# Perko Battery Switch



## CJ999 (Aug 11, 2005)

I bought a perko switch and the instructions explain how to hook it up to your boat. So I made a diagram from the instructions that came with it and I am soliciting expert review before do something dumb and end up replacing a bunch of fuses, again!

Hopefully this will work.

The diagram I made:
My Webpage

The instructions that came with the switch: 
My Webpage

I used Diagram #2 from the instruction page as my guide.

Thanks,
Chris


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## Steelhead (Nov 14, 2005)

Looks OK to me. However some folks like to switch the negative side instead of the positive. Some believe it reduces spark possibilities on 12 systems. I know for wiring houses with AC current code does not allow switching the negative side. Your diagrm should work fine.

I hope









Dallas


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## CamperAndy (Aug 26, 2004)

Negitive is the prefered side to isolate the batteries.


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## CJ999 (Aug 11, 2005)

So then, should it look like this?

My Webpage


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## CamperAndy (Aug 26, 2004)

CJ999 said:


> So then, should it look like this?
> 
> My Webpage
> [snapback]82454[/snapback]​


That works.









The switch, does it have a, b , a+b and off positions???


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## CJ999 (Aug 11, 2005)

CamperAndy said:


> CJ999 said:
> 
> 
> > So then, should it look like this?
> ...


It is a four position switch, so I think the answer to your question is yes.


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## Not Yet (Dec 13, 2004)

Are you running dual 6v or dual 12v? If 6s I would wire it only to the a+b so that you are not on one battery.
WHere do you plan on mounting the switch? THere is a picture of one mounted in the front pass through. I think that would be the best but would require some drilling.

Jared


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## CJ999 (Aug 11, 2005)

12 volt system. The front pass through is a good idea.


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## CJ999 (Aug 11, 2005)

Upon thinking about mounting it inside the front pass through I decided the hole I would need to accomodate the battery cables makes this a less desireable choince than I originally thought.

Anyone have suggestions on how to mount it to the tounge frame?


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## BoaterDan (Jul 1, 2005)

CJ999 said:


> So then, should it look like this?
> 
> My Webpage
> [snapback]82454[/snapback]​


I thought on 12V systems black was typically the ground. Are the labels in the latest picture still from when you were using the positive side, or did you verify the black trailer wire was connected to the +?


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## tdvffjohn (Mar 10, 2005)

BoaterDan said:


> CJ999 said:
> 
> 
> > So then, should it look like this?
> ...


Key word, 'typically'

I have seen a lot of trailers of all makes where black is pos. A lot of people mark there wires . Always trace at least one of them to verify what it is. The ground one is usually the easiest.

John


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## CamperAndy (Aug 26, 2004)

BoaterDan said:


> I thought on 12V systems black was typically the ground. Are the labels in the latest picture still from when you were using the positive side, or did you verify the black trailer wire was connected to the +?
> 
> [snapback]82618[/snapback]​


And this is what causes a rash of reverse wired trailers in the spring with the resulting damage to the radio and sometimes the converter. The trailers are wired more like a house with White being neutral or ground and Black being hot. The 120 vac system takes the led on wire color.


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## CamperAndy (Aug 26, 2004)

CJ999 said:


> Upon thinking about mounting it inside the front pass through I decided the hole I would need to accomodate the battery cables makes this a less desireable choince than I originally thought.
> 
> Anyone have suggestions on how to mount it to the tounge frame?
> [snapback]82568[/snapback]​


Hole size would be less then an inch and you can caulk it. What mounting hard wear did it come with? I would mount it to the bottom of the tongue or the inside face of the tongue. That way you can reach it without taking the propane tank cover off.


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## Thor (Apr 7, 2004)

CamperAndy said:


> BoaterDan said:
> 
> 
> > I thought on 12V systems black was typically the ground.Â Are the labels in the latest picture still from when you were using the positive side, or did you verify the black trailer wire was connected to the +?
> ...


