What guage wire? Battery to Fuse Panel

Anything electric, AC or DC

What guage wire? Battery to Fuse Panel

Postby fornesto » Thu Jun 28, 2007 6:16 pm

What Guage should I use to connect the Battery to the Fuse Panel? Figure I've got a max draw of 60 amps. They're about 6' apart. How about for the ground?
User avatar
fornesto
Donating Member
 
Posts: 765
Joined: Fri Jun 25, 2004 5:12 pm
Location: Carmel Valley, California

Postby Ken A Hood » Thu Jun 28, 2007 6:33 pm

http://bart.ccis.com/home/mnemeth/12volt/12volta.htm

http://www.rbeelectronics.com/wtable.htm


So going by the tables listed in the links;

60A @ 6' =8 Gauge (Minimum) from the 1st link ***
This table leans a bit towards heavier wire than is absolutely necessary, but that's actually safer in the long run. Always provide fuse protection of any new wiring that you install. The fuse should be sized so as to protect the wiring from meltdown.***

100A @ 7' = 10 Guage (from the 2nd link).....seems you can almost double the amperage and go with a lighter guage wire??

I'd go with the 1st link; since it's an article written for RV'ers
Disclaimer: I in no way resemble the avatar shown. Furthermore, I in no way have any affiliation to the Trailer Park Boys and more specifically Bubbles!
User avatar
Ken A Hood
500 Club
 
Posts: 841
Images: 42
Joined: Sun Apr 18, 2004 8:15 pm
Location: ON CANADA

Postby Tear Les » Thu Jun 28, 2007 9:20 pm

I'd suggest 8-gauge wire; at 60-amps you're at the maximum amperage (at any length) for 10-gauge wire and that's in free air and not bundled. I don't think you'll find too much cost difference for your run.

Put a fuse or circuit breaker as close the to battery as practical to protect the wiring run to the main panel.

The ground wire is the same size.

:thumbsup:
Les Lampman
Tear Les
Teardrop Master
 
Posts: 244
Images: 13
Joined: Thu May 17, 2007 9:52 am
Location: Whidbey Island, WA
Top

Postby jdarkoregon » Thu Jun 28, 2007 10:58 pm

Tear Les wrote:Put a fuse or circuit breaker as close the to battery as practical to protect the wiring run to the main panel.


Les, that is a great suggestion. I will change the placement on my fuse, thanks

John
Innovation is essential
The world can be better
ImageImage
User avatar
jdarkoregon
Donating Member
 
Posts: 1235
Images: 47
Joined: Mon Aug 22, 2005 7:07 pm
Location: Oregon, Sublimity
Top

Postby Tear Les » Fri Jun 29, 2007 10:33 pm

jdarkoregon wrote:
Tear Les wrote:Put a fuse or circuit breaker as close the to battery as practical to protect the wiring run to the main panel.


Les, that is a great suggestion. I will change the placement on my fuse, thanks

John


Thanks John. :) If something goes wrong in the main box you don't want the main feed wire to carry so much current that it melts its insulation and starts a fire.

I said to put a fuse or circuit breaker in there to protect the wire but in reality you're putting it in there to prevent a fire; that's actually the reason that circuit breakers and main fuses exist (even in houses).
Les Lampman
Tear Les
Teardrop Master
 
Posts: 244
Images: 13
Joined: Thu May 17, 2007 9:52 am
Location: Whidbey Island, WA
Top

Postby Gerdo » Sat Jun 30, 2007 9:55 am

60 Amps?

WOW What are you running? I ran 10 awg with a 30 amp fuse at the battery. Even it I turned everything on it wouldn't add up to 30 amps. Even if it did I took the same approch that houses do. An average house has a 150-200 amp main but if you add up all the amps available on all of the single breakers it would add up to some times twice that. (I am acounting that a 150 amp main is one leg, houses have two legs, 150x2=300) Rember also that you may have a few lights on one 15 amp circuit but they may only draw 10 amps max.

Figure out your usual load, add some and that is your max safe load. Size your wire to that. Protect the wire with a fuse at the battery sized to the wires safe load.
User avatar
Gerdo
1000 Club
1000 Club
 
Posts: 1356
Images: 156
Joined: Mon Apr 25, 2005 12:02 am
Location: Littleton, Colorado
Top

Postby bdosborn » Sat Jun 30, 2007 11:39 am

Tear Les wrote:I'd suggest 8-gauge wire; at 60-amps you're at the maximum amperage (at any length) for 10-gauge wire and that's in free air and not bundled.


