dual alternators

[stevenal]

I see Superduties have dual alternators listed as an option. Anyone have this setup? Do you like it? And how are the loads separated? Thanks.

[woodhog]

BigToe wrote:
Dual alternators also serve another purpose in diesel engines: to protect the glow plugs from early burn out.

As diesel engines came aboard light trucks in the late 80's and early 90's, some ambulance package vehicles were fitted with 215 amp alternators in Fords. But by the late 90's, Ford abruptly stopped installing single high amp alternators, and instead installed two alternators.

The reason? Saving the glow plugs, due to steadily increasing emissions regulations that required the glow plugs to continue to burn for a couple of minutes AFTER the engine was already started. This afterburn time with the engine running created a new problem. High amp alternators could more than meet the electrical load demand, recharging the batteries after startup with as much current as the batteries could absorb, while maintaining full regulation set point voltage. This was a problem for glow plugs, especially earlier on trucks that do not have sophisticated PCM controlled alternators.

The heating element of the glow plug has a fixed resistance that does not change, even if the glow plug gets hotter and hotter. If resistance is fixed, then an increase in voltage will automatically cause an increase in current.

Believe it or not, most glow plugs are rated at around 11 volts. Some as little as 10.5v, and some are 11.5v. Glow plugs are designed to work at lower voltages, because their PRINCIPAL purpose is to do their job PRIOR to the engine starting, relaying solely on battery power alone.

If you hooked up a volt meter to your electrical system and turned the key on, but not starting the engine, on a cold morning, you might see only 10.5 volts, even if your batteries were new or freshly charged to 13v. The drop in voltage is due to the glow plugs operating prior to start. The current draw reduces the voltage, hence glow plugs are designed the operate at the voltage they will typically see, which is a volt or two less than 12v nominal.

But now start the engine... and the alternator kicks on, increasing system voltage toward the regulator set point, which might be 14.2v. With cold start emissions reduction mandates, the glow plugs do not shut off, but continue to burn for up to 2 or even 3 minutes in the latest models. Yet with the engine running, there is now 14 volts available to them, which increases the current the glow plugs will see, in the absence of any other intervening regulating device.

Fortunately, modern day glow plugs DO have a self regulating device in the form of a secondary pass thru resistor that IS temperature sensitive, and in fact has a very high thermal coefficient. As this pass thru resistor gets hotter, it's resistance increases, and the increase in resistance reduced the current flow, which counteracts the increase in voltage which would otherwise increase it.

Let's at this point establish that when glow plugs consume too much current, the tips can swell, making them impossible to remove without removing a head, and even worse, the tips can break off inside the cylinder, ruining a motor. We don't want glow plugs consuming any more current than necessary to get the engine started and meet cold start emissions.

Getting back to the dual lower power alternators, versus a single high power alternator, the single high power alternator that easily meets all the current demand of charging the potteries and continuing to power the glow plugs, even at idle, will maintain a higher system voltage. On the other hand, an underpowered alternator, that is anemic at idle, perhaps only capable of generating 50 amps at idle... cannot keep up with recharging the batteries and continuing to supply the glow plugs the current that the glow plugs can consume before the secondary pass through resistor that self regulates the glow plug gets hot enough to increase resistance and reduce current demand.

So this was how Ford started protecting the glow plugs in diesel engines... by fitting two alternators instead of one, and keeping the second alternator turned OFF during engine start, as well as anytime the PCM commanded the glow plugs to be on. Ford also issued letters to ambulance builders threatening to pull their Qualified Vehicle Modifier approval status if they tried to go back to their old ways of installing a single high amp alternator, or leaving the dual alternator set up but replacing the primary alternator with a higher amperage model.

Once the glow plugs turned off (depending on Engine Oil temperature, barometric pressure, a total on time limitation timer, and system voltage), the PCM went ahead an let the second alternator kick on and come on board supplying more electrical power to the system.

