Alternator wiring to battery

warp2diesel · **Posted:** Sun Feb 17, 2008 11:26 pm

On my old Jetta 1.9 TD (non TDI) I had a bunch of problems with the factory sized conductor between the alternator and the battery. One day I got pissed off and slapped on a 4 gauge cable and had no more problems. With all of the Chrysler bean counter stuff pulled and members reporting dimming lights, I thought I would check their engineering again. Here is a chart showing the recommended size cable for 135 Amps in chassis wiring and it recommends 4 gauge.
http://www.powerstream.com/Wire_Size.htm
Since 4 gauge is a common size for gassers to use for starting circuits, the cable should be easy to com by.
To go one better, I will check out 4 gauge welding cable which has fine wire strands that carry 12 volts even better and have better resistance to fatigue caused by vibration. Solder on ends and heat shrink for strain relief would make it even better :idea:

I will post pics when I get it done.

nursecosmo · **Posted:** Sun Feb 17, 2008 11:32 pm

How many amps do our alternators put out anyway? I have read several conflicting numbers and I can't find it in the FSM.

warp2diesel · **Posted:** Sun Feb 17, 2008 11:38 pm

I ran these figures through the calculator on the web page where I got the info: Copper, 4 AWG, 3 feet, 135 Amps = .207 Voltage drop = 1.72% Voltage drop = 11.793 Volts at end of cable flowing 135 amps.

05infernoCRDL · **Posted:** Sun Feb 17, 2008 11:40 pm

135 for the non renegade...160 for the renegade

nursecosmo · **Posted:** Sun Feb 17, 2008 11:45 pm

Why on earth would they have put a 135 amp in a diesel and 160 in a useless gasser?

warp2diesel · **Posted:** Sun Feb 17, 2008 11:46 pm

With the Renegade putting out 160 the closest in the chart is 158 amps and it recommends 3 AWG. Since 3 AWG (gauge) is not as easy to come by I would go with 2 AWG that would handle 181 Amps. Any idea what size the bean counters picked for the Renegade?
I will gauge the size on mine when I do it.

AbsoluteRenegade · **Posted:** Mon Feb 18, 2008 1:52 am

nursecosmo wrote:

Why on earth would they have put a 135 amp in a diesel and 160 in a useless gasser?

Does the diesel engine need a larger amount of amperage/draw? The Renegade has the larger alternator for the front fogs/lightbar, but I'm not sure it needed it anyways.

05infernoCRDL · **Posted:** Mon Feb 18, 2008 2:03 am

AbsoluteRenegade wrote:

nursecosmo wrote:

Why on earth would they have put a 135 amp in a diesel and 160 in a useless gasser?

Does the diesel engine need a larger amount of amperage/draw? The Renegade has the larger alternator for the front fogs/lightbar, but I'm not sure it needed it anyways.

Diesels don't need more power except for the initial start ,at times. GP (Glow Plugs) put a hefty load on the battery. then the alternator recharges. so 135Amps are fine unless you have a kickin system, or all the lights like the renegade, or a winch, etc.

Gassers have to power spark plugs, that is the only thing i can think of off hand that is more than a diesel engine. Accessories are all subjective.

warp2diesel · **Posted:** Mon Feb 18, 2008 10:55 am

Wires that are overloaded overheat and destroy the insulation; after enough cycles the copper becomes brittle and starts to degrade. Most of the time degrading happens at the end of the wire, where it goes into the connector. When the connection gets bad enough, arcing occurs and finishes destroying the connection. If we have enough wire left on the harness and the connector stud on the alternator is not vaporized, we just cut it off and crimp or solder on a new end.
Bean counters like to make the wires as short as possible and play games with the size of conductor to cut costs. On a starter motor the run time is very short and the conductor does not have enough time to get hot and over heat, when I tested my CRD it drew 300 Amps cold cranking @25f.
Also, bean counters play this game with the charging circuit and hope the battery charges up fast enough to not over heat the alternator to battery wiring.
What will put the most stress on the alternator wiring to the battery is jumping a friends car or truck in cold weather.

cerich · **Posted:** Mon Feb 18, 2008 12:46 pm

what gauge alternator to battery is actually on our CRD's?

warp2diesel · **Posted:** Mon Feb 18, 2008 4:38 pm

cerich wrote:

what gauge alternator to battery is actually on our CRD's?

The Alternator to battery terminal on mine appears to be 6 AWG (gauge) tin platted wire.
The 6 AWG is good for 100 Amps with acceptable losses, not 135 Amps or 160 Amps.
The wire going to the main fuse/relay box looks like a 10 AWG wire.
Since most of our rigs have Optima batteries, don't work in sulfur processing centers, or Waste Water Plant Head Works buildings loaded with H2S gas, a supplemental wire could be added on.
For the Standard 135 Amp alternator adding an additional 12 AWG or 10 AWG wire between the Alternator and battery would be as good as replacing the existing with 4 AWG.
On the Renegade with the 160 Amp Alternator assuming it uses the same harness, 9 AWG or 8 AWG will do the trick.
The 135 Amp alternator uses an 8 mm lug which is a good size, the battery has 6 mm clamp bolts.
Knowing this, my NIX the BEAN COUNTER UPGRADE will be to run 10 AWG to my battery and run another 10 AWG to my fuse/relay, use the best solder on terminal ends, box and apply lots of die-electric paste to the connections :idea:

This addition should keep the wiring between the alternator and battery when I need to jump an old antique.

Steve :wink:

Kniggit · **Posted:** Mon Feb 18, 2008 11:07 pm

warp2diesel wrote:

I ran these figures through the calculator on the web page where I got the info: Copper, 4 AWG, 3 feet, 135 Amps = .207 Voltage drop = 1.72% Voltage drop = 11.793 Volts at end of cable flowing 135 amps.

Actually its closer to 14-1.72%=13.7592 or if you were totally anal 13.8-1.72%=13.52

K

warp2diesel · **Posted:** Tue Feb 19, 2008 12:27 am

....and split hairs on what you plug into a web site calculator (14.5 V vs 12 V), take into consideration that our Liberty CRDs have the voltage regulator in the ECM instead of the alternator. With this feature, the alternator will jack up the voltage until the voltage regulator says it is good enough at the ECM. In theory, it could go as high as 90 volts DC at the alternator so that it can charge the battery. Of course this would produce a lot of heat and do strange things. If the resistance causing the voltage to shoot up would drop quickly enough (like it does when arcing) it would surge and start frying silicone components. Besides, good tight connections and sufficient wire is cheaper than coming up with a 14.5 volt surge suppressor.
In conclusion you can trust the BEAN COUNTERS and help keep their paychecks coming or you can make the resistance between your alternator and battery low and follow industry guidelines and save a few chips in your electronics.
It will it be a few years before the alternator to battery wiring goes bad, of course, the BEAN COUNTERS are counting on it so all of the KJs are out of any extended warranty or potential recall window. Then some Liberty CRD owner will get pissed off like I did at my old Jetta 1.9 TD and throw on a 4 AWG cable to solve the problem.

Alternator wiring to battery

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