Bigdamdork

Two Battery Switch

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Hopefully this isn't another face to palm for this forum.   I have seen 20 difference wiring schematics (including the directions from Perko) and I can't quite find the setup I have.  When I got my boat it was basically wired directly to motor and fuseblock/switches  /   negative bus. 

In the majority of the schematics I have looked at am seeing a switch panel and a positive bus par and then a negative bus bar.  My boat doesn't have switches to a positive bus and a negative bus, I just have push buttons where the fuse is built in. (I'm assuming)  I tried searching for a picture for 20 minutes and and cannot find one that looks like my panel I dropped a picture in below showing the backside of the positive switch panel and the negative bus sitting next to it.  

So my conundrum is when I go to Battery 1 everything works great.....also in both position and battery 2.  Low pressure alarm sounds on motor and when I turn on cabin lights they all come on no matter what the switch position.   My understanding of this switch is no power to accessories when power to motor and vice versa.  I swapped the #1 and #2 cables around and same thing.  This part I'm sure is irrelevant other than when the dust settles I want to know which is my house and which is my starting battery.  Long story short is everything is hot all the time on any position.  Conversely everything also shut off when switch is set to OFF.  I still disconnected all the battery cables before hopping off the boat this weekend just in case. 

Any thoughts?   Thanks again for any advice.  

(oh...yes...I know the 10g wire going to my negative bus is red....it's all I had on the boat.  It goes to a negative terminal per my sketch) 367632519_BatterySetup.thumb.png.1b119b887d364d8a4cc50f63b9eac813.png

IMG_1872.JPG

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Your diagram looks like the "standard" switch configuration.  I can't quite make out your text.  

Is there a short to ground somewhere?  Poor or corroded ground connections can sometimes feed +12VDC backwards to unintended devices to their chassis ground.  I had an old GMC Suburban that was haunted that way - activating the glow plugs would cause the windshield wipers to come on, and the smoke kept leaking out of any radio I put in it. :huh: 

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9 minutes ago, toddster said:

Your diagram looks like the "standard" switch configuration.  I can't quite make out your text.  

Is there a short to ground somewhere?  Poor or corroded ground connections can sometimes feed +12VDC backwards to unintended devices to their chassis ground.  I had an old GMC Suburban that was haunted that way - activating the glow plugs would cause the windshield wipers to come on, and the smoke kept leaking out of any radio I put in it. :huh: 

All the battery cables are brand new tin coated copper 1/0 gauge.    

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If I'm reading correctly I think you're expecting the battery switch, in some position, to provide power to only start the engine and not provide power to accessories. If that's the case I think you're assuming the switch does something it doesn't do. The switch only connects the selected battery ( or batteries) to both your breaker panel and to the engine. It's up to you to know which is the house battery and which is the starting battery and use the switch accordingly.

Apologies if I've misinterpreted your text.

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It sounds like your battery switch is wired the normal way.  House and engine loads are all on the output of a single battery switch.  The battery switch can switch between house and starting batteries, or join them.

The other methods that allow you to disconnect house or engine distinctly, or control which battery is used for each of those loads independently require at least two battery switches.

 

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53 minutes ago, Alex W said:

It sounds like your battery switch is wired the normal way.  House and engine loads are all on the output of a single battery switch.  The battery switch can switch between house and starting batteries, or join them.

The other methods that allow you to disconnect house or engine distinctly, or control which battery is used for each of those loads independently require at least two battery switches.

 

Yeah....so I might be misinterpreting what the switch does entirely.   Does the switch just determine which battery power is being pulled from?  That makes a ton of sense if this is the case.   Everything is hot when you turn it on but you are only pulling from Battery 1 or Battery 2 or Both according to the switch.    For some reason in my head I thought it switched back and forth.  So when you are using the staring battery the lights wouldn't work and vice versa.  It sounds like all the switch does is determine which battery is powering the whole system.  Is this accurate? 

I'm going to feel so much better if it is. :

 

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18 minutes ago, yllek said:

Yes.

Go ahead, feel better.

Thanks!  

 

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You are correct regarding the function of the switch - it's only a selector that connects either or both batteries to the "common" output.

If you want to have a "proper" start battery, move the wire that leads to the starter directly to the start battery positive terminal.

