Long run of battery cable... AWG?

[Piece715]

Re: Long run of battery cable... AWG?

I run the biggest deep cycle marine battery that I can get. I've been using WalMart batteries for the last 8 years with no problems. They're actually a Johnson Controls unit which if you do research is the same company that makes them for Interstate, Autozone, etc etc just with different brand names on them. I think it's a series 29 unit.. and with that class D amp you should be able to play for literally a few hours between charges.

Ya that is what i was thinking... as big as they get... 29 or above. Thanks for the info. If ya got any more tips or pointers just post em. I never turn down good info. I gots lots of shopping to do... just where to start:facepalm:


I haven't been yelled at due to my diagram so that is a good sign! Gonna let it sit and simmer for a couple of days with it being Easter weekend and all. I just wanna make sure its right. So comment away fellow iboaters... have a goal of two weeks before the splash!

 

[Piece715]

Re: Long run of battery cable... AWG?

Ok i just thought of something i forgot in my diagram. Fuses near the batteries. like so


Question is do i just need one coming off both of the positive posts going to the battery switch?

 

[Piece715]

Re: Long run of battery cable... AWG?

Hope everyone had a Happy Easter! The schematic is still open to scrutiny sooo comment away. I wanna try to have all the wire ordered by middle of this week.

 

[bruceb58]

Re: Long run of battery cable... AWG?

You don't want any fuses between the battery and starting the engine.

 

[Piece715]

Re: Long run of battery cable... AWG?

There aren't any... The engine starter is run to the common post of the battery switch. The Common post then feeds a postive terminal buss bar which then branches into power for the fuse block with an inline 60 amp breaker and power to the amp which also has an inline fuse (size stated in manual cant think of it off top of my head)

EDIT: well technically when thinking of it there will be when adding the fuses to the positive posts of the batteries before going to the switch. I thought all batteries required fuses pretty close to the positive post...

 

[bruceb58]

Re: Long run of battery cable... AWG?

EDIT: well technically when thinking of it there will be when adding the fuses to the positive posts of the batteries before going to the switch. I thought all batteries required fuses pretty close to the positive post...

Not the leads that are going to the starter of a motor.

 

[Piece715]

Re: Long run of battery cable... AWG?

Not the leads that are going to the starter of a motor.

If im understanding u correct then no. The leads going from the starter go straight to the common post of the switch. The leads going to the battery switch from the batteries will be fused. So those fuses going from batteries to the switch are not needed?

 

[bruceb58]

Re: Long run of battery cable... AWG?

You don't want any fuses between the battery and the switch or the common and the starter. You do want the fuse between the common and the fuse panel.

Basically, the path from the battery post through the switch to the starter should not be fused. The starter just pulls too much current.

 

[Piece715]

Re: Long run of battery cable... AWG?

Ok no fuses until after positive bus bar. So the 60 amp breaker and the fuse for the amp should be the only two listed. Thanks for the info.


My switches were wrong. Here is a revised copy with the wires in the correct places.

 

[Piece715]

Re: Long run of battery cable... AWG?

Alright guys and gals the 14 awg primary wire (red and black), heat shrink terminal connectors, and heat shrink butt connectors have been ordered! Got that accomplished last night and just got an email from Greg's marine wiring stating my order has shipped! As soon as that comes in I'll wire the switches and accessories back to the fuse block.

Now with the power wire I am still confused. I understand that the wire should be able to support the amps of the circuit. The length of the conductor should be from the source of current to the battery switch and then back to the source. In my set up it is the length of the wire from the motor to the battery swtich and from the negative terminal bus bar to the motor. Now what i need to determine is the amp drawer from my starter. I also understand that the running amp draw is much different from the amount needed during starting. I am going to check the motor's manual when I get home to see if it states the amp draw during start. From there I will be able to input all my variables into a wire gauge calculator to determine proper gauge or just refer to a chart.

What I don't understand is how to determine the gauge wire needed to run the batteries in parallel or the run of wire from the switch to the fuse block?

Now back to what I do understand or actually a clarification of what I think I understand. The fuses/breakers in any wire are used to protect the wire not the load. In my set up the 60 amp breaker is used in line from the positive bus bar to the fuse block due to the fact that the run is 10' or less with 6 awg. To explain: the 6 awg at a run of 10' or less at 3% voltage drop in a 12v system can support up to about 80 amps but you only want to run a wire at 80% capacity which is why a 60 amp breaker is being used..... Does this sound correct?

Now when shopping for terminal bus bars last night I noticed that like everything else they come in different shapes and sizes. What size (amps) bus bar would I need? To determine this do i just find a bar that will support my biggest amp load or will it need to support a summation of all amp loads run to it. I.E. the positive bus bar that has the power wire from the switch, the power for the fuse block, and the amplifier power wire attached.

If you can help with any of these areas it would be greatly appreciated. I want to learn this stuff so I can troubleshoot if needed down the road. Any threads, hints, advice, in depth explanations, websites, etc would help. Like I stated I am trying to understand the basics. I am attaching the wiring schematic to this post for further scrutiny


(if iboats opens image too small to see detail either save image and open in MS Paint or click on image after opened by iboats which puts image on own page, then click again to zoom) I will be more than happy to PM this to anyone just give me a shout. As always thanks!

