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Old 04-23-2019, 01:36 PM   #43
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Quote:
Originally Posted by Idleup View Post
Jharrell thanks again for the reply - I suggest that you first "Study Up" before you begin to question the work of creditable experts in the field.

Certainly your Googled knowledge of Lithium charging and the parameters of fuel usage of a Sprinter diesel are only goofy assumptions. It puzzles me how you feel your knowledge is more advanced or accurate than companies such as; Lithionics, Volta, Xantrex, Nations Battery, Relion, Mercedes, Martin Maretta Aerospace technicians, or myself.

Regretfully, your futile attempt to compare your V-10 gas engine to a Sprinter diesel, revels your inabilities to understanding the article and the principals of lithium engine charging and from enjoying a well written factual article.

Regards - Mike
Again yet another appeal to authority. No math, no facts. You can't seem to refute the facts I present and instead just fall back to ad-hominem.

I understand very well how engines work and how generators and alternators work and the efficiency differences between gas and diesel and propane. When someone claims it takes 2 gph of diesel fuel to generate 3kw of electricity with a modern engine I don't need to work in the aerospace industry to know that is false.

Its ironic for a guy who didn't know how much fuel a diesel generator uses to tell me to "study up". Do you understand Carnot's theorem and why a Diesel cycle engine is more efficient than a propane Otto cycle engine? Because I think if you did you would immediately realize the issues in your fuel burn numbers.
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Old 04-23-2019, 01:48 PM   #44
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Originally Posted by Jlo11111 View Post
Sounds like diesels are a poor choice for class B's and smaller class C's. Better to go with a gas Promaster or Transit and skip all the problems. Add in a 6000W 2nd alternator, a big inverter and LifePo4 or EV grade batteries and your good to go. No worries about idling and fully charged after 2 hours.

Thanks for your reply - you might just be right, new generation smaller displacement gas engines are quickly approaching that of diesel applications.

There is some amazing development technology going into smaller gas engines with regard to power and torque. I heard rumors that Mercedes might delete their V6 diesel in 3 years in the US market.

Thanks Mike
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Old 04-23-2019, 01:58 PM   #45
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Sounds like diesels are a poor choice for class B's and smaller class C's. Better to go with a gas Promaster or Transit and skip all the problems.
Ideally, MB would make the Sprinter in the 170" WB with a gasoline engine. The Transit only comes with a 148" wheel base for the longest van (Class B), though the cutaways go all the way up to 178" WB, which is longer than the MB. GCWR is also light compared to the Sprinter, so towing is mostly out.

The Transit has a lot going for it. I just wish either they'd make a 24 ft van for a Class B with room like the Sprinters (plus better towing capacity and higher GCWR and GVWR than the Transits current have), or MB would make a gas engine for the Sprinter with similar power to the current diesel. With a gasoline generator to go with it, like Coachmen uses. And a larger fuel tank, while we're at it.
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Old 04-23-2019, 02:06 PM   #46
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Okay, so if someone wants to boondock in a Sprinter and they get both a propane generator and large amount of Lithium (say 600+ah), would you recommend that any of the following also run on propane?

1. Furnace
2. Hot water heater
3. Fridge
4. Cooktop

It looks like Midwest designs forgoes propane on all the above except #2. If you don't go with Propane for any of those, then too bad there isn't a small diesel generator, as it seems a waste to have a whole separate type of fuel for just one need.
Hello yes the ultimate perfect RV is one with lithium and an Onan generator. This way you can charge off the stock alternator when traveling and if your lithium batteries get low while parked, you would have the option of firing up the Genny.

Regarding cabin heat, if you have a diesel chassis, the diesel furnaces are the way to go, very economical. Also, there's nothing wrong with a propane furnace. Of course the way things are today is everyone wants an all electric coach!

I'll tell ya what I miss - its a 3-way refrigerator. They can keep their household refrigerators. I like the option of gas 110 or 12 v for my box. The whole residential refrigerator thing started when RV manufactures figured out they could stick cheap household boxes in coaches and tell owners they were better. What they are is cheaper. A 3 way refrigerator is 2-3 times more expensive.

I used to keep my little refrig on in my old Sprinter B and it would barely sip propane. Now they have 12 volt compressors which generate terrific heat in the cabinets since few are vented and they keep the house battery near dead even with a 200 watt panel.

As you mentioned - many manufactures to include Midwest delete the generator with lithium upgrades for two reasons; The battery is generally mounted where the Genny was, and/or they get to increase their profits by keeping your generator.