Of course, over the 19 years since Ford moved to dual alternators to save glow plugs, Ford has since moved to PCM controlled alternators, and three stage glow plugs with more reactive self regulation. But 20 years ago, saving the glow plugs (or rather, saving warranty engine replacements due to glow plug failure) played a significant part in the decision to go with two smaller alternators, and keeping one turned off during glow plug operation, in order to limit the electrically generated power available to the glow plugs as part of the regulation strategy.

Thanks for one of best explanations of something I have ever seen on the TC board..

[K_Mac]

Had/have two of em' also on all my trucks. If you order plow pkg. it's standard, along with the front stabilizer bar, even though my plowin days are over

[Hodag1]

On the Ford 6.7 diesel they work in parallel and cannot be easily separated. Aparently the computer is hunting for both of them.

[Kayteg1]

I am highly mechanically-inclined and even I have degree in different majors -cars have been always my hobby and I am die-hard DIY in vehicle repairs.
Still when I open the hood of my new SuperDuty, I found heat exchanger that I could not identify. Later found on the net it is liquid-cooled intercooler.
In old days I would investigate such design, but now I rather enjoy my early retirement.
Truck has long warranties and MAYBE I will change oil on it, but don't plan to learn every switch under the hood.

[Bedlam]

Are you trying to say that people will not keep up with technology even if they are technology oriented themselves? I will agree with that statement if the person thinks they can learn once and not continue learning. In my job, it is constant education built on top of a large foundation of basics. The foundation doesn't really change with new technology, but the terminology is in constant churn even if the principle hasn't changed.

[Kayteg1]

Let me rephrase it for you.
Technology change with the speed that even inclined people will loose the connection sooner or later.

[trail-explorer]

Kayteg1 wrote:
Technology change the way that even inclined people will loose the connection sooner or later.

This phrase makes no sense at all.

[Kayteg1]

Technology change the way that even inclined people will loose the connection sooner or later.
My 2007 Powerstroke had long-glowing plugs.
Even in California I had to sit few seconds before I could turn the engine over.
Than the computer would not activate alternator for a few minutes, probably to avoid plugs over-voltage.
But in times when I had to move the truck on the yard couple of times, it would not turn on the 3rd as the batteries never had recharge.
NO WAITING TIME FOR GLOWING ON MY 2017 POWERSTROKE
that things fires on instant on cold 50F mornings.
out of curiosity I need to hook up voltmeter to it.
Bad news, it sounds like gasoline Chevy 4-banger, but than it takes some serious reeving to hear it.
Don't ask me for pictures of dual alternators. I took a peak and you hardly see alternators buried behind water-cooled intercooler and other stuff.
Next time I plan to open the hood will be about 10,000 miles.

[towpro]

Wow, sure glad my diesel don't have glow plugs 🙂

[BigToe]

Dual alternators also serve another purpose in diesel engines: to protect the glow plugs from early burn out.

As diesel engines came aboard light trucks in the late 80's and early 90's, some ambulance package vehicles were fitted with 215 amp alternators in Fords. But by the late 90's, Ford abruptly stopped installing single high amp alternators, and instead installed two alternators.

The reason? Saving the glow plugs, due to steadily increasing emissions regulations that required the glow plugs to continue to burn for a couple of minutes AFTER the engine was already started. This afterburn time with the engine running created a new problem. High amp alternators could more than meet the electrical load demand, recharging the batteries after startup with as much current as the batteries could absorb, while maintaining full regulation set point voltage. This was a problem for glow plugs, especially earlier on trucks that do not have sophisticated PCM controlled alternators.

The heating element of the glow plug has a fixed resistance that does not change, even if the glow plug gets hotter and hotter. If resistance is fixed, then an increase in voltage will automatically cause an increase in current.

Believe it or not, most glow plugs are rated at around 11 volts. Some as little as 10.5v, and some are 11.5v. Glow plugs are designed to work at lower voltages, because their PRINCIPAL purpose is to do their job PRIOR to the engine starting, relaying solely on battery power alone.

If you hooked up a volt meter to your electrical system and turned the key on, but not starting the engine, on a cold morning, you might see only 10.5 volts, even if your batteries were new or freshly charged to 13v. The drop in voltage is due to the glow plugs operating prior to start. The current draw reduces the voltage, hence glow plugs are designed the operate at the voltage they will typically see, which is a volt or two less than 12v nominal.