Be very care to double check all connection (positive & negative) a reserve of polarity can and more than likely cause damage to tyour Outback's electrical system. There are a few Outbackers that have mixed them up get the trailer ready for camping. Because of that I have labelled my connections positive and negative and do not worry about colour. My trailer does not follow the std house colour code.

Thor


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## kjp1969 (Apr 25, 2004)

CJ999 said:


> So then, should it look like this?
> 
> My Webpage
> [snapback]82454[/snapback]​


I switched the negative so that if one of my wired frayed and shorted, it would just eliminate the switch, not arc and cause a fire!
Kevin P.


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## kjdj (Sep 14, 2004)

So asuming you have 2-12 volt batteries, wiring as you show means 1 battery will be switched on at a time. Thus only one batery will supply the trailer and also be charged at a time.

I would parallel the batteries and only use one side (A) of the switch. That way all batteries are on or off.


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## Steelhead (Nov 14, 2005)

I believe the Perko switch has positions for battery "A" or battery "B" OR for batteries "A" + "B". and also all batteries off. That way you can choose to use both batteries or just "A" or "B". I believe that is the way they are designed and work.

Dallas


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## kjdj (Sep 14, 2004)

I'm just pointing out unless you are switched to A + B only one battery gets the charge. Not a good idea because by not discharging and recharging at the same rate the 2 batteries will always be unequalized. This allow the bateries to kill each other over time.

It is not designed for a travel trailer application.
Ths switch is designed for switching the load NOT the charge. Boats have a common battery charger (the alternator, tricle charger) which is hard wired to the batteries charging them both as one.

In the OB application you a switching both the charge and load.

If wired this way I would never use A+B position unless I charge in that position.

If one is not carefull one of the batteries will melt. Kids toys are a good example of what happens when you mix a chared battery with a weak one? Now try it with 2 Lead/Acid batteries.


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## CJ999 (Aug 11, 2005)

Maybe I'm not understaning every aspect of this last part of the discussion, but why couldn't I discharge them individually and charge them both at the same time?

The batteries are already unequal since one is older than the other.

And as to the earlier discussion about pos/neg black vs white, I am absolutely positive that black is positive becuase I already fried my trailer by hooking the black to the neg post and the white to the pos post! It wasn't too bad. The worst part of it was having to drive to get the proper fuses. We live in the boonies.


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## Huskytracks (Apr 18, 2005)

Looks good as to the wiring. To install on the tongue just drill and bolt on the centerline (half way from top to bottom). Or you could take a piece of metal from home depot and bolt the switch to it and then bolt the metal to the tongue beam.


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## LateralG (Feb 11, 2006)

I think I'll go with a simple high-current knife switch.


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## CamperAndy (Aug 26, 2004)

LateralG said:


> I think I'll go with a simple high-current knife switch.
> 
> 
> 
> ...


The only problem with a knife switch is that it normally makes it impossible to use the battery box top. If you don't like or use battery boxes then you are golden. If you want to keep your battery box then you need to use the remote type of switch such as the Perko.


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## LateralG (Feb 11, 2006)

CamperAndy said:


> LateralG said:
> 
> 
> > I think I'll go with a simple high-current knife switch.
> ...


Why can't a knife switch be mounted remotely?


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## CamperAndy (Aug 26, 2004)

LateralG said:


> CamperAndy said:
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> 
> > LateralG said:
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Depends on the design I guess but most of the ones you find in the RV parts places will have one end that has a battery post clamp and the other end has a bolt for a wire. Picture below is typical but not the only one you can find.


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## LateralG (Feb 11, 2006)

CamperAndy said:


> LateralG said:
> 
> 
> > CamperAndy said:
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Aha! Now I get it. Thanks, Andy.


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## BoaterDan (Jul 1, 2005)

The Perko I had on my boat had clear labels indeed, but I don't remember if it used letters or numbers.

