[Landcruiser]

Does anyone know if the Ford dual alternator option affects MPG?

 

[Jrl941]

I have the dual alternators, and I have consistently among the best mpg of anyone that I see post on the forum (148 AWD non ext. With Ecoboost, I get 17-19 mpg driving mostly highway in FL)

 

[Sams stock van]

No one has offered a head to head comparison. Rather, those that have and those that don't, agree one one thing. Yes, it effects mileage. The real answer lies somewhere between the mathematics crowd's estimate of insignificant to the dramatic internet opinion that you're heading to bankruptcy.

FWIW, I average 17 mpg with dual alternators with a mix of local and highway driving. YMMV.

 

[carringb]

The fact that there’s two alternators shouldn’t have any measurable affect. But… the total watts being produced can. Albeit still probably not significant. And obviously the dual alts doubles the peak output. But I suspect in most usage scenarios the average output probably isn’t too different unless you’re running an electric a/c.

 

[njvagabond]

If/when/how/much they reduce/eliminate the need for idle charging … 🤔

I’d suspect the gasoline use/w-hr for solar panels could be a far worse proposition (depending how drive to park ratio) than any alternator charging impact.

 

[kenryan]

The fact that there’s two alternators shouldn’t have any measurable affect.

I agree with @carringb above statement.

For whatever it is worth, with regards to actually producing electricity:

240 amps @ 12 volts = 2880 watts
2880 watts = 3.9 horsepower
Modern engines use about 0.38 pounds of fuel per horsepower per hour.

So, theoretically, that's about a quarter of a gallon of gas to make 2880 watts for one hour. Not exact, but should be close.

 

[BadWolf]

I do see an increase when i run my inverter while parked. My DC>AC(2200w)>DC i limited to pulling 1700w/130a off, the dual alternator(500a).

On my display
0.3gph Idle
0.5gph Pulling the 1700w
0.75gph ac on full blast + 1700w

If i want to cool off my van asap, i'll remote start the van on the app, and my thermostat also has a remote app.

So i'm getting ~3,300w per gallon treating my motor as a generator.

 

[pbethel]

Two identical vans drawing the same watts as they drive down the road the main difference would be belt and bearing friction. But why pay for dual alternators unless you have bigger loads on a regular basis.

 

[RQJoe]

I have the dual alternators, and I have consistently among the best mpg of anyone that I see post on the forum (148 AWD non ext. With Ecoboost, I get 17-19 mpg driving mostly highway in FL)

Is that from the display or actual calculated by miles driven and refueling gallons?

 

[OldMadBrit]

These vans are parachutes above 65MPH. MPG is primarily a function of how you drive them.

I can get ~16MPG touring the Sierras sedately or 11MPG if I get on it to pass every slow-assed Sprinter that we come up behind (they seem to travel the Sierras in herds these days).

Alternators generate parasitic load in proportion to watts generated. You are unlikely to be running both alternators at full load all the time. Even if you did, the effect of alternator load on MPG will most likely be lost in the noise.

 

[kenryan]

Slightly off topic:

@BadWolf how are you able to read gallons per hour consumption? Thanks.

 

[nmiller85]

Slightly off topic:

@BadWolf how are you able to read gallons per hour consumption? Thanks.

I just discovered this a few weeks ago. If you have the instantaneous mpg reading selected to show on the dash, it changes to gph at idle or when barely rolling along.

 

[johnfox123]

I agree with @carringb above statement.

For whatever it is worth, with regards to actually producing electricity:

240 amps @ 12 volts = 2880 watts
2880 watts = 3.9 horsepower
Modern engines use about 0.38 pounds of fuel per horsepower per hour.

So, theoretically, that's about a quarter of a gallon of gas to make 2880 watts for one hour. Not exact, but should be close.

Thanks for the numbers. Even if they are estimates, it's still something, and it's helpful to me for a thought experiment I'm attempting.

I'm designing my electrical system now and planning to have 3 Victron Orion 12/24-15's with a 10kwh battery bank (two 24v 200a batteries). I've been thinking I'd install a switch on the dash where I could enable or disable the Orions. The idea being that if my batteries are low when I start a long drive, but I know I'll be plugging into shore power that night, then I could disable the alternator charging to improve my MPG.

So say I'm about to drive all day and I'm at 50% house battery capacity. That means I'd need 5kwh to fully charge. Which would take about 5 hours of driving. According to your numbers above, with the Orions on, I'd need an extra 1/2 gallon of gas to charge 5kwh.

In terms of MPG, if the Orions are off, and say I'm getting 15 MPG, going 60 MPH, for 5 hrs, I'd be using 20 gallons. With them on, I'd use 20.5 gallons, which would decrease my MPG to 14.6.

So I'd save 0.4 MPG, or 1/2 gallon, or ~$2. Hmm, not as big a savings as I might have hoped for. Bummer...

Although... I think I'll add the feature anyway, just because I like to have switches and knobs to mess with!

