Alternator wiring mod.

[bbeep71]

I want to make the Allpar.com mod to the alt. that runs a new bat wire(alt) to the starter relay batt terminal. This allows the alt to charge directly to the batt and takes some stress off the bulkhead connector. The car is a 66 Cuda. I don't know what the alt output is. It looks like a mopar stock roundback alt. My question is what type of fusing I should provide for that wire (8 awg) to the starter relay? Should I use a fusible link (what size link) or circuit breaker(what size). I have a 80 amp circuit breaker to use if that would do the job.
Thanks

 

[RedFish]

Your round back alternater is rated at forty something amps at most. Those were 36 and 42 or 38 and 46, I forget.

 

[Oldmanmopar]

The alternator I used is 100 amps.One wire 6 inches long no fuse. It is the short black wire going to the Pos. battery bulk head in the pic. I use this bulk head under the hood because my battery is in the trunk. Otherwise it would go right to the battery.

 

[Bulldozer]

.......

 

[bbeep71]

Thanks Guys for your reply. I decided to use a 50amp circuit breaker in line with the alt. wire.

 

[67Dart273]

Thanks Guys for your reply. I decided to use a 50amp circuit breaker in line with the alt. wire.

Personally, I would not. If that breaker ever pops open because of a combination of engine heat (heat degrades the amperage), and heavily charging, then the alternator will create a huge voltage spike. The alternator voltage can go WAY out of sight instantaneously, and this may very well cause a cycling effect, IE the breaker tripping several times.

The more electronics you have in the car, the more danger you have of "killing" something.

 

[bbeep71]

Hi,
The breaker I'm going to use is a Type 3 which opens and stays open until you manually reset it. I am leaving the original alt wire to the bulk connector in place? What would you suggest to protect the alt.?

 

[wjajr]

The whole point of the bypass is to limit flow of electrons through bulkhead connector, this is why the black wire from alternator to bulkhead connector is relocated and landed on starter relay’s threaded stud connecting it directly to battery, not bulkhead connector.

If you examine Madd’s diagram, it illustrates how Chrysler’s charging circuit flows electrons in two directions through bulkhead connector depending if battery or alternator is supplying current. You can see that under certain conditions battery can be sole current supply source, and conversely alternator a single supplier when battery is discharged.

The bypass accomplishes two things: now all charging current is directly feed to battery bypassing the dash and other circuits south of the fire wall protecting bulkhead connector from over current; secondly battery is able to absorb much more current than the alternator can put out short term before some sort of current interruption device kicks in to open circuit.

Alternator can produce up to its full rating, perhaps a bit more depending on conditions be it 35 amps or 100 amps, on the other hand as much as a 1000 amps may be available depending on size of battery installed. The battery is the big current gorilla in the room.

So to answer your question:

I am leaving the original alt wire to the bulk connector in place?

No, you are replacing that 10 gage black wire with a thicker gage conductor perhaps two 10 AWG*, or one 6 AWG between alternator, and starter relay. Also be sure to have a large enough conductor connecting starter relay’s threaded stud and + battery terminal to carry the increased load.

*
Personally I’m not a fan of parallel conductors they can be problematic if one conductor were to fail for whatever reason.

 

[BillGrissom]

If a small block, I would run the wire straight to the battery, across the timing cover. I used the cable off a Magnum motor since they did that. I installed a 180 A fuse. That gives little risk of failing wrongly but may still protect for a dead short. I don't recall that Magnum wiring even has a fuse. If electrically savy, lookup my post on how I used parallel diodes to make this path a shunt when needed (>0.5 V drop), while normally it still flows thru the ammeter so that works.