How thick should the batterij power kabel be ?

[talitje]

may sound like a silly question ,See this is the situation ,My boat(self build Mahogony wooden 2 seater (with 3 layers of fiber glas because of big engine)Replica F1 from the 60's , boat is almost finished with lots of help from i boats by reading lots of forums even the engine i choose because of the forums)the boat is 4 meters(13ft) and usualy the battery is nearby the engine ,but because of boat shape (space) and size and some extra engine (h.p) kilo's then the boat was suposed to carry(35 kg more)i definitly want the battery in front where there is space ,Wat i want to know is how Thick should the battery cable's be if i make them 4,5 meter instead of the 1/2 meter they are now, on a 100 ah battery on 150 h.p 6 inline(instead of 85 hp) i dont want hot or melted cable's when starting up the engine my options in thicknes is 16mm is 0,63 inch ,25mm is 1 inch,35mm is 1,38 inch ,or 50mm is 2 inch ,i dont want melted or hot cable's greetings

 

[crab bait]

Re: How thick should the batterij power kabel be ?

as big/thick as you can..<br /><br /> your standards(holland) an the usa are soooo different..<br /><br /> i'd say at 4/0 (ought) american wire gauge ( awg) at minimum.. <br /><br />i'd even go bigger,, to 2/0 if'n cost ain't too great..

 

[talitje]

Re: How thick should the batterij power kabel be ?

okay thanks fore the fast reply crab bait !

 

[FreeBeeTony]

Re: How thick should the batterij power kabel be ?

160hp IL6 in a 13ft boat?<br /><br />Sounds juas a bit overpowered.

 

[jlinder]

Re: How thick should the batterij power kabel be ?

Anyone know what the starter motor on this engine draws? If we have that we can calculate the minimum wire size.<br /><br />crab bait - you have it backwards - 4/0 is bigger than 2/0. 2/0 is about .25 ohms/ft. and 4/0 is about .16 ohms/ft.<br /><br />You might want to look at welding cable. Very flexible, easy to find (at welding supply places). <br /><br />I am just not sure about corrosion. Whatever you use make sure to use a good crimp connector on the end then seal it with adhesive lined heat shrink to make it water tight.<br /><br />You could ask the electrical supplier if they can put the crimp connectors on for you.

 

[18rabbit]

Re: How thick should the batterij power kabel be ?

Jack - there is tin plated welding cable made, tho it isn't nearly as common.

 

[jlinder]

Re: How thick should the batterij power kabel be ?

18R - I didn't know that. Thanks.

 

[talitje]

Re: How thick should the batterij power kabel be ?

Thanks a lot boys fore the reply's ,Babylon boater , its a bit overpowered yes max rated 85 h.p ,but i couldn't find a desent 85 h.p(would you like a picture of the beast?give me a e mail adres)Jack L & 18 R,look i can get koper core batterij cable's + Red or - black in any lengt and thicknes i want ,but its either 0.63 inch /0.98 inch/1.38 inch /1.97 inch an so on an so on til 3.50 inch ,i dont want to put on to to thick wires ,want to be just on the safe side ,i dont have a wire gauge so lets talk inches what size should i juse ?<br />forget the size of engine and boat i know its absurd

 

[Paul Moir]

Re: How thick should the batterij power kabel be ?

4/0 (Pronounced Four Ought) = 11.7mm diameter = 0.46 inch<br />2/0 = 9.27mm diameter = 0.36 inch<br /><br />This is the diameter of the copper part, not the insulation. I like the welding cable too: it's very flexible. 4/0 seems way overkill to me for a little I-6 outboard motor's starter, but bigger is always better. Personally I think #1 would be fine (7.35mm) for that distance and load. We are talking about an outboard here right? What brand?<br /><br />JackL, you've got ohms/Km (1000 meters) there not ohms/ft. You folks figure we can stick with metric here to avoid confusion?

 

[jlinder]

Re: How thick should the batterij power kabel be ?

Take a look at this site http://www.powerstream.com/Wire_Size.htm for wire guages<br /><br />Paul - right you are about resistance. The site above has both and I just read the wrong column.<br /><br />With a total of 9 meters (4.5 each way) I would not be worried about the cable current capacity but the voltage drop. As long as you are doing it the heavier cable will deliver more of the battery voltage to the starting motor.<br /><br />Quick top of the head calculations shows about 2.5 volt drop in 10 meters if the starting motor draws 100 amps.

 

[Paul Moir]

Re: How thick should the batterij power kabel be ?

That's a handy site Jack L. Down at the bottom is a nice little calculator. It does the 4.5m - 9m calculation automatically (Enter 1 way distance). But I get with 100A:<br /><br />4/0 (12mm) 0.2v<br />2/0 (9mm) 0.3v <br />#1 (7mm) 0.4v<br /><br />But those decimal points are starting to dance around a bit on me. One too many scotch I think. Happy new year!

