# Dual Battery hook up?



## tyler0421 (Jan 10, 2008)

I'm having a problem hooking back up my batteries. I replaced them with new ones and I thought I had hooked them up like they were but apparently not. I have two batteries and a Off-1-2-both switch. How do I go about hooking them back up?


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## lastcast (Oct 12, 2007)

http://continuouswave.com/whaler/reference/graphics/dualBatterySglEngine441x370.gif


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## tyler0421 (Jan 10, 2008)

That won't pull up for me. It says Im a thief stealing bandwith.


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## feelin' wright (Oct 7, 2007)

Should be straight forward. On you switch you have two wires the same length. These are hooked to your positive terminal on each battery. Your long wire goes forward to the ignition system.


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## tyler0421 (Jan 10, 2008)

Well Im not sure what I am doing wrong but when I had it all hooked back up I could use #1 or both but but not #2. I unhooked it the other day to just use #1 and I have nothing hooked up to #2 and a 3ft red cable and a 2ft black cable. Red to switch and then neg to neg?


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## joebuck (Oct 1, 2007)

I just did the same thing with my two batteries. I knew I would have problems if I did not label everything as I took it apart, LOL. I do have a neg to neg jumper wire in my hook up. Hope that helps.

Edit: I would try the red to the positive terminal on battery 2 and then hook up the neg to neg between the two batteries. Pretty sure that is what I've got.


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## Ocean Master (May 20, 2008)

continuousWave --> Whaler --> Reference 

*Dual Battery Wiring*


This article describes several techniques for interconnecting outboard motors and dual batteries. There are two distinct applications: single engine installations and dual engine installations. *Single Engine/Dual Battery*

The use of a single engine and dual batteries is one of the most common installations found in outboard powered boats. Interconnection is straightforward. The diagram below shows the typical wiring. 








*Dual Battery/Single Engine Typical Schematic*
NOTE: The battery positive leads are shown in red. The negative leads are shown in green for clarity; code suggests the use of yellow wire. Wiring gauge is determined by current demands and length of the run. Typically 2-AWG is used to connect to the batteries; 10-AWG is used to connect to the distribution panel. The single switch is an OFF-1-BOTH-2 switch.
_JWH._

The use of a switch and wiring like this is recommend with dual battery installations. A brief explanation of the operation of the switch in this circuit follows.
In the *OFF* position, the two batteries are disconnected from all loads. The OFF position is used when the boat is being stored or otherwise not in use. It prevents any drain from the batteries. This can be useful if a circuit has been accidently left on, say a cabin lighting circuit or similar drain. Such a load can completely discharge a battery in a day or two, leading to an unanticipated dead battery situation when you return to your boat. On some switches a key lock is provided, allowing the switch to locked in the off position. The provides another level of security in preventing the boat from being used when left in storage or unattended.
In the *1* position, all loads and charging currents are connected to the No. 1 battery (the PORT battery in the illustration). Starting current for the engine starter motor is supplied by the PORT battery. When the engine is running, surplus current developed by its charging circuit will flowing into the PORT battery. Current to lighting and other loads will flow from the PORT battery. The STDB battery is completely isolated and has no load current, nor does it receive any charging current.
In the *2* position, all loads and charging currents are connected to the No. 2 battery (the STBD battery in the illustration). Now it supplies current required by starting and running, and it receives all the charging current from the engine. The PORT battery is totally isolated.
In the *BOTH* position, the two batteries are connected in parallel. This has a number of implications. Unless the batteries have exactly the same state of charge, the combined voltage to the two batteries in parallel will sag to a voltage somewhat lower than the highest battery's terminal voltage. Current from the higher voltage battery will flow into the lower voltage battery and begin charging it. As long as the state of charge in one battery is higher than the other, the lower battery is more of a load than a source of power. Eventually, the batteries will reach an equilibrium, and they will both have the same terminal voltage. At that point they will both tend to supply current to loads that are attached to them, and they will both receive charging current furnished by the engine.
It would seem like operating in the BOTH position would be beneficial, but that is not always the case. Even thought the batteries will eventually rise or fall to the same terminal voltage when connected together, they will not necessarily become exactly the same. A battery (or any source of electrical engery) can be though of as having an internal resistance. The lower this internal resistance the greater the current it can supply. The internal resistance will also affect how the battery absorbs charging current. Even though they are connected in parallel, it is possible that they will supply unequal currents to the loads, and it is also possible that they will accept unequal currents from an the engine charging source.
If the batteries are significantly different in their age, their type of construction, and their state of charge, this unequal distribution of current can be more significant. To describe the situation in the simplest of terms, when two batteries are connected in parallel, they will probably tend to behave more like the weakest battery of the two than the strongest.
Paralleling the batteries can come in handy in some situations. For example, both batteries may be discharged to a point where neither alone can provide enough current to crank the starter motor, but combined in parallel they can turn the engine over.
If one battery is fully charged and the other is totally discharged, connecting them in parallel (by using the BOTH position) can cause very high currents to flow between the batteries. Extreme heat can be generated by the sudden charging of the discharged battery. Use caution in this situation. It is better to recondition a discharged battery by slowly re-charging it with an AC-operated battery charger.
The arrangement of the contacts of the typical OFF-1-2-BOTH permits the operation of the switch in the range of 1-2-BOTH without ever disconnecting the batteries from the load or the outboard charging circuit. This is important, as it is possible to cause damage to the charging circuit if the battery is disconnected while the engine is running. By choosing the path of rotation of the switch, it is possible to change from *1* to *2* without moving through the *OFF* position.
*Dual Engine/Dual Battery*

