Battery and Power wire gauge

[trayson]

My current setup is as follows:

• Two marine deep cycle batteries (typical walmart/costco lead acid batteries)
• Perko switch
• Kicker 700.5 amp (class A/B for cabins, Class D for sub)
• Precision Power P600.2 (class D amp)

So when I took a look at my setup, I found that whoever did my stereo system wired the two amps with 4 gauge to a distribution block, then wired 4 gauge directly to one of my batteries. Both batteries are wired to the Perko switch with 4 gauge.

I think it's a poor design to have the amplifiers wired to bypass the switch, so I intend on re-wiring the lead from the distribution block to go to the perko switch. The run looks like it will end up being about 6 to 7 feet. Maybe 9 or 10 feet if I relocate the distribution block closer to the power terminals of the amps and in turn shortened the run from the distribution block to each of the amps.

What gauge wire should I run from:

1. The batteries to the perko switch?
2. From the Perko Switch to my amplifier distribution block?
3. From the Distribution block to each of the amps?

[mmandley]

I personally do not attach my Amps to the Perko switch. Only Batteries, and Alt.

From your batteries to the Perko 2 gauge
From the batteries to the Distro 2 gauge for 2 amps, if you goto larger amps, or more then 0 guage

I like to use the analogy of water pipes, if you have 2 houses that have a 4 inch pipes, then you want to use a pipe 2xs as big, which in Wires is 2 gauge.

I personally run my power and ground stereo distro to my + - battery terminals. Then I run the battery + to my perko for each bank respective to the Perko 1/2 sides.

If you wire the stereo to the common side of the Perko then the stereo will always be draining a battery and you won't be able to isolate it.

[jstenger]

Unfortunately, 2 gauge does not carry twice the ampacity of 4 guage.

If we stick to the middle of the ampacity chart and use the values for 75 degree C wire @ an air temp of 86 degrees F, then the ampacities are:

4 gauge = 125 amps
2 gauge = 170 amps
0 gauge (1/0) = 230 amps
00 gauge (2/0) = 265 amps

If you use 90 degree wire, the ampacity values are higher.

I would run 1/0 directly from the battery to the distribution block and 4 gauge from the distribution block to the amps. 1/0 to 4 gauge distribtion blocks are easy to find on Ebay.

[MLA]

If you wire the stereo to the common side of the Perko then the stereo will always be draining a battery and you won't be able to isolate it

This is incorrect and actually describes your setup to a T. Your stereo will always be drawing from one battery and you have no control over it. With the audio load wired to the common, the load will only draw from the battery in which the switch is turned to.

For the sake of clarity, lets assume the audio is wired direct to #2 battery. You can swap the #1 and #2 in my examples if one likes, as the scenario would be the same

*When wired battery direct, the battery cannot be isolated from the loads

*When the switch is turned #1, boat draws from #1, audio still draws from #2 but alternator only charges #1, audio battery goes dead

*When switch is on #2 boat and audio draw from #2 and alternator charges #2

*When turned to BOTH or 1/2, depending on your switch nomenclature, audio and boat draw from BOTH batteries and alternator charges boat while engine is running

* When switch is OFF, audio still draws from #2.

The dual battery switch is nothing more than a manual isolator. If you wire loads battery direct, you bypass the switch, reducing the function of the switch. With all loads on the common, OFF isolates the batteries from all loads. When set to 1 or 2, the other battery will be isolated from all loads.

Not trying to pick on you Mike. Your system is not wrong, just not ideal IMO, but your statement was not accurate regarding wiring loads to the common of the switch.

Tryson,

I would suggest 1/0 for the battery+ cables and the B- linking the battery grounds. I would also suggest using 1/0 for the amps B+ and B- trunk lines. Way overkill for the current setup given the distance, but plenty of room for future growth. 4ga would likely be borderline minimum, 2ga would be most accurate if you crunched the numbers, but since you are already needing 1/0 for the battery cables. Not a huge difference in cost to just purchase 1/0 for amp trunk line and battery cables.

4ga branch lines from the distribution blocks to the amps.

[slipperyrockTKE300]

speaking of distribution blocks - can you guys suggest one that has a minimum of 1/4" terminal studs and possibly a cover?

