# 2 batteries, perko switch, and breaker hookup for TM only



## Jay415 (Oct 6, 2011)

I want to have 2 batteries for my bow TM and a perko switch selector. My plans were to have the batteries as in the picture and mount the switch and breaker on the starboard transom or the rear of the seat. I was gonna wire positive from each battery to the switch and output to a 60 amp breaker then to TM. My concerns are with short/arc protection of a 4' positive run from the port battery with no breaker or fuse? How should I wire this up? Could I wire one 60amp breaker at each battery then to the switch and output to TM? How would it handle when switch was set to "all"? Would it take 120amp draw to trip the breakers? What's the best way to handle this? Do I need 3 breakers? (1 at each battery and a 3rd at the switch output to protect the TM) I really don't feel comfortable with such a long run if a wire gets accidentally nicked or something. I'd rather not set my boat on fire! :lol: Thanks! These 2 batteries will run a bow mount TM only with 6 gauge ran to the motor. I'm trying to keep wiring as simple as possible. I was also considering using 2 Minn Kota power centers ran to the selector switch, but again that would be the 2 breakers and the 120 amp question when switch was set to "all". Here is the power center. https://www.amazon.com/MinnKota-Trolling-Motor-Power-Center/dp/B001PTHKMG


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## redbug (Oct 7, 2011)

just install one breaker on the outlet side of the perko switch you will be fine


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## Jay415 (Oct 7, 2011)

redbug said:


> just install one breaker on the outlet side of the perko switch you will be fine


Ok how do I protect the port battery from a short if the wire is nicked. I'd like to have some type of protection close to the battery.


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## Bob Landry (Oct 7, 2011)

Jay415 said:


> redbug said:
> 
> 
> > just install one breaker on the outlet side of the perko switch you will be fine
> ...



Both batteries need to be fused or protected with a circuit breaker within 7" of the batteries.(ABYC Spec)


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## Jay415 (Oct 7, 2011)

Bob Landry said:


> Both batteries need to be fused or protected with a circuit breaker within 7" of the batteries.(ABYC Spec)


Didn't know it was spec, but that is exactly what I was thinking! I think I'm gonna connect the TM output of 2 Minn Kota power centers to the switch. They are protected with 60amp breakers and have the advantage of 12v sockets protected with 10amp breaker. That should simplify my wiring as I can connect my bilge to that. Plug and unplug for on and off.


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## Bob Landry (Oct 7, 2011)

Jay415 said:


> Bob Landry said:
> 
> 
> > Both batteries need to be fused or protected with a circuit breaker within 7" of the batteries.(ABYC Spec)
> ...



The bilge pump also needs to be fused according to what the amp draw is going to be. Remember the fuse/CB protection needs to be as close to the battery as ypu can get it. The purpose of the fuse is to protect the wiring, not the device.

The "spec" I mentioned is used by the big boat builders. If you are boarded and inspected by the Coast Guard or Game Warden, they aren't going to inspect ypur electrical system, but it's just good wiring practice and can prevent a fire.


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## Jay415 (Oct 7, 2011)

The sockets on the power center are protected by the 10 amp breaker but the bilge or anything else I plug into it will also be protected by the correct amperage fuse inside the plug.


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## Bob Landry (Oct 7, 2011)

Jay415 said:


> The sockets on the power center are protected by the 10 amp breaker but the bilge or anything else I plug into it will also be protected by the correct amperage fuse inside the plug.



Yes, but if the battery feeds the fuse panel, the wire from the battery to the fuse panel needs tobe protected. The fuses only protect the wire going from the fuse/power panel t the device, pump, radio, etc.


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## Jay415 (Oct 8, 2011)

I'm not arguing with you. The power center covers that. The power center has breakers on the battery box leaving the battery fully protected. It is designed for the TM to be directly connected to it. Leaving the wires that leave the battery fully protected. As for the sockets they are protected at the battery with a 10 amp breaker. If you insert a plug with a 3amp fuse in it there is no difference as to what your talking about. Fuse in a plug is an inline fuse and then a fuse panel is not needed. Wires are still protected.

The power center looks like a normal battery box but all external connections are already protected!


