If replacing alternator, which amperage?

[koosh]

If stock alternator on big block 68 Charger needs replacing, what should i be looking for amperage wise? I dont want to “cook” wires-seems like most new are 100 amps or so.
I assume i need one for external regulator?

 

[zyzzyx]

Get a 60A Denso and the bracket kit from Mancini. No more charging problems at idle. Internal regulator too!

 

[1968rt]

Just changed mine in my 68. I went with a 60 amp stock type replacement.

 

[Don Frelier]

If you want an upgrade I would suggest getting a 60 amp from any 70's chrysler product.
Get a solid state voltage regulator and a replacement plug for it.
You just need to run one wire from the plug to the alternator for a dual field setup.
All this is available from RockAuto.
This is what I have in both my cars.

Or just rebuild/replace your existing alternator.

 

[Photon440]

If stock alternator on big block 68 Charger needs replacing, what should i be looking for amperage wise? I dont want to “cook” wires-seems like most new are 100 amps or so.
I assume i need one for external regulator?

You won't 'cook' your wires with a higher amp alternator, it will still only put out what is required. Just like if you had a 60 amp home service breaker box in your house and upgraded it to a 200 amp box, your wires wouldn't get any warmer.

 

[Don Frelier]

You won't 'cook' your wires with a higher amp alternator, it will still only put out what is required. Just like if you had a 60 amp home service breaker box in your house and upgraded it to a 200 amp box, your wires wouldn't get any warmer.

Except when you're battery is partly drained.
It's not an apples to apples with a home service.

 

[Photon440]

Except when you're battery is partly drained.
It's not an apples to apples with a home service.

Well, alternators aren't meant to charge drained batteries, that's what battery chargers are for. I worked in a parts store and know that some alternator warranties are voided if you use them to charge a drained battery. They're intended to maintain a charged battery. However, the strain on the alternator with a discharged battery is less if it is rated at a higher output.

 

[koosh]

I found a Powermaster with this description:
“

• 100 Plus Amps At Top End/65 Plus Amps At Idle

 

[Don Frelier]

Well, alternators aren't meant to charge drained batteries, that's what battery chargers are for. I worked in a parts store and know that some alternator warranties are voided if you use them to charge a drained battery. They're intended to maintain a charged battery. However, the strain on the alternator with a discharged battery is less if it is rated at a higher output.

There are plenty of scenarios where the battery gets partly drained (while your not home)
- You go to dinner or somewhere and leave the lights on by accident
- For any of several reasons something goes wrong and you need to crank it over way more than usual

Please explain your last sentence?
His concern for the existing wiring is a valid consideration.

 

[Photon440]

There are plenty of scenarios where the battery gets partly drained (while your not home)
- You go to dinner or somewhere and leave the lights on by accident
- For any of several reasons something goes wrong and you need to crank it over way more than usual

Please explain your last sentence?
His concern for the existing wiring is a valid consideration.

When I mentioned that "However, the strain on the alternator with a discharged battery is less if it is rated at a higher output." it simply means that if a heavily discharged battery is drawing a lot of amperage, it will be harder on a smaller alternator that may be maxed out to provide that current flow, as compared to a more robust alternator that has plenty of additional reserve capacity.

As for the wiring, the lighting, accessories and other power drains are pulling from the battery, which itself will provide far more amps than the alternator itself. The alternator, however large, it just topping up that battery.

 

[koosh]

Does-
“

• 100 Plus Amps At Top End/65 Plus Amps At Idle

Sound ok/safe to use?

 

[Don Frelier]

When I mentioned that "However, the strain on the alternator with a discharged battery is less if it is rated at a higher output." it simply means that if a heavily discharged battery is drawing a lot of amperage, it will be harder on a smaller alternator that may be maxed out to provide that current flow, as compared to a more robust alternator that has plenty of additional reserve capacity.

As for the wiring, the lighting, accessories and other power drains are pulling from the battery, which itself will provide far more amps than the alternator itself. The alternator, however large, it just topping up that battery.

I would still contend that putting a 100 amp alternator on an old car that originally came with a 38 amp has the potential to speed up the degradation of the old wires and connectors.

I don't disagree that when you have a fully charged battery it would work well.

Perhaps I should have stated that earlier.

 

[zyzzyx]

If you don't need all that juice to run fans, lights, electric pumps, Etc., why? 60A is enough for a stocker.

 

[Don Frelier]

If you don't need all that juice to run fans, lights, electric pumps, Etc., why? 60A is enough for a stocker.

The original was 38 Amps

 

[Nacho-RT74]

If you don't need all that juice to run fans, lights, electric pumps, Etc., why? 60A is enough for a stocker.

The problem with 60 amps alt is they still barelly puts 30-35 at iddle. Now, turn on your AC/Heater blower at max speed and will see how you can’t raise up the discharge status at idle. Then turn on lights because you are at night… then imagine is raining too and turn on wipers… now give brakes because you are stopped at a traffic light… and you are with radio on.


You’ll see the battery being heavily drained. Now give gas to move the car… high rates recharge status for some time.

The you wonder why is very tipical get burnt wiring on the original charging network

Still with a 60 amps Chrysler alt.


So… the best in MY opinion, get an alt able to give no less than 45-55 amps (depending on options) AT IDLE. If more… BETTER. Enough to keep the car running with zero reading in amm as much as posible and you will save the continuous charge/discharge flow.

If you car demands for 40 amps at certain stage no matter if your alt is able to source 65 amps at iddle, the car will suck JUST those 40 and the rest won’t be requested.

Amps are not pushed in by the power source but sucked out by the accs.

The same batt able to move the starter motor through a 4 or 2 gauge wire, turns on the light for the ashtray on a 18 gauge wire. And the big batt power source doesn’t burn the bulb or the wire for it.

(Soon… Some A$$ho13 around saying to forget this post #15 because blah blah blah in 5… 4… 3… 2… )


EDITING… 60 amps Denso alt is a diff toy and is able to source more than the stock units at idle thought

 

[dadsbee]

How did we ever survive coming home from the drive-in at 3am.. pouring rain and fully in the bag?

 

[koosh]

I guess my post 11, that 60-100 would suffice

 

[dadsbee]

Do you even drive it at night? OE has worked for 56 years....

 

[zyzzyx]

The problem with the factory alternators is that they don't charge well at idle. The Denso charges really well at idle, that's
why so many put them on their cars, and they last forever. Also, they have an internal regulator.

 

[Nacho-RT74]

LOL, just edited my reply talking about the diff Denso alt capacities at idle… which is true HOWEVER, I think more is better.