I need to cut down on the number of cables connected to the perko..

Trayson - would it be possible to put up a picture of the one you use?

[trayson]

speaking of distribution blocks - can you guys suggest one that has a minimum of 1/4" terminal studs and possibly a cover?

I need to cut down on the number of cables connected to the perko..

Trayson - would it be possible to put up a picture of the one you use?

This is the one that was on my boat. I don't know if "block" is technically the right term, but it's what goes from one cable to the two for the amps. Looks like a fuse in there too? I pulled back the rubber hoods that go over the posts.

[mmandley]

This is incorrect and actually describes your setup to a T. Your stereo will always be drawing from one battery and you have no control over it. With the audio load wired to the common, the load will only draw from the battery in which the switch is turned to.

For the sake of clarity, lets assume the audio is wired direct to #2 battery. You can swap the #1 and #2 in my examples if one likes, as the scenario would be the same

*When wired battery direct, the battery cannot be isolated from the loads

*When the switch is turned #1, boat draws from #1, audio still draws from #2 but alternator only charges #1, audio battery goes dead

*When switch is on #2 boat and audio draw from #2 and alternator charges #2

*When turned to BOTH or 1/2, depending on your switch nomenclature, audio and boat draw from BOTH batteries and alternator charges boat while engine is running

* When switch is OFF, audio still draws from #2.

The dual battery switch is nothing more than a manual isolator. If you wire loads battery direct, you bypass the switch, reducing the function of the switch. With all loads on the common, OFF isolates the batteries from all loads. When set to 1 or 2, the other battery will be isolated from all loads.

Not trying to pick on you Mike. Your system is not wrong, just not ideal IMO, but your statement was not accurate regarding wiring loads to the common of the switch.

Tryson,

I would suggest 1/0 for the battery+ cables and the B- linking the battery grounds. I would also suggest using 1/0 for the amps B+ and B- trunk lines. Way overkill for the current setup given the distance, but plenty of room for future growth. 4ga would likely be borderline minimum, 2ga would be most accurate if you crunched the numbers, but since you are already needing 1/0 for the battery cables. Not a huge difference in cost to just purchase 1/0 for amp trunk line and battery cables.

4ga branch lines from the distribution blocks to the amps.

No I get your point, and you are right. I do mine differently but the way you are describing does allow 100% isolation when in the OFF position. That is the idea goal.

I wire mine more so its completely isolates my stereo from the starter battery. This way I never have a chance at a dead starter battery.

[MLA]

This way I never have a chance at a dead starter battery.

This is just not the case. You still have a chance at running the main cranking battery down, just as theres a chance with the other configuration.

In order for your stereo bank to receive any charge from the alternator when the engine is running, you would have to run with the switch in BOTH or what ever bank your amps are wired to. If running on BOTH and if you drop anchor and forget to switch from BOTH, the stereo is still drawing from both banks.

A system with the least amount of chance for the stereo to run down the cranking, would be a dual circuit plus switch an ACR. Beyond that, you would have to have a stand-alone bank.

[slipperyrockTKE300]

My stereo is wired isolated from the starter battery...My starter battery died on me while on the lake this past Friday. Started the boat from the stereo battery.

Thank god for two batteries!!

[mmandley]

This is just not the case. You still have a chance at running the main cranking battery down, just as theres a chance with the other configuration.

In order for your stereo bank to receive any charge from the alternator when the engine is running, you would have to run with the switch in BOTH or what ever bank your amps are wired to. If running on BOTH and if you drop anchor and forget to switch from BOTH, the stereo is still drawing from both banks.

A system with the least amount of chance for the stereo to run down the cranking, would be a dual circuit plus switch an ACR. Beyond that, you would have to have a stand-alone bank.

No this is not the case. I said I use an ACR and trust me, I've killed my stereo bank several times before I went with 6v golf cart batteries and every time my body cranks right up.

My stereo is weird to my batteries direct, even when I ran a Perko so the starter was always isolated from stereo.

My stereo has no connections to my house battery unless I combine everything. I only combine after my boat is running to show the stereo to play while charging.