But now start the engine... and the alternator kicks on, increasing system voltage toward the regulator set point, which might be 14.2v. With cold start emissions reduction mandates, the glow plugs do not shut off, but continue to burn for up to 2 or even 3 minutes in the latest models. Yet with the engine running, there is now 14 volts available to them, which increases the current the glow plugs will see, in the absence of any other intervening regulating device.

Fortunately, modern day glow plugs DO have a self regulating device in the form of a secondary pass thru resistor that IS temperature sensitive, and in fact has a very high thermal coefficient. As this pass thru resistor gets hotter, it's resistance increases, and the increase in resistance reduced the current flow, which counteracts the increase in voltage which would otherwise increase it.

Let's at this point establish that when glow plugs consume too much current, the tips can swell, making them impossible to remove without removing a head, and even worse, the tips can break off inside the cylinder, ruining a motor. We don't want glow plugs consuming any more current than necessary to get the engine started and meet cold start emissions.

Getting back to the dual lower power alternators, versus a single high power alternator, the single high power alternator that easily meets all the current demand of charging the potteries and continuing to power the glow plugs, even at idle, will maintain a higher system voltage. On the other hand, an underpowered alternator, that is anemic at idle, perhaps only capable of generating 50 amps at idle... cannot keep up with recharging the batteries and continuing to supply the glow plugs the current that the glow plugs can consume before the secondary pass through resistor that self regulates the glow plug gets hot enough to increase resistance and reduce current demand.

So this was how Ford started protecting the glow plugs in diesel engines... by fitting two alternators instead of one, and keeping the second alternator turned OFF during engine start, as well as anytime the PCM commanded the glow plugs to be on. Ford also issued letters to ambulance builders threatening to pull their Qualified Vehicle Modifier approval status if they tried to go back to their old ways of installing a single high amp alternator, or leaving the dual alternator set up but replacing the primary alternator with a higher amperage model.

Once the glow plugs turned off (depending on Engine Oil temperature, barometric pressure, a total on time limitation timer, and system voltage), the PCM went ahead an let the second alternator kick on and come on board supplying more electrical power to the system.

Of course, over the 19 years since Ford moved to dual alternators to save glow plugs, Ford has since moved to PCM controlled alternators, and three stage glow plugs with more reactive self regulation. But 20 years ago, saving the glow plugs (or rather, saving warranty engine replacements due to glow plug failure) played a significant part in the decision to go with two smaller alternators, and keeping one turned off during glow plug operation, in order to limit the electrically generated power available to the glow plugs as part of the regulation strategy.

[trail-explorer]

time for some photos.

[travelnutz]

trail-explorer,

Sorry, hadn't check back on this thread.

Answer in detail as to wiring etc:

My wires (+ and -) are #2 gauge fine strand welder cable. They go from the Duramax dual alternator junction connection to a 80 amp slide switch first and then to an 80 amp starter solenoid which is activated by the truck's key ignition system with a wire to the fuse box and then the alternator current goes thru an 80 amp marine HD fuse before going into the same gauge plastic sheathed cables going along the truck frame and up into the rear bed to another 80 amp marine fuse and the junction connection stainless wingnuts on well insulated 5/16" brass studs. Several HD wire ties hold the cables tight to the truck's frame.

Also have a lighted toggle switch mounted on the bottom of the left side of the IP so I can turn the alternative alternator current system on or off with the starter solenoid when driving if desired.

In the truck bed under the side rail at the top is where the wingnut connections (separated approx. 6" on individual thick nylon about 1-1/2" wide X 2-1/2" long and about 1" thick insulating blocks) and are located so they are up out of the way and very unlikely to be shorted out by something but still easy to reach.

From there, the same size copper cables go to 2 group 31 12V deep cycle batteries below in the space between the wheel well and the front of the bed. Easily clear even the Lance TC when we load it on including the plywood cover I made to cover and conceal the batteries and keep weather off them. Always use both + and - cables for high amps! Fine strand copper because it bends freely repeatedly without fatigue or breaking.