A #8 is pretty small for 60 amps and a #10 is way too small. The size of wire is dependent on the type of insulation as well as how it is installed. Wires in conduit run hotter than wires in free air. Here's a chart that gives ampacity based on THHN insulation and wire installed in conduit. THHN insulated wires can be found at the home center.

Image

Bruce
2009 6.5'X11' TTT - Boxcar
Image
Boxcar Build
User avatar
bdosborn
Donating Member
 
Posts: 4175
Images: 450
Joined: Wed May 05, 2004 11:10 pm
Location: CO, Littleton
Top

Postby Mike C. » Sat Jun 30, 2007 2:17 pm

fornesto,

I have sold AC electrical for over 30 years and I would not go less than a #6 gauge, and then I would use welding cable, which is what we sell to manufacturing plants to hook up their battery chargers. If you can't find at Home Depot or Lowe's, go by your local wholesale electrical distributor and most will sell to you for cash.

But the most important question I have is how do you get 60 Amps continuous out of a single battery. What are your loads? And how long do you expect it to run? Are you basing this on your battery, or on the size of your fuse panel?
Uncle M ( Mike )
User avatar
Mike C.
our Uncle M
 
Posts: 4140
Joined: Mon Jun 18, 2007 10:13 pm
Location: Southwest, MO
Top

Postby Miriam C. » Sat Jun 30, 2007 2:42 pm

This might be helpful to folks like me who might not understand or remember the techy stuff.

The most important consideration in buying a deep cycle battery is the Reserve Capacity (RC) or Ampere Hour (AH) rating. RC is the number of minutes a fully charged battery at 80 degrees F is discharged at 25 amps before the voltage falls below 10.5 volts. Some deep cycle batteries are rated in Ampere Hours. To convert Reserve Capacity to Ampere Hours, multiple RC by .6. For example, a battery with 120 minute RC will have approximately 72 Ampere Hours. This means that the battery should produce one amp for 72 hours of continuos use. More RC is better in every case. To increase RC, connect two six volt batteries in series or more 12 volt batteries of the same type in parallel. To increase the voltage connect two or more in series.


http://www.repairfaq.org/ELE/F_deep_cyc ... PCYCLE_008
“Forgiveness means giving up all hope for a better past.â€
User avatar
Miriam C.
our Aunti M
 
Posts: 19673
Images: 149
Joined: Wed Feb 15, 2006 3:14 pm
Location: Southwest MO
Top

Postby Tear Les » Sat Jun 30, 2007 9:00 pm

bdosborn wrote:
Tear Les wrote:I'd suggest 8-gauge wire; at 60-amps you're at the maximum amperage (at any length) for 10-gauge wire and that's in free air and not bundled.


A #8 is pretty small for 60 amps and a #10 is way too small. The size of wire is dependent on the type of insulation as well as how it is installed. Wires in conduit run hotter than wires in free air. Here's a chart that gives ampacity based on THHN insulation and wire installed in conduit. THHN insulated wires can be found at the home center.

Bruce


8-gauge wire is not "pretty small" for a 60 amp load up to a 20' circuit (round trip) on a DC system. The ampacity of #8 wire (other than with an really cheap insulation ) is 80 amps which puts the 60 amp load well within reason if the run is kept within limits.

I did make the assumption that the run would be short (from the battery to the main box) and than we're not talking about bundled wire or run through a conduit with other wires. I should have stated than earlier.

The chart you use is for industrial and commercial AC wiring with raceways; it is not particularly pertinent to DC wiring in a teardrop trailer. For something much closer you might try the wire size calculator at Blue Sea Systems (http://www.blueseasystems.com).
Last edited by Tear Les on Sat Jun 30, 2007 9:15 pm, edited 1 time in total.
Les Lampman
Tear Les
Teardrop Master
 
Posts: 244
Images: 13
Joined: Thu May 17, 2007 9:52 am
Location: Whidbey Island, WA
Top

Postby Tear Les » Sat Jun 30, 2007 9:10 pm

Mike C. wrote:fornesto,

I have sold AC electrical for over 30 years and I would not go less than a #6 gauge, and then I would use welding cable, which is what we sell to manufacturing plants to hook up their battery chargers. If you can't find at Home Depot or Lowe's, go by your local wholesale electrical distributor and most will sell to you for cash.

