless your need is for a very small energy storage capacity, its best to avoid 12V automotive style batteries. Best practice is to use the taller and heavier duty 6 volt or the individual 2V–3.2V battery cells. There are many good and bad batteries to choose from including: flooded lead acid golf cart style battery, the newer sealed AGM, starved electrolyte, or VRL type batteries. If you’re budget allows, lithium-ion batteries offer the best performance.

Please note that some of the high-tech sealed batteries have very poor performance parameters, especially those used in UPS systems and telecommunications. These batteries are designed for long life without cycling.

There are lithium-ion battery kits on the market supplied without cell equalizers or other electronics to manage individual cell temperatures and voltages – make sure your battery pack incorporate these features. Polar Power is supplying Lithium-ion kits that are monitored and controlled through our BMS.

24 Vdc Onboard Power with DC Generator

8/10 EFFICIENCY

10/10 RELIABILITY

A pure 24 Vdc power system has the following advantages:

Wire gauge sizes can be reduced by 1/2, saving considerable weight and cost.
Starters for the generator and propulsion engine are more robust and reliable.
Motors used for winches, autopilot, water maker, bow thrusters are more durable and better performing.

12/24 Vdc Onboard Power with DC Generator

8/10 EFFICIENCY

8/10 RELIABILITY

Using a 12/24 Vdc system has the following advantages:

The 24V battery bank is more efficient in providing power to the inverter and this will allow longer operation on the battery before recharging.
Inverters produce electrical noise on the electrical bus; and having 2 separate electrical buses allows the more sensitive communications and navigation electronics to be powered by clean 12V electrical buss. Other noise producing appliances such as refrigeration, radar, and winches can be powered off the 24V buss.
Wire gauge size to 24V appliances can be reduced in size and voltage drops minimized. Electric motor performance on winches will be enhanced.
The 24V battery bank will last longer than the 12V battery bank.
The DC generator is more efficient at 24V and higher voltages.
Battery technology is improving and costs for high-performance batteries are dropping. Having a 24V or higher voltage generator provides more efficient power for rapid charging the new battery technologies.

12 Vdc Onboard Power with DC Generator

5/10 EFFICIENCY

5/10 RELIABILITY

The advantages of using a DC generator:

Generator runtime is significantly reduced for comparable charge.
A DC generator is smaller and lighter than a comparable AC generator.
Less fuel is used in charging the battery.

The disadvantages of an all 12V system include:

Safety is reduced due to heavy currents flowing through terminals and wired connections. At high currents even a little bit of resistance (due to corrosion) can generate temperatures high enough to melt copper, this can create a fire hazard.
Efficiency in the DC to AC inverter is greatly reduced because the transistors experience higher power losses due to the higher current levels.
Battery life decreases as the number of cells (batteries) are charged in parallel. Charging in cells in series helps ensure that each cell charged equally. Battery banks at 24V and higher reduces the number of cells in parallel to achieve banks of desired watt hour capacity.
System cost and vessel weight are increased because copper wires of larger gauge size are required to handle the current.
Larger battery banks are required in 12V systems as opposed to 24V systems. A 12V battery bank is less efficient in operating an inverter and therefore has to increase in size.
Motors for winches, anchors, autopilot, desalinization and other are less efficient at 12V. As the battery drops in voltage the motor performance dies off.

12 Vdc Onboard Power with AC Generator

2.5/10 EFFICIENCY

5/10 RELIABILITY

The disadvantages of using an AC generator:

The AC generator takes longer to charge the battery due to current limits in the inverter or battery charger. Adding additional inverters or battery chargers increases system cost and takes up space while adding weight.
The conversion of AC to DC consumes more fuel due to power conversion losses in the inverter or battery charger.
The AC generator is significantly larger and heavier than the DC generator.