Battery Cable Question

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Model T Ford Forum: Forum 2013: Battery Cable Question
Top of pagePrevious messageNext messageBottom of page Link to this message  By Dave Barker - Dayton, OH on Friday, August 30, 2013 - 03:14 pm:

Replacing the battery cables in a 1919 Speedster. 6V battery with a generator and distributor, but no starter and no magneto. It previously had two 12 gauge wires as the battery cable, both ran from the battery to the terminal block.

I'm good with the ground strap, but what's the recommendation for the battery to terminal wire size? I want to replace the two 12 gauge wires with a single wire. Thanks.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Cary Abate on Friday, August 30, 2013 - 03:44 pm:

2 - #12 = 18.6 amps

1 - #8 =. 24 amps

1 - #6 = 37 amps

Inline fuse of 20 amps or 25 to lights and etc

Bigger is better. Smaller is not good.

C Abate retired


Top of pagePrevious messageNext messageBottom of page Link to this message  By Cary Abate on Friday, August 30, 2013 - 03:54 pm:

Actually see http://www.mtfca.com/discus/messages/331880/385312.html?1377889742 for suggestion on cable size


Top of pagePrevious messageNext messageBottom of page Link to this message  By Dave Barker - Dayton, OH on Friday, August 30, 2013 - 03:59 pm:

Thanks Cary, I saw the other post and was following it. Didn't know if I need that large of a cable, as I'm not using a starter. From your list, I would think one 6 gauge connection should work, correct?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Cary Abate on Friday, August 30, 2013 - 04:21 pm:

Dave,

As long as you are changing use the directions from the other post and be done with it. Remember the lower the voltage the higher the current. 6 v amps are twice what 12 volt are. The smaller wire generates more heat. Go big.

Smoke is to be avoided in your T.

Cary


Top of pagePrevious messageNext messageBottom of page Link to this message  By Roger Gooding, Crystal, MI on Friday, August 30, 2013 - 06:32 pm:

My understanding is you want to go from the battery to the terminal block. If my memory is right, that wire is one 12 gauge wire. If it is bigger, it is no bigger than 10 gauge.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ken Kopsky, Lytle TX on Friday, August 30, 2013 - 06:38 pm:

Ditto on the #12. Nothing more is needed if you don't have a starter. The original "battery" circuit was #12 from about 1920 and up. The BIG cable is for the starter circuit only.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Dave Barker - Dayton, OH on Friday, August 30, 2013 - 10:32 pm:

Thanks all. Much appreciated.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Dave Barker - Dayton, OH on Friday, August 30, 2013 - 10:34 pm:

By the way, I already have the fuse kit from Fun Projects, which will be installed as well. Thanks again.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ken Todd on Sunday, September 01, 2013 - 12:18 pm:

Cary, where did you get your amperage ratings for wires from?
In my world one #12 is good for 20 amps, so 2 in parallel should be good for 40 amps.
Also (in my world) #8 is good for 40 amps and #6 is good for 60 amps.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mike D, Williamsburg VA on Sunday, September 01, 2013 - 12:51 pm:

This might help


Top of pagePrevious messageNext messageBottom of page Link to this message  By James A. Golden on Monday, September 02, 2013 - 08:16 am:

I recently ordered some battery terminals for 1/0 and 2/0 cable.

They were advertised as solder on terminals, but the fine print on each terminal notes they are crimp on terminals.

The company apparently does not offer the solder slugs that makes the soldering job rather easy.

I'm wondering if there is any real difference in the two larger size cable terminal types.


Top of pagePrevious messageNext messageBottom of page Link to this message  By James A. Golden on Monday, September 02, 2013 - 09:49 am:

This chart will add some more numbers to the the above photo.

Another chart posted here a few years ago by Ron "Coilman" Patterson showed the starter current at 400 amps when the switch was first depressed and then rapidly dropping off to about 275 amps.

That level might still be 300 amps with a high compression head or other engine modifications.

That scenario makes a 2 gauge cable less than adequate for Model T vehicles with a starter installed.

The below figures are from a standard chart used by several electrical societies.

Note that the 00 gauge cable is half again as large and offers half again as much current as a 2 gauge cable.

Wire Gauge--Diameter Inches---Max Amps
00-------------0.3648-----------283
0--------------0.3249-----------245
1--------------0.2893-----------211
2--------------0.2576-----------181


Top of pagePrevious messageNext messageBottom of page Link to this message  By George_Cherry Hill NJ on Monday, September 02, 2013 - 10:29 am:

Jim,

I agree with what you say as to published data. FWIW, My next project I plan on going to '00' on anything in the future and tentatively plan on having them made by YnZ. I say tentative as I looked into making them up myself as soldered...and YnZ price complete/soldered/clothed/correct lugs is about the same as my own cost to just buy correct era style components for a couple of times each is.)

Yeah, '0' would also be a vast improvement, but the price difference from YnZ for the next size up wire and lugs is only about $15 bucks once you get over the initial sticker shock anyway.

I do think however, that looking at amps alone is not the sole criteria. Those published charts are based on continuous duty, and if you have to crank a T with a starter for more than 15-30 seconds you have bigger problems. I based my own view on the voltage drop criteria as being primary. While I do not advocate using the concept for sizing...do the old E=I*R and you'd be amazed at how much short burst amps can be handled before you have to worry about that heat factor which is what 'continuos' is sized on in those tables.

Lots of anecdotal experience says that a T starter motor just doesn't have any break-away guts on a good compression motor once the voltage drop is about .75-1.00 of a volt or so. The original switches get gunky and corroded inside...the repro switches are said to be junk as to contact surface...there are those that just bolt lugs up without polishing and using contact clean...(and some who think a #2 is OK!) What do all of these symptoms have in common? VOLTAGE DROP! The strongest 6V battery in the world may not be able to pump enough voltage through for the starter to develop torque due to the losses.

I'm not saying that going to '00' is the cure-all to end all, I have always and still will carry spare starter switches (2) in my starter equipped cars and 1 ou. can of spray 'De-ox' contact clean...but my thought is just going to '00' takes the voltage drop per foot out of the equation for a little extra. Yeah, the $$$$ make you wheeze for these large size wires..but you only do it once per car :-)


Top of pagePrevious messageNext messageBottom of page Link to this message  By Cary Abate on Monday, September 02, 2013 - 10:36 am:

Ken,

Regarding the #12 this should have been each in as much as the replacement was to be one wire. As far as the amounts are concerned I use very conservative figures. 6 volt circuits on old cars are subject to severe corrosion on the connectors therefor I prefer to avoid voltage drops that raise currents and are hard on old starters and generators.

Thanks for catching my error.


Cary


Top of pagePrevious messageNext messageBottom of page Link to this message  By ROBERT J STEINER on Monday, September 02, 2013 - 11:01 am:

RJ&L wiring has 00 braided battery cable terminals and tinned copper lugs ready to go already made up


Top of pagePrevious messageNext messageBottom of page Link to this message  By ROBERT J STEINER on Monday, September 02, 2013 - 11:04 am:

Sorry guys ...you are talking primary wire sizes. I was refering to cables size.. there is 2 forums on this subject


Top of pagePrevious messageNext messageBottom of page Link to this message  By Rick Goelz-Knoxville,TN on Monday, September 02, 2013 - 11:27 am:

remember that the wire/amp charts show the values for 100' or on smaller wires 1000' so if it shows 400 amps at 100' and you are only running the wire 6' you have 94% of the capacity in your 6', i think this is correct it has been a long time since i had to fool with this.

Rick


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