 

[jlinder]

Re: How thick should the batterij power kabel be ?

I did not even look down to the bottom to find the calculator. Also shows what happens when you try to do math in your head.<br /><br />Looks like the 2/0 cable would be fine, based on our assumption of 100 amp draw.

 

[talitje]

Re: How thick should the batterij power kabel be ?

i'm almost al satisfied , thank you all ,jack L ,Paul Moir and you all its a Mercury 150 h.p inline 6 the (batterij cable lengt) distance between batterij and outboard is going to be 15 ft ,thinking of using a 105 ah batterij my options are 120 ah thinking that that should be overkil (my rectifier works wel)but back to the cable so the advise is copper core diameter should be around 0,46 inch . Happy boating in the new year !!

 

[Moody Blue]

Re: How thick should the batterij power kabel be ?

Great reference site Jackl. I am somewhat confused about the gauge sizes though. I have always thought that a 2ga is heavier than a 4ga as shown in the reference chart. You guys are saying that the 4/0 is heavier than the 2/0. Where do the x/0 ratings come in?

 

[18rabbit]

Re: How thick should the batterij power kabel be ?

Rod - you are correct...for wire, the smaller the number, the bigger the conductor. But once you get to size 0 (zero) there is nowhere else to go for bigger wires, so you keep adding zeros for them, i.e. 0 is smaller than 00,which is smaller than 000. So a 4/0 (that means 0000) is bigger than 2/0 (00) wire.<br /><br />I hope that made sense.<br /><br />Edit: Just reread your question. A 2ga wire is bigger than a 4ga wire, but both are a lot smaller than a 00 (2/0ga) or a 0000 (4/0ga). <br /><br />Here, smaller to bigger:<br /><br />16ga<br />14ga<br />12ga<br />10ga<br />8ga<br />6ba<br />4ga<br />2ga<br />0ga (a.k.a. 1/0)<br />00ga (a.k.a. 2/0)<br />000ga (a.k.a. 3/0)<br />0000ga (a.k.a. 4/0)

 

[jlinder]

Re: How thick should the batterij power kabel be ?

Not really sure where the 2/0, 3/0, 4/0 came from. Guess they needed to do something once they got to zero and needed more.<br /><br />Here's a handy reference you can keep in your head. Every time you go up or down by 4 guages you double or half the current carrying capacity. <br /><br />For example it 14 ga. can carry 15 amps, 10 ga. can carry 30 amps and 18 ga. carries 7.5 amps. <br /><br />Now remember that 14 ga. carries 15 amps, and 12 ga. carries 20 amps (wiring code for the US) and you can figure out safe current capacity for any wire.<br /><br />Note that this is safe current carrying capacity. The other factor you need to consider is voltage drop, which is critical in 12 volt systems. There is always some voltage lost in the wires, and this becomes a problem as the current increases and the wire runs get longer.

 

[18rabbit]

Re: How thick should the batterij power kabel be ?

A real long time ago read something about “wire gauge" referring to the number of times a piece of size 0 copper wire is pulled thru dies to reduce its diameter. The smaller the wire, the more dies it needs to be pulled thru, i.e a 16 gauge wire is pulled thru 16 dies to get it to the size it needs to be. A 14 gauge wire is only pulled thru 14 dies, hence it's smaller gauge number, but larger diameter.<br /><br />That’s my memory of “wire gauge”, maybe right, maybe wrong, but doesn’t explain the 00 thru 000000 gauge wires.

 

[Moody Blue]

Re: How thick should the batterij power kabel be ?

Now that I understand the gauge nomenclature, I see that the 4/0 gauge recommended for talitje's application is HUGE. I am running 10ft long cables in 4ga for a 40hp motor and have never had a problem. Am I just lucky? If I recall correctly the rated current capacity for a 4ga cable is something like 100amp. What kind of current would a starter on a 150HP motor draw?

 

[Paul Moir]

Re: How thick should the batterij power kabel be ?

I really have no idea. But somewhere in the back of my head I remember BRP saying... Oh wait, I remember it was in a post I bookmarked:<br /> http://continuouswave.com/ubb/Forum6/HTML/000565.html <br /><br />Now that's for a V-4 though, but it gives you an idea. I've cranked my 33hp over with doubled up #18 zipcord once, but it didn't crank too fast and the 'cables' got distressingly warm. The old 60's 40hp engines got shipped out with #4 or #6 depending on what year. But don't forget with starter motors as the voltage goes down, the current goes up. So bigger is better.

 

[jlinder]

Re: How thick should the batterij power kabel be ?

RodC,<br /><br />I guess you are right, 4/0 is overkill. Probably so is 2/0. <br /><br />Based on a pure guess of 100 amps, 4 ga. would be too light. 2 ga. would probably be fine, but when you consider the extra cost of 0 ga. against the amount of work you have invested in the project I would consider it.