Regards - Mike
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Old 04-23-2019, 02:15 PM   #47
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Originally Posted by KanzKran View Post
Ideally, MB would make the Sprinter in the 170" WB with a gasoline engine. The Transit only comes with a 148" wheel base for the longest van (Class B), though the cutaways go all the way up to 178" WB, which is longer than the MB. GCWR is also light compared to the Sprinter, so towing is mostly out.

The Transit has a lot going for it. I just wish either they'd make a 24 ft van for a Class B with room like the Sprinters (plus better towing capacity and higher GCWR and GVWR than the Transits current have), or MB would make a gas engine for the Sprinter with similar power to the current diesel. With a gasoline generator to go with it, like Coachmen uses. And a larger fuel tank, while we're at it.
Hello as you mentioned small 4 cylinder engines are the wave of the future. They just need to get the torque up for these 3500 Sprinter applications. It's just a matter of time, many of these 4 cyl are now in testing!


I archived this video a few years back comparing a 4 cyl with a 7 speed to the Benz's work horse 6 cyl diesel. You can see in their results the little 4 banger lacked torque.



Regards Mike
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Old 04-23-2019, 02:26 PM   #48
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Originally Posted by Idleup View Post
Thanks for your reply - you might just be right, new generation smaller displacement gas engines are quickly approaching that of diesel applications.

There is some amazing development technology going into smaller gas engines with regard to power and torque. I heard rumors that Mercedes might delete their V6 diesel in 3 years in the US market.

Thanks Mike
MB stopped importing auto and suv diesels into the US in 2017.
There were allegations that they would not meet emissions standards when engine was not up to operating temps. Sprinter cargo vans have a smaller displacement engine and am not sure if it has to meet the same standards.
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Foretravel tag axle 40 ft. 500 hp/1550 ft/lbs ism 1455 watts on the roof. 600 a/h's lithium down below.
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Old 04-23-2019, 09:13 PM   #49
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Originally Posted by Idleup View Post
...

I'll tell ya what I miss - its a 3-way refrigerator. They can keep their household refrigerators. I like the option of gas 110 or 12 v for my box. The whole residential refrigerator thing started when RV manufactures figured out they could stick cheap household boxes in coaches and tell owners they were better. What they are is cheaper. A 3 way refrigerator is 2-3 times more expensive.

I used to keep my little refrig on in my old Sprinter B and it would barely sip propane. Now they have 12 volt compressors which generate terrific heat in the cabinets since few are vented and they keep the house battery near dead even with a 200 watt panel.

Have you actually any experience with compressor based fridges? I have had both and I'll never go back to a 3-way. The smaller Novacool only uses 2.2 amps and that's only when it runs. This simply is not correct. They do require 30 - 60 sq. in. of passive ventilation, but it does not create "terrible" heat at all. In fact, I cannot discern any heat whatsoever generated by mine.
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Old 04-23-2019, 10:28 PM   #50
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Have you actually any experience with compressor based fridges? I have had both and I'll never go back to a 3-way. The smaller Novacool only uses 2.2 amps and that's only when it runs. This simply is not correct. They do require 30 - 60 sq. in. of passive ventilation, but it does not create "terrible" heat at all. In fact, I cannot discern any heat whatsoever generated by mine.
I miss them too. I have big batteries and big solar, but like the fact I can run my fridge on propane for months if the sun does not shine. The facts are if you move 5000 btu's out of your fridge, you must move it somewhere else, normally outside your fridge.
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Old 04-24-2019, 07:57 AM   #51
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Here is what a little "Googling" can find on idle fuel consumption:

Click image for larger version

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https://www.anl.gov/sites/www/files/..._worksheet.pdf

Ironically this is a worksheet designed to convince you not to idle due to costs and yet show much less consumption for a class 8 12-15 liter semi at idle than what is being claimed here for a 3 liter sprinter. Even the class 8 bucket truck running the hydraulic PTO just barely hits the bottom range of your claim.

Whats nice they actually cite their sources which are properly research studies that are publicly available and in searchable form, here is one excerpt:

Click image for larger version

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https://www.tandfonline.com/doi/pdf/...-3289.59.3.354

This confirms my observation of my own large gas engine and that even larger diesel engines have lower idle fuel consumption, let alone one at half the displacement.

Contrast this with the claims made in this article:

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An Onan 2500 watt propane generator consumes .4 g/h at half load (1250 watts) and .6 g/h at full load (2500 watts). So you seem to be claiming that the propane generator will provide 3750 kwh of energy for 1.2 gal of propane and the Mercedes 3.0L diesel with secondary alternator will consume 4.5-6 gallons of diesel fuel to provide the same energy.

