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What is the purpose of a dual battery switch?
Gmondun
#1 Print Post
Posted on 05/21/15 - 7:04 AM
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I purchased my 1985 Montauk 17 with a Perko dual battery switch and two batteries. Whenever I start my boat, I use the "all" selection on the switch to get the engine to turn over. Generally I just leave the switch set on "all" while I'm cruising around. Is there a better way I should be using the switch for charging the batteries, using the accessories, etc?

 
gchuba
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Posted on 05/21/15 - 7:22 AM
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Be careful in the "all" position. One dead battery could drain the spare. Should always go in one position or the other and NEVER switch from one battery to the other with a running boat. They have new dual battery switches that allow for both batteries to charge at the same time. With the Perko switch, the only battery charging is the one that is designated by the switch.
Garris

 
awayland
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Posted on 05/21/15 - 7:22 AM
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I do the same, start and run on both batteries. But when at anchor fishing for a long period of time switch to 1 battery to run accessories, like fish finder, radios, gps, lighting at night, saving a fully charged battery for starting. Also, to prevent fires when not using the boat, shut it completely off, to prevent something shorting out. Your bilge pump should be wired directly to the battery so it always gets power even with the switch off. Also don't change the switch with the engine running.


1970 custom 16 with 1999 Merc 2 stroke 90hp
 
gentilebrian
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Posted on 05/21/15 - 7:32 AM
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If you always use one battery then you always have a spare full battery incase you run yours down like sitting with radio on. I always used 2 big deep cycles as they are generally big enough to start most outboards. every other trip I would switch which battery I used.

 
Gmondun
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Posted on 05/21/15 - 7:42 AM
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Garris,

If I leave the switch set at "all", will both batteries charge while I'm running about?

 
tmann45
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Posted on 05/21/15 - 7:43 AM
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Most of today's battery switches are make before break and allow for switching between batteries with the engine running.

If your switch is not a make before break, you can do damage to your charging system, it would be the same as turning the switch to off with the engine running.

 
Gmondun
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Posted on 05/21/15 - 8:08 AM
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Thanks for the feedback. I've been operating on the "all" switch for several years now, but it seems that is the least optimal position unless I'm in an emergency situation to get enough power.

 
JRP
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Posted on 05/21/15 - 8:25 AM
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No, you are fine doing what you are doing. "All" is used when the engine is running for charging both batteries. If you are at anchor/drifting/electric trolling for long periods of time without running the engine, and you have a relatively high electric load, it is best to isolate the batteries by switching to one or the other. That way you are sure to have a fresh battery for starting in case the battery in use gets drawn too far down.

As mentioned, modern switches are make before break and there is no issue switching between batteries when the engine is running (unless you have a VERY OLD switch.)


19 Outrage II (1992)
 
tmann45
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Posted on 05/21/15 - 8:25 AM
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Gmondun wrote:
Garris,

If I leave the switch set at "all", will both batteries charge while I'm running about?


I'm not Garris, but YES!

 
gentilebrian
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Posted on 05/21/15 - 8:38 AM
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The switch also alerts you to issues with your charging system if you only use one battery at a time. For instance I have twins on my boat and each motor has its own batter but it goes to switches so I can choose which battery to use for which motor. Well was doing some work in the bilge and unhooked the batterys and somehow missed putting the charging cable back on the port motor. Went out a few trips and the battery slowly drained then all of a sudden the motor started to bog down. I tried to restart but no power to turn it over. switched to other battery and it started right and up and ran fine. Point of the story is if your charging system fails and your battery dies you are dead in the water if you are on all but if you can switch to the fresh battery to get you home if you only run on one at a time.

 
JRP
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Posted on 05/21/15 - 8:40 AM
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Gmondun wrote:....unless I'm in an emergency situation to get enough power.


Regarding the emergency situation... it depends.

If one of your batteries has been deeply discharged, you would NOT want to use the "ALL" switch setting. That is because the bad battery will drain power from the good battery until they are equalized. Soyou would not combine them, insyead you would keep them separate and select only the good battery to start the engine. Once they engine has been restarted, you can combine them again and they will both charge.

However, if both batteries have been equally deeply discharged, and you are trying to re-start the engine on a prayer, then yes, combining them with the "ALL" switch will give you the best chance of having enough amps to turn the starter and restart the engine.


19 Outrage II (1992)
 
Gmondun
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Posted on 05/21/15 - 10:23 AM
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JRP, thank you. I have a much better understanding of how to operate my batteries. I generally have issues with my batteries being drained and from what I gather, batteries will charge together on the "all" feature, but charge more optimally if isolated on the switch. Hoopefully I won't have to charge my batteries as much with an AC charger.

 
tmann45
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Posted on 05/21/15 - 10:34 AM
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Gmondun wrote:
JRP, thank you. I have a much better understanding of how to operate my batteries. I generally have issues with my batteries being drained and from what I gather, batteries will charge together on the "all" feature, but charge more optimally if isolated on the switch. Hoopefully I won't have to charge my batteries as much with an AC charger.