If you really want to go all out, get an isolator as well. It isolates the two batters from each other on the charging side. So in conjunction with the switch on the discharge side you have complete control and safety in using the batteries however you want.

Seems a bit of overkill to me. I know my dual batteries will last a weekend, and I figure I'd probably have a generator if I was boonin' it for more than that.


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## BoaterDan (Jul 1, 2005)

Forgot to post this article on the isolator + switch setup.

http://www.jerrylabella.com/ship_shape2.htm


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## kjp1969 (Apr 25, 2004)

CJ999 said:


> Maybe I'm not understaning every aspect of this last part of the discussion, but why couldn't I discharge them individually and charge them both at the same time?
> 
> [snapback]82816[/snapback]​


That's what I've done for 2.5 years with good results. I leave it on A+B while plugged in, and A or B when dry camping. Then I have a reserve to switch to if/when one goes flat.
Kevin P.


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## CJ999 (Aug 11, 2005)

From what I saw in a brief shopping experience, that knife switch costs significantly more than the Perko. I paid $26 at Cableas but all the knife switches I saw cost more than $40....


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## LateralG (Feb 11, 2006)

CJ999 said:


> From what I saw in a brief shopping experience, that knife switch costs significantly more than the Perko. I paid $26 at Cableas but all the knife switches I saw cost more than $40....
> [snapback]83338[/snapback]​


Now that's worth thinking about!


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## BoaterDan (Jul 1, 2005)

kjp1969 said:


> CJ999 said:
> 
> 
> > Maybe I'm not understaning every aspect of this last part of the discussion, but why couldn't I discharge them individually and charge them both at the same time?
> ...


Without the switch in the picture - imagine a scenario where you have one vehicle battery wired to the normal vehicle system and another wired only to accessories - the issue is that the alternator senses the weak battery and pumps out the juice, thereby overcharging the more charged battery.

Now, the question is with the switch in play, when you switch to A+B does the discharge from the more charged battery to the weaker work out such that this doesn't happen.

And, for that matter, I'm just thinking that the way the charging wire from the TV is hooked to the trailer could bring this into play as well. Is that generally wired right to the vehicle battery in parallel or to the alternator?


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## LateralG (Feb 11, 2006)

BoaterDan said:


> And, for that matter, I'm just thinking that the way the charging wire from the TV is hooked to the trailer could bring this into play as well. Is that generally wired right to the vehicle battery in parallel or to the alternator?
> [snapback]83345[/snapback]​


Does someone know the answer to this?


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## CamperAndy (Aug 26, 2004)

LateralG said:


> BoaterDan said:
> 
> 
> > And, for that matter, I'm just thinking that the way the charging wire from the TV is hooked to the trailer could bring this into play as well.Â Is that generally wired right to the vehicle battery in parallel or to the alternator?
> ...


Alternator?? When towing I guess it is connected to the TV system and does receive a charge but depending on the wire size it may not be too much of one. When towing set the switch to A+B.

I would personally use the switch in the A+B position 99.9% of the time and the off position the rest of the time. I see no real advantage to two separate batteries, who wants to get up at 2 am to switch to the spare battery when the furnace will not start. That said I still will install a switch this spring. I would use the off position to do maintenance on the trailer or when I need to reset the AC/Furnace control boards.


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## W4DRR (May 17, 2005)

LateralG said:


> BoaterDan said:
> 
> 
> > And, for that matter, I'm just thinking that the way the charging wire from the TV is hooked to the trailer could bring this into play as well.Â Is that generally wired right to the vehicle battery in parallel or to the alternator?
> ...


