Battery cable wire gauge

[El.Padrino]

What size wire is the smaller red battery+ wire that goes to the post on the starter relay? 1968 B body noA/C big block, auto

Thank you!

 

[hunt2elk]

The last 2 cables I got had a red #8, but the service manual shows it as being a #10 from the factory.

 

[El.Padrino]

The last 2 cables I got had a red #8, but the service manual shows it as being a #10 from the factory.

so #10 should be safe

 

[hunt2elk]

so #10 should be safe

I would think so.

 

[69Bee]

I would stick with the 8AWG or 6AWG. A 10AWG wire is spec'd for only 30A, which is why so many ammeter wiring setups burnt up. The wire is too small. I do believe that the brown wire to the starter relay is 10AWG though, but it doesn't handle a lot of current.

 

[hunt2elk]

I do believe that the brown wire to the starter relay is 10AWG though, but it doesn't handle a lot of current.

Yeah, that #10 is the wire the op is asking about.

 

[69Bee]

Yeah, that #10 is the wire the op is asking about.

You are correct, I missed that. Thanks...

 

[RJRENTON]

I would stick with the 8AWG or 6AWG. A 10AWG wire is spec'd for only 30A, which is why so many ammeter wiring setups burnt up. The wire is too small. I do believe that the brown wire to the starter relay is 10AWG though, but it doesn't handle a lot of current.

The AMPACITY (amp capacity) of the wire's is determined by the National Electrical Code (NEC) and the use intended, according to the insulation system used (THHN, THWN, XLP, RHW, PTFE, etc) which is determined by the maximum ambient temperature anticipated and whether the wire in in open air or in conduit. When in doubt, it is better to have more ampacity than kess and to use an insulation system that exceeds the maximum ambient temperature anticipated. Since the voltage level is low (12 volts) all of the insulation system noted is 600 volts, select the insulation system that is the most economical....suggest THHN (105° C). IF the ambient temp is exceeded, the wire must be de-rated for amps....the higher the temperature reduce the amps. Suggest reviewing the latest edition of the NEC when in doubt. Just a few additional points to ponder......
BOB RENTON

 

[69Bee]

The AMPACITY (amp capacity) of the wire's is determined by the National Electrical Code (NEC) and the use intended, according to the insulation system used (THHN, THWN, XLP, RHW, PTFE, etc) which is determined by the maximum ambient temperature anticipated and whether the wire in in open air or in conduit. When in doubt, it is better to have more ampacity than kess and to use an insulation system that exceeds the maximum ambient temperature anticipated. Since the voltage level is low (12 volts) all of the insulation system noted is 600 volts, select the insulation system that is the most economical....suggest THHN (105° C). IF the ambient temp is exceeded, the wire must be de-rated for amps....the higher the temperature reduce the amps. Suggest reviewing the latest edition of the NEC when in doubt. Just a few additional points to ponder......
BOB RENTON

Seriously?? He is working on a car for crying out loud, not building the space shuttle or having to deal with building codes. I know what you are talking about, attempting to look smart and all, seeing as how I do have a BSEET after my name if I wanted to look cool and all!!

 

[RJRENTON]

Seriously?? He is working on a car for crying out loud, not building the space shuttle or having to deal with building codes. I know what you are talking about, attempting to look smart and all, seeing as how I do have a BSEET after my name if I wanted to look cool and all!!

A BSEET is good but its not the same as BSEE and combined with a Professional Electrical Engineer credential which brings ethics and economics into the equation.....by doing things the "right" or "correct" way. Exactly what is your objection to using an established criteria...an opinion or understanding or both? We're not talking about building a space shuttle, which subscribes to similar, if not more stringent criteria, but providing the OP additional information to make an decision based on aaccurate information. Since you seem to object to my criteria, perhaps, you would like to enlighten me and the other readers of this thread, what you would recommend.....I'm always interested in learning more about a subject. Just my opinion.....
BOB RENTON

 

[Nacho-RT74]

I would stick with the 8AWG or 6AWG. A 10AWG wire is spec'd for only 30A, which is why so many ammeter wiring setups burnt up. The wire is too small. I do believe that the brown wire to the starter relay is 10AWG though, but it doesn't handle a lot of current.

That's not the reason actually the amm tends to fail. There are more imprtant reasons like the underrated alts from fact. But that's another discussion.

And, is true as you mentioned factory used 10 AWG wire which could be plenty for stock setup with a good alt able to supply all the power demand at the minimum rpms as posible ( iddle if posible ). Reinforce the wire between alt and amm AND with a powerfull alt is more protective to all the charging system, amm included.

 

[Old Sparky]

What size wire is the smaller red battery+ wire that goes to the post on the starter relay? 1968 B body noA/C big block, auto

Thank you!

#10

 

[Don Frelier]

Well he is in Austria, so if anything he would refer to the IEC standard.
I think 90 Deg. C wire would be fine so something like MTW wire would be my choice.
And I would consider the conductor to be in free air so the allowable ampacity would be higher than the 30 amp value stated above.