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## Bob Landry (Oct 8, 2011)

Jay415 said:


> I'm not arguing with you. The power center covers that. The power center has breakers on the battery box leaving the battery fully protected. It is designed for the TM to be directly connected to it. Leaving the wires that leave the battery fully protected. As for the sockets they are protected at the battery with a 10 amp breaker. If you insert a plug with a 3amp fuse in it there is no difference as to what your talking about. Fuse in a plug is an inline fuse and then a fuse panel is not needed. Wires are still protected.
> 
> The power center looks like a normal battery box but all external connections are already protected!



I agree. I wasn't familiar with thMK Power Center and I looked it up. While it does appear to be a little pricey for what you get, it will meet your described needs. I just think in terms of elaborate electrical installations, ABYC, and Coast Guard requirements on bigger boats because I deal with that so much of the time. I do wonder, given that you have the space to do it, why you would not want to do a permanent installtion with secured battery boxes and be done with it. It's easier to run an extension cord to a charger than lug two batteries back and forth.


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## Jay415 (Oct 8, 2011)

I was gonna hang an sae connector dongle (also fused) out of the battery cases so it's just plug and charge. Dongles like these. https://amzn.com/B000NCOKZQ

Now maybe you can answer this question which is my original need. The power center is designed to be hooked up directly to a TM hence the 60 amp breaker. Now with 2 batteries and the switch set to all, that is the same as 2 batteries wired in parallel. Now with 2 power centers in parallel each has their own 60 amp breaker. How would they react in a parallel wiring scheme. Would it take 120 amps of draw to trip both breakers being that it's pulling power from both batteries? Or would both 60 amp breakers trip at say 61 amps. 

I was just concern that more than 60amps would be able to flow down the line since power was being pulled from 2 batteries in parallel each with their own 60 amp breaker. It just sounds like each battery could supply 50amps down the line providing a total of 100amps and the breakers wouldn't trip. I'm just trying to understand that part of it. I hope I am explaining right.


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## Bob Landry (Oct 8, 2011)

Jay415 said:


> I was gonna hang an sae connector dongle (also fused) out of the battery cases so it's just plug and charge. Dongles like these. https://amzn.com/B000NCOKZQ
> 
> Now maybe you can answer this question which is my original need. The power center is designed to be hooked up directly to a TM hence the 60 amp breaker. Now with 2 batteries and the switch set to all, that is the same as 2 batteries wired in parallel. Now with 2 power centers in parallel each has their own 60 amp breaker. How would they react in a parallel wiring scheme. Would it take 120 amps of draw to trip both breakers being that it's pulling power from both batteries? Or would both 60 amp breakers trip at say 61 amps.
> 
> I was just concern that more than 60amps would be able to flow down the line since power was being pulled from 2 batteries in parallel each with their own 60 amp breaker. It just sounds like each battery could supply 50amps down the line providing a total of 100amps and the breakers wouldn't trip. I'm just trying to understand that part of it. I hope I am explaining right.



You're Ok with what you want to do. The breakers will trip at over 60 amps even through an A/B switch. Think of it as the battery is only drawing what it needs, it's not being force fed from the batteries.


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## Jay415 (Oct 8, 2011)

I still don't understand but I'll trust. I have been told by others also that it'll be fine. :lol:
I understand that it pulls what it needs and not force fed. Just don't understand how batteries in parallel work. Although 99% of the time the switch will be on 1 or 2 and probably never on all, except having to pass it when switching between 1 and 2 :lol: I need to just stop thinking about it and just do it. Thanks!


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## Bob Landry (Oct 8, 2011)

Jay415 said:


> I still don't understand but I'll trust. I have been told by others also that it'll be fine. :lol:
> I understand that it pulls what it needs and not force fed. Just don't understand how batteries in parallel work. Although 99% of the time the switch will be on 1 or 2 and probably never on all, except having to pass it when switching between 1 and 2 :lol: I need to just stop thinking about it and just do it. Thanks!



When you parallel two 12V batteries, the voltage remains the same. The only change is that the amp/hr capacity doubles. If the resistance of the load remains the same, the batteries will deliver the same current. With both of them selected, your TM is drawing from both batteries, but if the combined batteries see a draw of more than 60A, a C/B will open. A 60A C/B is not going to allow you to draw double the amperage. Hope this helps


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