But the most important question I have is how do you get 60 Amps continuous out of a single battery. What are your loads? And how long do you expect it to run? Are you basing this on your battery, or on the size of your fuse panel?


Mike,

I agree, I would not personally go less than #6 wire for my main feed but it has nothing to do with the electrical requirements of the system; the #8 wire I suggest is more than what is required to meet those needs with a fairly substantial safety margin. I'd use the heavier wire for it's physical poperties including strength and ease of connection.

#6 wire if in free air with decent insulation can safely handle 120 amps for up to a 25-foot round trip circuit; much more, even by conservative standards, than we need here.

I don't do house wiring but since 1971 I've designed, installed, and serviced AC and DC systems on boats with all the attendent U.S. Coast Regulations and ABYC standards. My recommendations always tend to be conservative as I don't like to run close to the limits and I most especially do not want a possibility of personal injury.
Les Lampman
Tear Les
Teardrop Master
 
Posts: 244
Images: 13
Joined: Thu May 17, 2007 9:52 am
Location: Whidbey Island, WA
Top

Postby bdosborn » Sat Jun 30, 2007 10:59 pm

Les,

Using the wire calculator at Blue Sea I get a #3 wire when I applied derating factors such as the wire being buried in foam insulated walls and 60C wire. Stepping up to a 90C wire (THHN) drops it to a #4 as the NEC table recommends. Its a pretty good calculator, the best one I've seen for trailers, thanks for the link. As you mentioned in your post, wire ampacity is dependent on insulation type. A #8 with one type of insulation won't carry the same amount of current as another. What type of insulation do they typically use in marine applications? I posted the NEC chart because it is applicable to wiring that is readily available to most of us (THHN). And you're right, the chart is conservative since it has 25% safety cushion built into it for continuous loads. But since most of the wiring in a teardrop is buried in the walls and it takes so many hours to build one, I tend to lean towards bigger wire sizes.

Bruce
2009 6.5'X11' TTT - Boxcar
Image
Boxcar Build
User avatar
bdosborn
Donating Member
 
Posts: 4175
Images: 450
Joined: Wed May 05, 2004 11:10 pm
Location: CO, Littleton
Top

Postby bledsoe3 » Sun Jul 01, 2007 3:04 am

I used 5 AWG with about a 2' run. I was worried at first and almost went with 2.0. I guess I tend to over build.
If you do what you've always done, you'll get what you've always got.
User avatar
bledsoe3
3000 Club
3000 Club
 
Posts: 3694
Images: 112
Joined: Tue Jun 07, 2005 5:55 am
Location: Oregon, Portland
Top

Postby Tripmaker » Mon Jul 02, 2007 10:09 am

My FIMCO converter charger has a 30 amp fuse and 10 gauge wire for the battery connection. The converter is located in my galley and the battery on the tongue. Although I only run lights and the fantastic fan, and don't expect that I would draw more than 10 amps at any given time on the 12V circuit, I used 8 gauge wire with a 30 amp fuse at the battery end for the 10 foot run from the battery to the converter. Better to be on the safe side.
Jim



I started with nothing and still have most of it left.
User avatar
Tripmaker
500 Club
 
Posts: 869
Images: 59
Joined: Fri Aug 18, 2006 12:09 pm
Location: Fort Wayne, IN
Top

Postby fornesto » Mon Jul 02, 2007 1:57 pm

Whoa, whoa, whoa! Let's clarify a bit. I will have 6 fuses, each rated at 10 amps. Assuming everything is running at the same time (worst case scenario and unlikely) there will be a temporary draw of 10 amps off the battery. Ordinarily, there will be way less than that. I'm talking about a few lights and 12v outlet or two. This wire will be exposed for the most part (run through cabinets).

I think I'll go with 8 guage to the panel and leave the old 110-style wiring in place.
User avatar
fornesto
Donating Member
 
Posts: 765
Joined: Fri Jun 25, 2004 5:12 pm
Location: Carmel Valley, California
Top

Next

Return to Electrical Secrets

Who is online

Users browsing this forum: bsekisser, Trebor English and 2 guests