Alternator suggestions. 165 Amp?

[l69white]

Hello B-Body friends. I'm new to the forum and did some serching but can't find the information I'm looking for. I'm trying to decide what alternator to purchase for my 1968 Charger build. I'm also looking for information on brackets needed for mounting of any suggestions. If possible I would like to stay with single V belt set up I currently have. Specs. 440 to 512 Stroker, TKX 5 Speed, Sniper 2 EFI, in tank fuel pump, Griffin Rad. with dual electric fans, Dakota Digital dash, Hyper Spark ignition system and finally Vintage Air AC system. I used an online amprage calculator and it recommend 152 Amps. Thank you all for any advice and help.

 

[dadsbee]

Where's that Bob lad when we need him.... lol

What on earth needs 152 amps to keep the battery up to snuff?

 

[65CopCar]

I would be very curious how you came up with 152 amps. That seems very high. Other than the fan, what draws more than 10 amps?

 

[65CopCar]

Where's that Bob lad when we need him.... lol

What on earth needs 152 amps to keep the battery up to snuff?

You beat me to it. LOL!

 

[l69white]

I would be very curious how you came up with 152 amps. That seems very high. Other than the fan, what draws more than 10 amps?

I used this calculator.
Calculate the Amperage You Need

 

[mobileparts]

Dadsbee ,
Helicopters need 200 - 300 Amps for ground starting , but once in flight , they require generally 120 amps for standard operations….
Yours , Craig….

 

[65CopCar]

I used this calculator.
Calculate the Amperage You Need

So sounds like marketing slant to me.

If you list specifically what the rated amperage draw is on your major components we can help you decide what you need.

Remember that the centrifugal devices (like the water pump and fan) amp draws varies with voltage. Centrifugal devices in general follow affinity laws which states that flow is the square of the speed and horsepower is the square of the flow or cube of the speed. The speed of these devices is proportional to the applied voltage. Need to keep this in mind when sizing your charging system.

In addition, when sizing these larger charging systems, cable sizing and cable lugs selection is critical, along with proper fusing.

 

[dadsbee]

Dadsbee ,
Helicopters need 200 - 300 Amps for ground starting , but once in flight , they require generally 120 amps for standard operations….
Yours , Craig….

Must be a big f'n helicopter. Running on mags, once they start they need nothing but enough power to run the radios and nav aids.

 

[l69white]

Ok, so I don't need 152 Amps. Good news. What do y'all suggest then? Would the one attached be sufficient then?

 

[l69white]

So sounds like marketing slant to me.

If you list specifically what the rated amperage draw is on your major components we can help you decide what you need.

Remember that the centrifugal devices (like the water pump and fan) amp draws varies with voltage. Centrifugal devices in general follow affinity laws which states that flow is the square of the speed and horsepower is the square of the flow or cube of the speed. The speed of these devices is proportional to the applied voltage. Need to keep this in mind when sizing your charging system.

In addition, when sizing these larger charging systems, cable sizing and cable lugs selection is critical, along with proper fusing.

That makes sense. I will assess the amp draw for my components and go from there. Thank you.

 

[65CopCar]

Ok, so I don't need 152 Amps. Good news. What do y'all suggest then? Would the one attached be sufficient then?

View attachment 1954247

My rule#1 for buying an alternator is if I can't get an amp versus rpm curve I don't buy it. The amperage rating can be VERY deceptive, especially at low rpm.

 

[l69white]

My rule#1 for buying an alternator is if I can't get an amp versus rpm curve I don't buy it. The amperage rating can be VERY deceptive, especially at low rpm.

I'm clearly out of my depth on this part of my build. Lol. I'll figure it out eventually. Thank you all for the help.

 

[65CopCar]

I'm clearly out of my depth on this part of my build. Lol. I'll figure it out eventually. Thank you all for the help.

Give this a quick read. Its pretty simple - at low rpms, the alternator puts out a lot less amps than at higher rpms. The rated alternator amps gives very little information on how many amps the alternator will actually put out at the rpms where it matters. Quality alternators do better at low rpms than cheap ones.

Quality alternator vendors will provide this information, sometimes you ave to ask for it.

Electrical Load Verses Alternator Performance - Power Curve - TECHNICAL

 

[radical rob]

call John at Powermaster. They can help. I run the biggest on they. Are and it bolts right in with stock brackets. Think max is 175 amp

 

[dadsbee]

Run what ever you want, just remember that no matter how big it is, it will only put out the amperage needed PROVIDED THAT THINGS ARE WIRED CORRECTLY. Jesus, I think Bob jumped into me like some horror movie...

 

[Unkle Krusty]

I thought 100 amps was when you needed two belts to drive it. I replaced the stock unit on my camper van, and do not know what amperage it is. Somewhere between 55 and 75 I would guess. On the boat where lots of stuff is running the alternator is 55 amps. I think it is advisable to run a smart regulator outside the alternator for larger amps.
I cannot think of any need for more than 75 amps. And follow the advice above for charging rates.