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Author Topic:   Single Engine/Dual Battery connection
Waccamaw Whaler posted 05-25-2009 02:11 PM ET (US)   Profile for Waccamaw Whaler   Send Email to Waccamaw Whaler  
The following was copied from Jim’s reference:

Single Engine/Dual Battery

“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.”

Apparently the diagram is drawn as though you are facing the rear of the boat in that the PORT battery is shown to the right. My batteries are located inside the center console. Because of the location and length of the cables I would want to have my starboard battery (right side facing forward) connected to the No. 1 position and the other battery connected to the No. 2 position. How then would the diagram look?

Do I understand correctly that, if using this setup, you can switch between batteries 1, 2 and Both while the engine is still operating?

What switch (model, mfr.) is recommend?

I’m using this with a Yamaha F90 and have two 825 CCA (WAL-Mart) batteries. One battery is brand new and the other is 8 years old. I just took the old battery to 3 different battery retailers to be tested. Each told me the battery was good. I bought the old battery with my boat and ‘think’ it was seldom ever used. Since it’s 8 years old is it trustworthy?


jimh posted 05-25-2009 02:56 PM ET (US)     Profile for jimh  Send Email to jimh     
For people familiar with electrical terms: Most OFF-1-BOTH-2 battery distribution switches are make-before-break, but, of course, check your switch.

For people unfamiliar with electrical terms:

Most battery switches made these days with the familiar OFF-1-BOTH-2 notation are designed with contacts which engage the next circuit position before they disengage the current circuit position. For a brief moment as the switch is thrown both circuits are engaged. This means that as you switch from 1 to BOTH or from BOTH to 2 there will not be an interruption in the switch output. It will always have power (from one battery or the other) at the output. Of course, check the switch you have to make sure.

If you are on 1 and switch to OFF then to 2, in other words you turn the knob in the opposite direction as in the previous example, the circuit obviously is interrupted as you pass through the OFF position.


The notation of a battery being "1" is simply conferred by how you wire it to the switch pole which is marked "1." If you want a certain battery to be "1" then you wire it to the pole of the switch which is marked "1". It is that simple.


BLUE SEAS makes a nice battery switch, but then so does BEP, PERKO, ATTWOOD and a few others.


The life of a battery is primarily determined by how it is used and how it is maintained. The number of charge-discharge cycles affects battery life, the depth of the discharges, and the method of recharging.

Would I bet the farm on an eight-year-old battery? No, but it might be in great condition. Use it and see how it works out. If you discard it you will get a core credit of $8 or more. The lead in batteries is one of the most re-cycled products we use. Batteries were "green" before this pervasive preoccupation with political proper recycling was first imagined.

jimh posted 05-25-2009 03:09 PM ET (US)     Profile for jimh  Send Email to jimh     
When choosing a switch you should select one with a current rating which is appropriate for the installation. If you have big V6 motor and need 1,100-MCA batteries, don't buy a switch rated at 100-Amperes.
Waccamaw Whaler posted 05-25-2009 11:00 PM ET (US)     Profile for Waccamaw Whaler  Send Email to Waccamaw Whaler     
Thanks for the usual great feedback
Narragansett Outrage posted 05-26-2009 10:42 AM ET (US)     Profile for Narragansett Outrage  Send Email to Narragansett Outrage     
Hmmmm. Jim, I've got the original 1983 Evinrude 235 and am about to exchange the Perko for the BEP 716 cluster (which is rated for under 125 amps). Did I mess up?
jimh posted 05-26-2009 01:58 PM ET (US)     Profile for jimh  Send Email to jimh     
The switch rating is probably for continuous current. Check its peak rating; also, check the engine starter current rating. The starter current is probably 100-ampere, or more. Many guys are using the BEP switches, however I was surprised at their compact size.
jimh posted 05-26-2009 02:03 PM ET (US)     Profile for jimh  Send Email to jimh     
Here are some specifications for a battery switch:


Make-before-break contact design allows switching between battery banks without power interruption.

Cranking Rating: 10 sec. =1,000 Amps
Intermittent Rating: 5 min. = 525 Amps
Continuous Rating =350 Amps


Those ratings are appropriate for use with most any outboard motor.

Narragansett Outrage posted 05-26-2009 08:20 PM ET (US)     Profile for Narragansett Outrage  Send Email to Narragansett Outrage     
Phew! I checked the box:

Continuous 275 amps
Intermittent: 455 amps
Cranking: 1250 Amps

Wonder why it says 125 amps on the vsr?

pglein posted 06-01-2009 02:43 PM ET (US)     Profile for pglein  Send Email to pglein     
The phyisical orientation of the batteries in relation to the switch really doesn't matter. You can have either battery be in the 1 or 2 position on the switch. It is simply important that you remember which is which. I find that labeling the batteries helps elminate any possibility for confusion.
Andrewdavis34 posted 06-03-2009 09:11 PM ET (US)     Profile for Andrewdavis34  Send Email to Andrewdavis34     
Hi all,

Here is my installation if interested. I have the Blue Sea Systems switch that Jim H is referencing and have been very happy with the service that it has provided thus far.


Waccamaw Whaler posted 06-14-2009 01:25 PM ET (US)     Profile for Waccamaw Whaler  Send Email to Waccamaw Whaler     
I installed a Bluesea 9001e battery switch according to the instructions in the reference section:

In the process of testing the switch I found that I can start the engine in all 3 positions i.e., 1 - BOTH - 2.

However, I also discovered that, without starting the engine, my GPS turns off when I turn the switch from any position to another. This being the case I'm not comfortable with the idea of switching positions with the engine running for fear of damage.

If the wiring is correct, should the GPS, (+) bus, be seeing a loss of voltage when turning the switch?


jimh posted 06-14-2009 02:18 PM ET (US)     Profile for jimh  Send Email to jimh     
According to the manufacturer, a Blue Seas 9001e has

"Make-before-break contact design allows switching between battery banks without power interruption."

jimh posted 06-14-2009 05:47 PM ET (US)     Profile for jimh  Send Email to jimh     
A device whose source of power is the Blue Seas 9001e switch should not experience an interruption in power when:

--the switch is in position 1 and is moved to position BOTH
--the switch is in position BOTH and is moved to position 2
--the switch is in postiion 2 and is moved to position BOTH

Of course, whenever the switch is moved to the OFF position the power is interrupted.

Waccamaw Whaler posted 06-14-2009 06:57 PM ET (US)     Profile for Waccamaw Whaler  Send Email to Waccamaw Whaler     
That was my understanding but it happened.

When I get the opportunity, I'm going to experiment with some other device connected do the (+) & (-) buss and see if it happens again. I'm suspicious of the selector switch but find it hard to believe with a brand new switch.
jimh posted 06-15-2009 08:48 PM ET (US)     Profile for jimh  Send Email to jimh     
Ron--I look forward to hearing the resolution of this conflict. As I see it there are two possible situations which can explain what you are reporting:

--the Blue Seas e9001 switch is defective and really does not have make-before-break contacts, contrary to all their specifications, or

--something is awry with the wiring of the switch and its related components, or the technique used to make the measurements of voltage gave misleading results, or some other circuit element failed, not the switch, causing the voltage drop out.

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