For best performance from your batteries you should always top them off after every trip unless you do not run any accessories, and unless you are running your outboard (and it has a good output) for hours, your batteries will not be fully charged.

 
DennisVollrath
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Posted on 05/21/15 - 11:13 AM
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Since you have 2 batteries, you might consider installing an Automatic Charging Relay (ACR). An example I'm currently installing on my 1985 Outrage 18 is:

https://www.bluesea.com/products/7601...24V_DC_65A

This device helps maintain safe charging of two batteries, combining when appropriate and isolating when one or more is in an over/under voltage state. It also can isolate your house battery and associated electronics during starting. A status light lets you know when it is isolated (typically due to one battery being discharged), so you get a heads up and don't combine to start. There are other more sophisticated models that prioritize charge to one of the batteries.

I'm using this in conjunction with:

https://www.bluesea.com/products/6011...ch_-_Black

which normally has the house and start batteries isolated, but with a provision for combining if need arises.

Dennis


1985 Outrage 18 with Suzuki DF140A
 
Gmondun
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Posted on 05/21/15 - 12:56 PM
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Dennis,

So that device would only come into play when I switched my batteries to "all"? I'm assuming that if I manually isolate the batteries on the switch than that device doesn't function.

 
Phil T
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Posted on 05/21/15 - 1:07 PM
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Sorry to join this thread late but since you are doing serious work on the boat's electrical system, I have to ask.....

Why do you need 2 batteries to begin with. Almost all classic and post classic Montauk owners run with one battery. Unless you have serious lighting, electronics or a trolling motor, I don't see the benefit.

I did complete electrical re-wires on both my classic Montauk and Outrage 17.



 
Gmondun
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Posted on 05/21/15 - 1:46 PM
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Phil,

The boat was set up with a two-battery system when I purchased it. I was just wondering how it can be used most efficiently.

I've seen your re-wire projects, I wish the interior of my center console looked like that.

 
DennisVollrath
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Posted on 05/21/15 - 7:17 PM
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Gmondun wrote:
Dennis,

So that device would only come into play when I switched my batteries to "all"? I'm assuming that if I manually isolate the batteries on the switch than that device doesn't function.


No, an ACR is a parallel system that is always monitoring the charging source and both batteries. You can find an installation diagram on the web page linked previously.

However, as PhilT mentions, many people run their Montauks and other boats with just a single battery unless there is a load that demand two. Mine came with two and a battery switch, and when I redid the electrical system I went to a single battery with no switch. I used a switchable breaker for the house circuits to disable loads when the boat is not being used. Simpler is often a more reliable solution.

With my Outrage, I'm adding an electric davit for prawning, as well as an electric trolling motor. Hence the 2nd battery and associated switch and ACR.

Dennis


1985 Outrage 18 with Suzuki DF140A
 
gchuba
#19 Print Post
Posted on 05/21/15 - 10:33 PM
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I am not Tmann45 but I will chime in (could not resist tmann). If you continually run and operate in the "all" position....you defeat the reasoning for two batteries in the first place. You are basically running with one big battery. The charging of both batteries from an outboards system while both are in continual use would be a trickle at best (and as stated earlier the weaker of the two batteries would steal charge from the good one) and you would be better off charging one without diverting the amps. To me the need for two batteries is like having a spare tire. One needs to be charged and in good shape for emergencies. Like Phil says, (and my opinion of the way you are using them) you may as well go for a single battery.

However, Dennis brought up a very modern and well thought out design for two batteries. I have the same system on my boat. My secondary (non starting) battery always gets the charge from the motor but the only function/draw I put on the battery is for the electronics (negligible). It is separated from the other battery. With the ACR relay.....you also protect electronics. Do study the Blue Sea system. Your wiring is already there and with some modification you would have a superior system with the charged (spare tire) available.

Garris

Dennis,

In addition to combining the charging the ACR Relay disengages the secondary battery when starting the motor. The relay is connected the the starting position of the key (not the "on" position). As you flick the start, some internal connection gets interrupted. Davits, anchor winches, wash down pumps, etc (the high amp surging starter motors).... should be on the starting battery if you are separating the electronics. All my electronics are isolated.

Editing


Edited by gchuba on 05/22/15 - 6:29 AM
 
tmann45
#20 Print Post
Posted on 05/22/15 - 7:50 AM
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gchuba wrote:
In addition to combining the charging the ACR Relay disengages the secondary battery when starting the motor. The relay is connected the the starting position of the key (not the "on" position). As you flick the start, some internal connection gets interrupted.

Garris, the Blue Sea ACR calls that Start Isolation and it removes the connection between the two batteries (opens the relay). Depending on the loads you have and your battery bank capacity, it might not be necessary on all setups. I did not need that capability and did not wire mine up to the ignition switch.

 
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