 

[451Mopar]

The AMPACITY (amp capacity) of the wire's is determined by the National Electrical Code (NEC) and the use intended, according to the insulation system used (THHN, THWN, XLP, RHW, PTFE, etc) which is determined by the maximum ambient temperature anticipated and whether the wire in in open air or in conduit. When in doubt, it is better to have more ampacity than kess and to use an insulation system that exceeds the maximum ambient temperature anticipated. Since the voltage level is low (12 volts) all of the insulation system noted is 600 volts, select the insulation system that is the most economical....suggest THHN (105° C). IF the ambient temp is exceeded, the wire must be de-rated for amps....the higher the temperature reduce the amps. Suggest reviewing the latest edition of the NEC when in doubt. Just a few additional points to ponder......
BOB RENTON

THHN might be the cheapest, only AWM 1316 to 1321 is rated 105° C, most is just 90° C. It is also PVC insulation (melts when hot)
XLPE wire (SAE J-1128) is pretty much the automotive standard. Temps from -51° C to 125° C.
The difference between the TXL, GXL, SXL is the insulation thickness. TXL is the "Extra Thin Wall" version normally seen in modern cars where the wires are protected in a harness. GXL is "Standard Wall" version, and the insulation thickness is close to the original PVC wired of the old cars, so it makes a nice replacement. The SXL is "Heavy Wall" insulation version usually used then the wire is run outside a harness like from Battery to Relay.
The cost of the (T/G/S)XL wire is not that much more than PVC hookup wire. This wire spec is only rated to 60 Volts. That is fine in Car, but don't use as household wiring.
There are UL AWM rated version of XLPE wire rate at higher voltages like 600 volts.

The starter solenoid to NSS relay wire that run close to the exhaust is normally a high temperature silicone insulated wire.

 

[1STMP]

Seriously?? He is working on a car for crying out loud, not building the space shuttle or having to deal with building codes. I know what you are talking about, attempting to look smart and all, seeing as how I do have a BSEET after my name if I wanted to look cool and all!!

Bob is a straight shooter and has helped many
here solve their issues. He's not very often
incorrect. Seriously.

 

[RJRENTON]

Bob is a straight shooter and has helped many
here solve their issues. He's not very often
incorrect. Seriously.

THANK YOU for your testimonial.....I guess there are always people that will disagree on any subject but do not offer any optional information or thoughts of their own.....its sort of like restating the old ALCOA's NIH (Not Invented Here) rule, where any idea presented is wrong, because it wasn't thought of by ALCOA (Aluminum Company of America) first. And, yes....unfortunately I sometimes get it wrong with my opinion or information, but..."to err is human but to forgive is Devine"......
BOB RENTON

 

[Old Sparky]

I would stick with the 8AWG or 6AWG. A 10AWG wire is spec'd for only 30A, which is why so many ammeter wiring setups burnt up. The wire is too small. I do believe that the brown wire to the starter relay is 10AWG though, but it doesn't handle a lot of current.

The small wire to the starter is #14. the large red from the alternator is #10....#10 in a 12v system carries much closer to 60A or more but I limit it to 60....you have to consider it as a total wattage system. The small wire to the solenoid on the starter only runs the solenoid....the large #3 or #4 or #6 (depending on engine), from the battery does all the work.

 

[69Bee]

The small wire to the starter is #14. the large red from the alternator is #10....#10 in a 12v system carries much closer to 60A or more but I limit it to 60....you have to consider it as a total wattage system. The small wire to the solenoid on the starter only runs the solenoid....the large #3 or #4 or #6 (depending on engine), from the battery does all the work.

Sorry, but that is incorrect. The red wire to the starter relay "BAT" terminal is 10Awg and the red wire to the starter is 6Awg. The brown wire from the starter relay "Sol" terminal to the starter solenoid is 12awg. The starter relay "I" terminal goes to the ignition switch and is 18Awg. The starter relay "G" terminal is soldered to the relay can for a manual and an automatic has a terminal for a brown wire to the neutral safety switch, also 18Awg. The manual shows the starter solenoid will draw 8-9A @ 6v, which gives approximately 700mOhm for the coil. 12v/0.7= 17.4A and the 12Awg wire is rated at 20A. All of this disregards the resistance of the wire for simplicity. The wire from the battery to the "BAT" terminal on the starter relay has a 12Awg fusible link, so basically, there is no way that wire operates or can even handle 60A...

 

[Davefinan]

Hey Bob I must say , that was an excellent explanation of the ampacity of wire. I am a retired electrician of 42 years and I probably haven’t heard it explained in that detail since apprentice school. Kudos!

 

[RJRENTON]

Hey Bob I must say , that was an excellent explanation of the ampacity of wire. I am a retired electrician of 42 years and I probably haven’t heard it explained in that detail since apprentice school. Kudos!

THANK YOU FOR YOUR KIND WORDS.....they are very much appreciated. Best wishes for the up coming holiday season.....hope Santa Claus brings you many things.....
BOB RENTON