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My Navigation Computer (and related accessories) shut down and/or 'freeze' when the engines are started on my vessel.

Created: 12/12/2003
Modified: 06/05/2007


Minimum Power Requirements
The Maptech Navigation Computer (sold as "Sea Ray Navigator" or "i3 Navigator") is a specialized computer designed for the rigors of the harsh marine environment. However like all electronic devices it has a set of power requirements that must be met in order for it to operate. The supplied voltage must be within a certain range, and the required amount of current must be available. Accessories attached to the Navigation Computer (such as WxWorx XM weather, radar units, and other devices) also have a set of power requirements.

The Navigation computer is designed to operate over a voltage range of 8 to 40 volts DC, and includes protection against over and under voltage. When the Navigation Computer is on, and the voltage drops below 8 volts, the computer will automatically shut off so to protect its internal circuits from damage. Accessories will also behave in this fashion, although their minimum voltage varies depending on the accessory. For example, radar will shut off or restart when its supply voltage drops below 10.2 volts. Such a voltage drop sometimes occurs when the engines on vessels are started - the power required to "crank" the engine exceeds the capacity of the battery when the additional load of the marine electronics is added. This is the same thing that occurs in an automobile; when starting the engine, the radio drops out.

Unlike the car radio (whose electronics are far simpler than those found in a Navigation Computer) the Navigation Computer must restart using its normal boot-up procedure. This also involves self-tests to ensure the computer is working properly and was not adversely effected by the sudden loss of power. This is why some electronics on the vessel may not appear to have been affected by the power loss; in fact, they do shut down and restart much quicker than a computer.

Supplying Necessary Power
There are many ways that such a shut down can be prevented - depending on how the vessel is wired.

First (and easiest) is to start the engines before powering on the circuits for the navigation electronics. By doing this, all of the sensitive electronics that are relied upon for navigation are protected from potential damage as the power fluctuates between extremes as the engines start.

Alternatively, if the vessel is equipped with two separate battery banks, a paralleling switch can be used to "bridge" the two banks together to maintain proper voltage during high-load situations such as an engine start. After consulting with your vessel's owner's manual to confirm that this is an approved procedure, consider paralleling the batteries before starting the engines, then disengaging this connection following a successful engine start.

A third option to consider is to have the vessel equipped with a separate battery or uninterruptible power supply (such as the Newmar Nav-Pac 12) for the exclusive use of the electronics. This alternative is becoming increasingly popular given the rise in reliance upon complex electronic circuits for navigation. This is also the safest option, as there is no effect on the electronics during power fluctuations during engine starts, and it provides redundant back-up in the event of an emergency.

Finally, the engine start system can be totally isolated from the “house” electrical system. For full redundancy the two battery banks can be charged from separate alternators, or alternatively a battery combiner or isolator can charge the two batteries from a single alternator while keeping their loads separate.

What should I do if my Navigation Computer or other accessories do not restart or do not appear to operate after an engine start?
Should this occur, power down the computer and related accessories. If necessary, hold the power button down on the computer until it shuts off. Then, power down all marine electronics, etc. via the dashboard switch. Finally, turn off the circuit breaker that controls the electronics. Wait 10 seconds for the power supplies to fully discharge, then power on the circuit breaker, the dashboard switch, and finally each piece of navigation electronics, concluding with the Maptech Navigation Computer. This will reset each device, and allow it to function normally. If problems persist after this procedure has been followed, please contact your boat technician responsible for servicing the marine electronics.


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