I have a 2019 F450 King Ranch that I use to tow a 5th wheel. I'd like to put in DC-DC charging between the truck and RV and am trying to figure out if I should upgrade the alternator or if the stock unit will be able to keep up with the load I'm going to place on it.

I'm going to put 120 amps of DC-DC charging into the RV and will connect straight to the battery (or alternator) on the truck with 2/0 wire (which should be good for around 150A) via an Anderson plug with the 2/0 continuing to the RV and into the DC-DC converters. The stock 67D "Extra Heavy Duty" alternator on the truck is rated for 220A, but... Is it really able to do that much? And if so, can it do it for hours at a time?

If not, I'm considering upgrading to something like this:
https://www.mechman.com/alternators/...d-6-7l-diesel/

Anyone do something like this and have any feedback/suggestions/experience to offer? My goal is to be able to run an AC unit in the RV when we travel without using the generator; 120A of DC should be enough to do that indefinately, but the load could be relatively constant on the alternator (the AC might run continuously in hot weather).

Thank you!

 

I've looked at doing that as well, because well, I'm overkill... But for someone like you who would actually have the use for a bigger alternator, it would be worth looking into. The alternators in our trucks now are the small case alternators. In using the alternator to it's potential, the large case would handle the heat better than the smaller case alternator... I think I've read they stopped using the large case alternators during the late 90's. I believe it was during the 7.3 years. You would definitely want to do a big 3 upgrade with that as well.

Okay there's also these guys who state:

These are 100% NEW Alternators with No Core Charge, you keep your old unit. Built in the USA from parts from around the globe, we try to use as many north american made parts as possible. The Ford Motorcraft Type 6G Series Standard 110 Amp SMALL CASE 6G Alternator was first used in 1999 on the Power Stroke Diesel. in our opinion this Small Case Alternator was way undersized for this application, we offer the large case unit that fits directly in place of the small case unit, the large case alternator was offered on ford vehicles prior to 1999.

160, 200, and 250 Amp Ford Motorcraft Type 6G Series High Amp Alternators

With Heavy Duty Single, Dual or Triple Duty Bridge Rectifier with Heavy Duty Voltage Regulator

USA Built, Ford Motorcraft type 6G series 200 high amp, large case Alternator with Heavy Duty Voltage Regulator and Heavy Duty Single, Dual or Triple Bridge Rectifier . This unit is built in the USA with NTN bearings which are the OE Bearings used by Ford, Heavy Duty Bridge Rectifier inside the Alternator with COPPER Diodes and Aluminum Heat sink rated at 210 amps, Stators from Georgia, Heavy Duty Voltage Regulators and all Top Quality Components. Single Rectifier units do not have the extra Rectifier box as shown in the picture. Singe Rectifier Alternators install just like normal without the extra process of installing the remote Bridge Rectifier box.

The 250 amp Ford Motorcraft type 6G series high amp alternator requires a Quicktifier Remote Bridge Rectifier because the output is to great for a single bridge rectifier. Please make a Quicktifier selection when ordering your high amp 6G series alternator. If you order a 6G series alternator at over 200 amps without a second set of diodes, it will fail more quickly , 6G series bridge rectifiers are not heavy duty enough to handle the excessive amperage alone .

Whenever possible it is best to upgrade from the Small Case 6G series Alternator to the Large Case unit. The Large Case Alternator gives you more power at idle, absorbs and dissipates heat better and will last longer at higher amperages. The Large Case Units bolt directly in place of the small case and the plug is the same. F Series, E Series, Excursions, Explorer and Expeditions and Mercury Mountaineer with the power Stroke Diesel Motor Many Ford trucks came standard with the Small Case alternator and can be upgraded to the Large Case unit or better performance.



Check them out...

 

Ignoring the capability of the alternator, I think your project is a stretch.

120 amps at 12 volts (I use a pessimistic number) over 50' (round trip) would have a 4% voltage drop with 2/0 cable, 2.5% drop with 4/0 cable. That's the good news.

The bad news is that a 120 amp DC-DC charge is going to pull more than 120 amps from the source. Check the specs on the charger you're looking at. I'm guessing it could be as much as 150 amps. That puts you at a 3.14% voltage drop with 4/0 cable, which is not optimal. Further bad news is that 50' is probably not long enough.

My Coleman Mach 15 rooftop air conditioner is rated at 19 amps as I recall. 19 amps x 120 volts = 2280 watts. Through an inverter, 2280 watts / 12 / .85 (inverter inefficiency) = 223 amps.

Consider putting solar on the roof instead.

 

My roof AC pulls about 1100 watts continuously (more peak when starting, of course).

I'm considering roof solar too which would add capacity when driving during the day, but I want to have enough capacity to be able to drive at night with the AC running. I'm going to do the Victron setup, which will combine all the sources and "balance" them to some degree.

The "easy" way to do this is to put an additional (big) inverter in the truck and go back using 120V, save me on wire, but I'm not too keen on having to buy another big inverter/transfer switch/etc to support this use case. The nice thing is that by staying in DC, all the DC charging sources combine automatically. I could do PowerAssist on the Victron to limit the draw to 15A, but I'd have to do that manually each time.

 

This is more info on Ford alternators.


https://alternatorparts.com/ford-che...ternators.html

Ford Type 1G and 2G Series Alternators

Ford's 1G series alternator was a lot like the Delco 10DN, externally regulated and not very powerful. Ford added internal regulation with the 2G series alteranator. But the 2G series alternator has a power plug, which cannot handle high power. The 2G power plug can become a fire hazard at over 150 amps. We recommend replacing the 1G and 2G series with the 3G series heavy duty alternator. An internal, self-exciting voltage regulator, and our new Ford type 3G all-in-one wiring harness ( Part #925606 ), make installing the 3G simple.


Ford Type 3G, 4G, and 6G Series Alternators



After a high failure rate with the 2G and 1G series alternators, the 3G series alternator has been continuously used on Ford trucks for many years. We offer top quality, large case 3G series alternators. Ford's 7.3L Power Stroke diesel F-series uses the 3G exclusively until 1999, when it was replaced with the 6G series. This small case 110 amp alternator was used on the majority of Ford trucks from 1999 till present. The 4G alternator is very popular on Ford vehicles with the dual alternator option. For the most part, we recommend replacing the small case 3G and 6G series alternators with the large case versions. Take a look at this page to identify large case units from small case: How can I tell if my Ford alternator is large case or a small case?

The 4G series alternator was not commonly used. It was, however, popular on the diesel engine with dual alternator option. It also existed for a while on the Lightning Series F-Series trucks. We recommend replacing the 4G with another 4G, which we upgrade using the Quicktifier Dual or Triple Rectifier Kit. Adding diodes to the bridge rectifier circuit help balance the load, decreasing heat and thermal cutoff.

 

https://www.onallcylinders.com/2015/...ut-alternator/

 

this elaborate system only uses a 30 amp dc to dc charger.

 

Good article. Thanks for posting fritz.

 

I had a 240 amp mechman alternator on my old 7.3, other than my glowplugs hatting it (crappy 11v beru plugs) it ran very well. If running an alternator with that much juice, doing the "big three" cable upgrade would probably be a good idea. At the load your looking to support you are heading into MCM sized cable territory, solar might be a better option.

Also with a King ranch, are you sure you don't have dual alternators from the factory on that truck?

 

Absolutely on upgrading the big three wiring when going to a higher output alternator.

https://learn.sonicelectronix.com/how-to-big-3-upgrade/