2 wire cables connected to the TC battery thru a sealed hole into the TC battery compartment is easily connected to the 2 brass studs so there are 3 equal batteries to power the 11-1/2' TC and its 1500 watt inverter.

When the 5h wheel is used, I connect the same size cables from the 5th wheel batteries thru an HD marine 250 amp rotary barrel switch to the brass studs in the truck bed. 5 more of the same batteries are in the front compartments of the 5th wheel and plus the 2 in the bed gives 7 larger 225 minute draw at 23 amps capacity and all recharged by the trucks alternators or the converter or even the Honda gen on the back of the 5th wheel if or when needed or desired.

In the 5th wheel, I have a mounted 2500 watt inverter with a remote control to operate inside the 5th wheel. The inverter is on a totally separate 15 amp AC wiring circuit for the inverter use with 6 mounted duplex outlets in around the inside and one outside in the fridge rear access door. One duplex has a neon indicator bulb I added to the cover near the bottom area of the fridge so it's plain to see if the inverter is on or off.

Created this system back in the 1990's on one rig and then moved it to our new ordered Duramax and it works fabulous still over 20 years since first made. Electric power both AC and DC is silent and therefore NO noise when making coffee or running the microwave or the toaster etc. 7 batteries at 225 min each having a 23 amp draw = 1575 minutes capability and can recharge so quick and easy 3 different ways! Turn any of the system on or off at several locations and all is fused too.

Fridge quits running on gas or out of gas? No problem, just mover the AC plug over to the inverter outlet 4" away. Always have plenty of AC when not on shore power or running a generator for days if desired at a time.

So easy to make the system and not very expensive and your labor is free. You do have to get off the couch and put the remote down though!

What's not to like?

[Kayteg1]

I know it is not fair comparison, but driving Mercedes I naturally compare.
Mercedes makes automatic HVAC for at least 35 years and they do good job.
For last 20 years you have dual or quad zones, so passengers can make individual adjustment.
The only uncomfortable moment is when on heat the system will still blow very hot air with cabin already warm.
There is no program that would gradually lower the heat output on our cars, but the moment last just few seconds and I learn to live with it.
Bottom line, I have my thermostat set and usually never touch it.
Sometimes when I get into the car after some workout, I lower it couple degree, but that is all.
Going to pick up my new F350 in 1 hr and then I am taking my family to Texas Roadhouse (in California) for lunch.
It is going to be exiting day.

[bfast54]

Kayteg1 wrote:

ggardne2 wrote:
Electric cabin heater is standard on new Super Duty Diesel's in cold climates. It is simply a supplemental heater to help with cabin warm-up in cold climate since Diesel engines have such a long warm-up time when the vehicle is operated at light load.

In terms of two batteries, that is to provide enough current to crank the Diesel engine in cold climates while at the same time maintaining current for your glow plug system.

Diesels do produce very little heat at idle to start with.
Cold-climate vehicles do come with Webasto heaters as on average commute in cold weather diesel never reaches operating temp.
For some reason Webasto is not an option on US models.
Years ago I ended up in No. Dakota in winter with intention to sleep in the cabin.
The cabin was well warmed up due to hauling, but right after midnight I woke up due to cold. The hot engine at idle cooled down and dash temp gauge went down to 0.
I pushed gas pedal to give it more heat, but it was not much use.
Electric heater not only keeps cabin at comfort level, but also adds load to the engine- keeping it warmer as well.
But dual alternators are installed without electric heaters as well.
Might be good for those who install 4000W stereo in their Superduties.

Hmmmmmmm...I am confused ........You appear to be talking about DIESEL.....

yet you........"Pushed GAS PEDAL".........???????????......:h

My F-350 diesel Dually has 2 alternators....Faster recovery of the Dual Batteries.

Dual Batteries are needed for Starting.....Diesel uses COMPRESSION IGNITION.....VS........Spark Ignition for Gassers.