 

[Piece715]

Re: Long run of battery cable... AWG?

*slight nudge*

 

[Piece715]

Re: Long run of battery cable... AWG?

Piece,

How long have I been gone? You sure got a good list of questions, fast.
Since no one has answered you yet, I'll take a stab at it. Remember there's more than one way to do everything.

Wire Gauges - They all look good for 15A curcuits (check what that radio will pull). The wire gage from the switch (battery selector switch?) to the fuse block is calcualted by the sum of the total amp draw and the distance between the switch and bus bar - neither of which I knnow - TBD.

BUS BAR SIZE? Depends on the size of your bar. Assume each screw terminal (each wire run) is good for 15 - 20 amps (use 15 A). Then add up how many screw terminals you have on the bus bar. For example: If your bus bar has 10 screw terminals (can connect 10 wire runs) then your bus bar is rated for 15 X 10 = 150 amps. If you only have 5 screw terminals then it would be a 75A buss bar. Remember 20 A may be used to rate some buss bars, but you should be drawing well less than 15A per circuit, so your good either way (except for maybe that amp). Consequently, you should be buying a bus bar(s) that'll handle the number of wire runs you have and be less concerned with amperage as long as the overall amperage divides into 15A or more for each screw terminal (for each wire run). Buy quality marine stuff (ss screws) and you'll be good.

STARTER CABLE GAUGE: General rule of thumb - use 2/0 for your application (unless you have unusually long cable runs). Your starter amperage will vary considerably depending on your battery voltage - 13V (full charge) will pull one amperage, while 11.5V (half dead) will pull considerably more amps. The CCA of your battery will come into play also, as will the outside temp and the engine (starter) temp, etc. So sizing your cables from a simple published ampre draw would be difficult to do.

That should keep you going a little longer.

Todd

This came through on my resto thread... If anybody has anything else to add please chime in? again I'm wanting to get a full understanding of this

 

[Piece715]

Re: Long run of battery cable... AWG?

(My response to Todd4 last post)

As always sir, much much appreciated. The bus bars definitely makes sense now with that explanation. After a night of staring at the boat and trying to determine set up; I have a solution to my length issue... :facepalm: (that's what she said)... cable length. I can fit one of the 6 gal gas tanks in the bow seating on the starboard side as the port side will have the amp mounted inside and that doesn't allow a tank. So i will keep the one tank in the back with both batteries and have the spare tank up front and just switch when needed. Gallon of gas weighs roughly 7+ lbs soooo 40 pounds is pretty manageable. Soo with that change I can keep the switch and bus bar in the stern.

One thing I'm not understanding is 2/0 gauge wire for the motor starter. Not exactly sure what is on the motor now but 2/0 seems very large and now at the run only being 6 feet rather than 15 prob overly excessive or am i missing something. I was think 2 awg but i feel i missing something here. 2AWG can handle 120amps at 0-15ft @ 3% voltage drop and 2/0AWG can pull 200amps at same distance. Now I know u should only load wire to 80% of its capacity; so 2/0= 160 amps and 2 AWG = 96 amps..... hmmmm THIS WOULD GO MUCH EASIER IF I WOULD JUST REMEMBER TO LOOK THROUGH MY OUTBOARD MANUAL!! sorry i just keep forgetting to look.

The switch and the bus bar on the fuse block will be the longest run on the boat other than the amp to the bus bar for the stereo; both at 6-8 feet. So here goes my run down:

Stern light= 9 watts or 0.75 amps
Bow light= 7.5 watts or 0.625 amps
Bilge= 3 amps
LED interior rope lights (for near future)= 0.84 watts per foot @ 30ft just to be safe= 25.2 watts or 2.1 amps
Clarion Head unit= 50watts x 4 or 200 watts= 17 amps
12v accessory socket= im guessing draws whatever is plugged in sooo ??
Horn = 3 amps
TOTAL: 26.475 amps without whatever is plugged into 12v accessory socket

So with looking at the a chart.. the appropriate wire gauge would be 6-8AWG... this correct?

Here is the chart I went by: http://bluesea.com/files/resources/r...ev.003-web.pdf

 

[bruceb58]

Re: Long run of battery cable... AWG?

I am hoping he meant 2 AWG and not 2/0 AWG. Even 2 AWG is more than plenty for a 50HP outboard.

By the way, I wouldn't run the outboard ground from a busbar.

Your stereo will never get close to 17A. Even if you run it fairly loud, probably will never get over 5. Size the wire for 17 but expect a lot less current.

 

[Piece715]

Re: Long run of battery cable... AWG?

I am hoping he meant 2 AWG and not 2/0 AWG. Even 2 AWG is more than plenty for a 50HP outboard.

By the way, I wouldn't run the outboard ground from a busbar.

Your stereo will never get close to 17A. Even if you run it fairly loud, probably will never get over 5. Size the wire for 17 but expect a lot less current.

That't what i was thinkin on the 2 AWG

Are you saying just have the starter ground on the neg battery post? and fuse block, stereo amp to bus bar?

The head unit actually isn't even going to supply the speakers as everything will be run from the amplifier. But I am trying to wire for my potential max just to cover my basis and avoid burning up a cable.

Thank you for ur input as always sir!

 

[Piece715]

Re: Long run of battery cable... AWG?

*tiny bit nudged*