12v battery/starter cable

zeke57 · Post by **zeke57** » Fri Jun 14, 2019 3:20 pm

Before I purchase cables I am looking for some input from those of you who have converted your a1 to 12v. Is 4 gauge sufficient or should I use 2 ? Next thing I am wondering about is cable length. Being that I will be installing one battery in the stock location I have to decide which battery tray to use so I figured I would use the one furthest from the engine. I see the original cables were 42''(-) and 25''(+). So in my configuration would I be safe to use the 42'' negative and just get a longer positive cable say 38'' or should I use the tray closer to the engine and use a longer negative cable and the stock length positive cable?

4x4M38 · Post by **4x4M38** » Fri Jun 14, 2019 6:23 pm

If you are going 12v I would use the engine compartment location.
The cable to the starter is short enough, and the ground cable
even shorter.

Just my two cents.

zeke57 · Post by **zeke57** » Fri Jun 14, 2019 6:30 pm

So do you think it is not a good idea to mount the battery in the stock location? I would like to put it there as long as the extra long cables will not be an issue.

mdainsd · Post by **mdainsd** » Fri Jun 14, 2019 7:17 pm

Sounds like the usual issue: What type Jeep are we talking about? It sounds like the OP is talking about an A1

Post by **wesk** » Fri Jun 14, 2019 10:49 pm

1 - Zeke57 is talking about his M38A1.

2 - Brian, The M38A1 does not have an underhood battery box. It has a double battery box in the cowl.

3 - The military battery cable were overkill on the M38A1 and will handle the 12 volts just fine.

4 - Put the battery in the far left (closest to the driver) tray. Use the original stock M38A1 battery + to starter cable. The 25" pos cable and 42" neg cable will fit just fine.

zeke57 · Post by **zeke57** » Sat Jun 15, 2019 5:27 am

If I use the bat. tray recommended I would have to drill a new hole in the fire wall to accommodate the stock 42'' ground cable so I am going to just purchase a longer cable so I can rout it through the original hole and then down to the frame. One other thing should I use 4 gauge cable or #2 ?

Post by **wesk** » Sat Jun 15, 2019 7:50 am

Read the details closer on my illustration. The stock 42" cable stays inside the battery box to the bottom and then comes out the rt side drain tube hole. It should still reach the ground bolt on the regulator tray with ease.

zeke57 · Post by **zeke57** » Sat Jun 15, 2019 10:50 am

I guess I need to read things more closely before I reply have to work on that. Thanks for pointing that out to me Wes I was just assuming a new hole was punched. As for cable gauge 2 or 4 ? Thanks.

Post by **wesk** » Sat Jun 15, 2019 11:20 am

As I posted above:

3 - The military battery cable were overkill on the M38A1 and will handle the 12 volts just fine.

Those original cables will work just fine on 12 volt. If you insist on new cable then use the standard used today for 12V which is based on amps per foot voltage drop rates:

Battery Cable Amperage Capacity Chart
Recommended Length and Amperage for Battery Cable while maintaining a 2% or less voltage drop at 12 volts
Battery Cable Size 50 Amps 100 Amps 150 Amps 200 Amps 300 Amps
6 Gauge (AWG) 11.8 ft 5.9 ft 4.4 ft 2.9 ft 2.2 ft
4 Gauge (AWG) 18.8 ft 9.4 ft 6.3 ft 4.7 ft 3.1 ft
2 Gauge (AWG) 29.8 ft 14.9 ft 9.9 ft 7.4 ft 4.9 ft
1 Gauge (AWG) 37.7 ft 18.9 ft 12.6 ft 9.4 ft 6.3 ft
1/0 Gauge (AWG) 47.5 ft 23.8 ft 15.9 ft 11.9 ft 7.9 ft
2/0 Gauge (AWG) 60 ft 30 ft 20 ft 15 ft 10 ft
3/0 Gauge (AWG) 75.6 ft 37.8 ft 25.2 ft 18.9 ft 12.6 ft
4/0 Gauge (AWG) 95.2 ft 47.6 ft 31.7 ft 23.8 ft 15.8 ft.

Check out this link: https://www.wiringproducts.com/battery-cable

zeke57 · Post by **zeke57** » Sat Jun 15, 2019 12:01 pm

My original cables are shot that is why I need new. So looking at the above chart based on a 65 amp system I could theoretically use a 6 gauge cable. I spoke with a vendor who recommended 2 gauge. I trust your opinion more than the vendor Wes so if you were me what would you use? Thanks.

Post by **wesk** » Sat Jun 15, 2019 10:04 pm

The system amperage referred to in the chart is the total current draw the cables will be exposed to and not the amperage rating of the alternator. This means you must tally up the maximum expected current draw of each and every component in your jeeps electrical system. This includes the stall amperage of your starter, the combined current draw of all lamps, horn, gauges, ignition system and etc. Then you must determine what the maximum current is that you can expect from the maximum # of components that you think may be operating at the same time. That amperage or the highest individual component amperage, whichever is greater is the Number you use to choose the correct gauge cable considering the lengths you will need. I know it's a lot of research but it is necessary when you take off down the road to more modifications from stock.