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Old 03-07-2019, 11:43 AM   #1
Join Date: Jan 2019
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High Output Alternator Upgrade - Has anyone done this?

I am new owner of a 40C with the Cummins 380 and I am holistically looking at power systems. Being an EE this is my first intrigue with the rig..

As I look at Batteries, Charging, Generation, Inverting & Consumption I am thinking one of lynch pins is the Alternator.

The stock alternator is 160 Amps which is fine. But I would like to be able run House AC units as I am driving without running the 10K Generator.

I have done some research and there are high-output Alternators in the 300+ Amp range..

I have not been able to find the make and model of the current alternator - Does anyone know what it is?

Has anyone installed a Hi Output Alternator?

Thanks in advance...

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Old 03-07-2019, 11:59 AM   #2
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An RV A/C would need 177 amps at 12 volt DC thru an inverter. That is just for the A/C. That is a lot of amps.

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Old 03-07-2019, 12:00 PM   #3
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Old 03-07-2019, 12:10 PM   #4
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Air Conditioning Power Consumption

I just did the math (worst case):
The AC unit is on a 15 Amp circuit
120VAC * 15 Amps = 1800 Watts AC

Converting that to DC:
1800W/12VDC = 150 Amps DC

Granted the efficiencies of the inverter will not be 100% but this is close...

My thinking, all things being equal, by upgrading from a 160 A alternator to a 340 alternator I have about 200 extra amps...
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Old 03-07-2019, 12:16 PM   #5
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you can look and see if your chassis was ever available with a twin alternator setup. this is fairly common in the car audio world and with ambulance packages.
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Old 03-07-2019, 12:30 PM   #6
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Beat me to it.

Common on boats as well.

Alternators in trucks and cars don't power much. AC is engine powered for example. Audio, medical equipment, and marine electronics suck up a lot of current. Alternators seem to work best at no more than half their rated maximum power outputs.

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Old 03-07-2019, 01:01 PM   #7
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I'm sure there's a 350A alternator out there for that engine. I would contact Freightliner Custom Chassis Corporation to find the exact details of what the integration of a 350 amp alternator entails.
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Old 03-07-2019, 02:04 PM   #8
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Do you think that would be a good idea . As converting back to 120 volts from 12 volts DC . You lose about 30% doing that . Do you think it would be worth the money .
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Old 03-07-2019, 02:17 PM   #9
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LOL - not sure if it is a good idea....

I am planning on significantly upgrading the batteries to LiFePO4.. At a minimum 8 batteries, for 800 AH of stored power.

But that means I can also charge at 800 Amps per hour..

Having a high-output alternator will allow me charge much faster as well...

Using the same math (w/o the AC being turned on), I could use the extra 200 Amps to charge the entire battery bank in 4 hours of drive time.
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Old 03-07-2019, 02:20 PM   #10
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oh, then I should be able to run an AC unit for about 5 hours

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