Dual engines and dual batteries require careful interconnection to prevent damage to the engine charging circuits. Three approaches are shown, one as believed to be used by Boston Whaler, a second alternative approach (that I have since discovered is described by West Marine in their catalogue), and a third configuration which I am currently using in my Boston Whaler.
*The Problem*

The use of dual batteries in boats is quite common, but most often the dual batteries are associated with just one engine or charging source. The wiring and interconnection of two batteries and one engine alternator is quite well covered in the boating literature. There is a less common and less written about situation that arises when there are two batteries and two engines or charging sources.
The problem with having two charging sources is that care must be taken to not connect the two chargers together in a way that damages one or both of them. Experience suggests that if two engines' chargers are wired in simple parallel and charge a common battery or bank of batteries, it is not unusual for one of the chargers to suffer a burned out stator coil. The cause of this is most easily explained if a fundamental rule of charging circuits is understood: the charger should never be operating without a load (a battery) connected.
In circuits with parallel connection of two engine charging circuits, it is likely that the voltage produced by them will not be precisely equal. If one unit has an output approximately one volt greater than the other, the effect of this will be to electrically disconnect the load from the lower voltage output engine. This may result in damage to the stator coil of the engine producing the lower voltage output.
*Boston Whaler Factory Installation*

Several models of Boston Whaler boats come rigged from the factory with dual outboards and dual engines. Below is the wiring which is believed to be currently used by Boston Whaler in these installations.








*Dual Battery/Dual Engine Schematic*
NOTE: The starboard battery positive is shown in dark red for clarity; use red wire. The negative leads are shown in green for clarity; use yellow wire. All wiring is AWG-2 unless indicated. Switchs are OFF-1-2-BOTH style.
_Adapted from a sketch supplied by Boston Whaler by JWH._

*Normal Operating Procedures*

The Whaler Factory Installation operating procedure is believed to be:

Normal operating position of PORT switch is Position *1*
Normal operating position of STBD Switch is Position *2*
To parallel batteries for starting, turn both switches to *ALL* Position. Return each switch to its normal operating position after starting.
PORT engine can be started from STBD battery by turning PORT Switch to Position *2*. Return to Position *1* after starting.
STBD engine can be started from PORT battery by turning STBD Switch to Position *1*. Return to Position *2* after starting.


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## tyler0421 (Jan 10, 2008)

I could of sworn that's how I had it hooked up. Ill re-try it when I get home. Thanks.


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## jasoncooperpcola (Jan 2, 2008)

Battery switch may have went bad. Mine quit working on number 2. Its pretty easy wiring them. Red to each battery positive, a black to the negative then a jumper hooking both batteries negative together.


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## tyler0421 (Jan 10, 2008)

well if it's bad then the one I bought at west marine is bad too because i tried changing that out as well.


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## X-Shark (Oct 3, 2007)

Look @ diagram #1.....Don't pay any attention to the Field disconnect terminals /wiring. I bet you do not have that.

http://www.perko.com/images/catalog/pdf/Fig 8501-8504 Inst (8500INS1).pdf


When you get ready for a upgrade into Y2K let me know.

That's when a BEP Cluster Switch gets installed.

It's all explained here.
http://www.pensacolafishingforum.com/f21/perko-switch-questions-85302/


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