First of all, the TV alternator and battery are pretty much inseparable. In fact they are hard-wired together, usually through some kind of fusible link. The alternator's purpose in life is to keep the vehicle battery charged. All 12V circuits connect to the battery. The 12V available at the trailer connector is hooked to the TV battery through a resettable breaker and/or fuse. When you connect your trailer, you are essentially connecting the trailer battery in parallel with the TV battery. 
If a second battery is desired in the TV (NOT trailer, now), usually a battery isolator is used. Basically, it is a big pair of diodes with a heatsink. Both the primary and secondary vehicle batteries connect to their respective terminal on the isolator. The connection between the battery and alternator is broken and attached to the common point of the two isolating diodes. This way, both batteries are charged, but they cannot power each other's load...in other words that are isolated from each other. To maintain a proper charge on the primary battery, the charge sense line from the alternater is connected directly to the primary battery to cancel out the diode's voltage drop. With respect to charging, the secondary battery pretty much goes along for the ride.
In a trailer, if more than one battery is used, an isolator won't really work because there is no alternator. Going through the isolator the charge voltage will be reduced by the diode's voltage drop (probably about 1V, at normal charging currents). So throw out that diode isolator and replace it with a switch. To charge the batteries, they can be connected in parallel. Since the charge voltage is higher than the battery voltage, current will be going into both batteries, but not necessarily equally. When not charging, it is best to separate them, and use only one at a time, because one battery will tend to discharge the other. In other words, current will come out of the stronger battery, and go into the weaker one.
As for the knife switches, Camping World has the kind that mounts on the frame, as opposed to directly to the battery terminal. The best place to put them would be on the frame where the negative battery leads (white) attach to the frame.
Hope this helps...sorry about it being long-winded.

Bob


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## kjp1969 (Apr 25, 2004)

Well okay, since we're talking about it, here's my setup: I have two 6v batteries in series, and one 12v as a "backup." (With a little angle iron and creativity, all 2 fit under the propane cover.) The single is "1" on the Perko switch, and the two-battery bank is "2." I usually charge everything for a day or two before we leave on a trip, with the switch set on "both." When we arrive, which is almost alway at a campground without hookups, I switch to the two-battery bank for the duration. If its really cold out, and the furnace runs a lot, we will usually discharge that bank in 4-5 days. Then I switch to the single battery, with the knowledge that I'd better plug in soon or we'll be totally dry.

Beyond that, I don't pay too much attention to batteries. So there you go.

Kevin P.


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## LateralG (Feb 11, 2006)

Bob,

I'm dangerous ... I've done a little reading, and have a little knowledge on the subject.

One source suggested that if two 12V batteries are electrically separated during discharge, their state of charge will be different. Then when charging, either one will be over-charged, or the other under-charged.

The risk in not separating the batteries is that there will be no warning before all power is consumed. Can the TV charging system be used at this point?

What is your configuration? How long has it been successful?


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## W4DRR (May 17, 2005)

LateralG said:


> Bob,
> 
> I'm dangerous ... I've done a little reading, and have a little knowledge on the subject.
> 
> ...


The final level of charge is a function of the charge voltage from the TV, and this is regulated. It is true that when a discharged battery is paralleled with a charged battery, the charge currents will not be equal, but as the discharged battery is brought up, the current should begin to equalize, and finally decrease to a low level when full charge is reached. One solution, if one is discharged more than the other, would be to separately charge them as well. Or at least until they are a little closer in their level of charge, then place them in parallel. Of course, this all assumes both batteries are similar in size and age, and don't have any shorted cells.
Is the source you mentioned talking about TRAILER batteries or VEHICLE batteries? If it is vehicle batteries with an isolator, it is possible to cook the secondary battery if the primary battery's voltage remains low during charging, such as it would with a shorted cell, or extremely deep discharged.
As for my setup, life is simple....single battery for now. I don't do that much dry camping. But if I were to add a battery, I would opt for a couple of knife switches. Hard to go wrong there.









Bob


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## LateralG (Feb 11, 2006)

Are there any new developements in mounting the Perko switch?

Location? How attached? Photographs?

I think this thread has adequately covered wiring hook-ups; no need to cover that again.


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