Curious if anyone sees a hole in my math or assumptions. Note that I did see a few references online that stated "A 5-kilowatt gas generator burns roughly 0.75 gallons of fuel per hour". Gas generators probably have a very different efficiency than an EcoBoost turning an alternator, but it is interesting that the 3/4 gallon number is very close to the 1/2 gallon number that @kenryan's estimates give.

 

[gregoryx]

...
So I'd save 0.4 MPG, or 1/2 gallon, or ~$2. Hmm, not as big a savings as I might have hoped for. Bummer...
...

Certain amount of irony in any of us seeking a 1/2-gallon savings while driving four-ton rolling houses... 😏

WRT your on/off idea and considering the possible variable output / charging from alternator: you've probably already looked at the DC-AC-DC setup; but if you haven't looked at it yet, it allows you to enable/disable charging from the alternator and set it anywhere from ~75A (alternator) draw up to the limit of your Multiplus you've got planned.

You can do this control from the Cerbo touch-screen or your phone or a computer. If you have internet access in the van (and why wouldn't you with that level of spending for the electrical system), it all works remotely as well. You can also apply programming logic to the charging (based on whatever you want) for when things turn on/off/up/down.

I didn't want to dig into that on the water-heater thread, but maybe re-post your big Victron drawing in a separate thread for discussion. If you have a Cerbo GX but are planning to also implement push-button switches, that's a bit of a shame when you've got such a powerful tool available. Same with running two DC-DC units to overcome Victron's lack of a high-powered solution: just run a single inverter for about the same price as one Orion and get the flexibility to charge as high as your planned Multiplus (which will max at 70A @ 24VDC or ~1.8kW rate) /while/ using excess energy to power the rest of the system while charging the batteries.

FTR, I target sub-100% SOC by enabling/disabling charging as you suggest. I could do it programmatically (easy enough with NodeRED built in to the system); but I just tap the "button" on my mobile phone to change rate or turn off OR shut off the alternator-attached inverter itself. I do that for battery life, not for fuel savings.

 

[brío]

FTR, I target sub-100% SOC by enabling/disabling charging as you suggest. I could do it programmatically (easy enough with NodeRED built in to the system); but I just tap the "button" on my mobile phone to change rate or turn off OR shut off the alternator-attached inverter itself. I do that for battery life, not for fuel savings.

I am going to use two of my "upfitter switches" for these functions. One to turn the charger off/on, and the other to switch between "100%" and "60%" charge targets.

 

[njvagabond]

Certain amount of irony in any of us seeking a 1/2-gallon savings while driving four-ton rolling houses... 😏

Certain amount of irony in any of us seeking a 1/2-gallon savings while driving $$$ four-ton rolling houses... 😏
There I fixed it for ya.

 

[TheGoodLife]

Our 2022 Tall, extended, dual wheels and dual alternator’s is getting 14mpg in the city. Seems a little low but my Ram 1500 Hemi only gets 16mpg in the city. I wish the mpg was better on the Transit but considering all factors it’s acceptable. You can’t have it all.

 

[johnfox123]

WRT your on/off idea and considering the possible variable output / charging from alternator: you've probably already looked at the DC-AC-DC setup; but if you haven't looked at it yet, it allows you to enable/disable charging from the alternator and set it anywhere from ~75A (alternator) draw up to the limit of your Multiplus you've got planned.

Agreed, although this can just as easily be done with the standard DC-DC setup. By supplying a control switch to the Orions they can be controlled either way (switch or app). Personally, I'd much rather just have a dash switch. I don't want to be messing with my phone while I'm driving.

I didn't want to dig into that on the water-heater thread, but maybe re-post your big Victron drawing in a separate thread for discussion. If you have a Cerbo GX but are planning to also implement push-button switches, that's a bit of a shame when you've got such a powerful tool available.

Same as above, the switches don't disallow the use of the Cerbo or App, it's just one more method of control. My main goal is to achieve the same functionality as the big Blue Sea switches, but in a smaller form factor and in a much more flexible location (e.g. my main control panel, or dash, or both). My garage area might not always be easily accessible.

Same with running two DC-DC units to overcome Victron's lack of a high-powered solution: just run a single inverter for about the same price as one Orion and get the flexibility to charge as high as your planned MultiPlus (which will max at 70A @ 24VDC or ~1.8kW rate) /while/ using excess energy to power the rest of the system while charging the batteries.

I don't think I'll need to draw more than 100a from CCP2 to keep our batteries topped up (based on how often we typically drive, plug into shore power overnight, solar, and daily current usage).

Three Orions look like they'll take up the same space as a cheap 2000w inverter. And I'd rather stick with all Victron since I trust their quality. Definitely don't want to replace the Orions with a second Multi-plus -- that'd be a lot more space. I'm not overly worried about cost. (Not oblivious to it, but reliability, performance, size and standardization rank higher in importance to me).