However, it's probably the case that your engine's alternator output is connected to the cable you show as being connected to the starter. It should be labeled start/alternator in your drawing and you cannot move that cable to the start battery positive as then you'll never charge your other battery.

As drawn, your entire system really only does something useful when the battery switch is in the "both" position as if you run on either battery independently you'll only charge that battery and then the two will have different states of charge and switching between them will cause massive current to flow from one to the other. This can work ok with lead-acid batteries, but it can be dangerous with any kind of battery technology.

If you want separate batteries, you need to figure out how to charge and discharge them separately. Combining them defeats that entirely.

 

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3 hours ago, Moonduster said:

You are correct regarding the function of the switch - it's only a selector that connects either or both batteries to the "common" output.

If you want to have a "proper" start battery, move the wire that leads to the starter directly to the start battery positive terminal.

However, it's probably the case that your engine's alternator output is connected to the cable you show as being connected to the starter. It should be labeled start/alternator in your drawing and you cannot move that cable to the start battery positive as then you'll never charge your other battery.

As drawn, your entire system really only does something useful when the battery switch is in the "both" position as if you run on either battery independently you'll only charge that battery and then the two will have different states of charge and switching between them will cause massive current to flow from one to the other. This can work ok with lead-acid batteries, but it can be dangerous with any kind of battery technology.

If you want separate batteries, you need to figure out how to charge and discharge them separately. Combining them defeats that entirely.

 

You are correct, Starter/Alternator cable.  One single cable going to engine then up to common on the switch.   I have read up that I should start with Battery One (cold cranking amp) and then switch to "all" to charge both batteries.  If the motor is running I probably won't leave it on one or the other.  I just wanted to make sure if we are sitting on the boat one night we leave it on house battery until I know what that translates into in amp hours.   I have a battery monitors (cheap LED one) and I'll be watching those like a hawk and will probably upgrade everything to a better monitoring system in the future.  For the next year it's really going to be something we sail in the day and maybe spend the night on during the weekend.  No multi day trips planned in the immediate future. 

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You have the standard two batt setup. Which ever batt is selected by the switch powers everything. Charge output from alt also goes only to selected batt. Normal usage for this setup is to alternate back & forth between the two batts to keep lifespan equal. So one trip batt 1 is house & B 2 is eng. Next trip reverse usage. Starting an engine which is in good condition (starts quickly) doesn't take much power. So start on one eng, then switch to 'both' while motoring to charge up both batts. Stop eng, switch to 'house' batt while sailing/anchored. This keeps one batt fully charged ready to start engine.

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It's the dumbest battery system known to man. You're lugging around an extra battery (50% of capacity and weight) and choosing to never use it. And, when you do run down one battery and try to switch to the other, you first have to join the two together, which encourages very, very, very high current to flow from the charged battery to the discharged battery.

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You can rotate the switch thru the 'OFF' position when you know one batt is flat. Or just switch really fast & minimize the amount of current flow.

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Amplifying what The Toddster said: inspect ground connections and replace anything suspect, starting with failed/failing connections like this one.

It's a little thing, but it makes all the difference in the big picture. You'll save yourself a lot of time and aggravation in learning and managing your boat's electrical system if you can first ensure that the constituent components are actually doing what they're supposed to be doing. I learned that the hard way.

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Edited by StoMo
Left out important context.

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Recommend you remove this switch and buy three separate switches one to isolate +Ve from each battery and the 3rd switch for an emergency parallel switch to allow the house battery to assist with starting the engine in case the starter battery looses its charge. You will also need a voltage sensitive relay to provide charge to the house battery when the engine is running and voltage output is greater than 13.5 (typically), this Arrangement is not applicable to lithium ion batteries when a dc dc charger will be required instead of the VSR to limit current.

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17 hours ago, Chucky said:

Recommend you remove this switch and buy three separate switches one to isolate +Ve from each battery and the 3rd switch for an emergency parallel switch to allow the house battery to assist with starting the engine in case the starter battery looses its charge. You will also need a voltage sensitive relay to provide charge to the house battery when the engine is running and voltage output is greater than 13.5 (typically), this Arrangement is not applicable to lithium ion batteries when a dc dc charger will be required instead of the VSR to limit current.

you can actually do this with 2 switches, where the 'both' settings become the emergency parallels. I have this on one of my boats. works great. we use an echo charge to keep the start and house banks balanced.

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