This seems at odds with all known literature and even seems to break the laws of physics. You are claiming that a carbureted propane generator is nearly 4 to 6 times as efficient as a diesel engine with alternator, while propane has only 65% the energy content per gallon of diesel.

You also claim that a secondary 12v alternator producing 150-175 amps pulls 7-8 horsepower from the engine, however 7 horsepower is 5200 watts while 150 amps at 12 volts is only 1800 watts, that would denote an alternator efficiency of only 34% while all modern automotive grade alternators are above 70%. Perhaps you actually where actually referencing a 24v alternator, which would instead be producing 3600 watts and would only require half the runtime for charging compared to the propane generator or running for the same time providing twice the energy.

Its seem pretty obvious the fuel consumption numbers are inaccurate, I hope this was not intentional because honestly the article seems to be written as a hit piece against alternator based charging systems. I hope you update the numbers so as not spread misinformation.
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Old 04-24-2019, 07:55 PM   #52
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As some commenters have pointed out, this is useful information IF you have the same, very SPECIFIC requirements as the OP.

However, the main reason for a second alternator and lithium is that regular automotive alternators are designed to charge lead acid on a constant voltage basis, not constant current. It is well documented that without managing temps in the alternator you'll fry your alternator eventually leaving you stranded. Replace the alternator or add controls and you'll be fine.

Moving up in voltage also gives you a ton of benefits- personally, I'm moving from 12 to 48v in my rig, hence the suggestion for a 24 alternator. Check the cable reduction when you change voltage.

Lithium also isn't inherently safe as the OP indicates. LiPo is the safest chemistry, but let's not conflate them all. Key to their safety is a BMS and most (if not all) of the expensive batteries actually have an onboard BMS to manage the cells. I am most impressed with Victron and I'm moving from Magnum to Victron to accommodate a Chevy Volt battery pack.

The biggest flaw in this argument is what about solar? A good solar install would satisfy most of these requirements, roof space being available. You could then top-off with an alternator or run the ac from a hand carry generator, if you want to run the ac.

Lithium is not a panacea to all our needs. You're trading capacity and weight for cost and complexity. YMMV
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Old 04-25-2019, 07:34 AM   #53
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Looks like I am not the only one questioning the accuracy of the article, it was posted over on a class B forum with many raising the same issues:

Quote:
[underhod charging] takes 3-4 times more fuel than a (sic) Onan generator [and] generates more pollution and green house gasses.
Almost certainly nonsense. A gasoline Onan consumes .4 gallons/hour, A Sprinter on high idle MIGHT be slightly more. A typical claim is .3-.7g/h. More importantly, the Sprinter has vastly-sophisticated emissions systems, whereas the Onan one-banger is spewing raw exhaust. In fairness, the author seems to have propane in mind, not gasoline. But if the above claim is accurate, I would love to see a citation.
Lithium & 2nd Alternators Verses Onan Generators - Mike Mas - Page 2 - Class B Forums

"Googling" is an amazing thing sin't it?

Advanced RV seems to state 1/2 gallon per hour on high idle for their alternator based charging system with the Mercedes chassis, it has an auto start stop system that will high idle the engine for 110 minutes, this can be repeated 5 times before driving to stay within Mercedes recommendations.
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Old 04-25-2019, 10:42 AM   #54
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Looks like I am not the only one questioning the accuracy of the article, it was posted over on a class B forum with many raising the same issues:

Lithium & 2nd Alternators Verses Onan Generators - Mike Mas - Page 2 - Class B Forums

"Googling" is an amazing thing sin't it?

Advanced RV seems to state 1/2 gallon per hour on high idle for their alternator based charging system with the Mercedes chassis, it has an auto start stop system that will high idle the engine for 110 minutes, this can be repeated 5 times before driving to stay within Mercedes recommendations.
I really appreciate the <b> Reasoned</b> skepticism in questioning the very reasonable sounding article that Mike put up. I am pleased there haven't been flames, but I, too, would like some questions answered as I am considering a class B with a LifePo battery system <I>specifically to eliminate the generator</I>.

1. I would love to see the data on the "high failure rate" of the underhood generators/second alternators. Not, as you say, just an appeal to authority. Shouldn't there be DATA available that is in an organized, readable format? If so, couldn't it be provided so we can ALL benefit from the knowledge?
2. I would like to see the Mercedes "stop Notice" to Up-fitters to dis-allow any auto-start systems from being installed on Sprinters for extended idling, as well as limiting their alternators output." If this can be cited as authoritatively as it has been, then there should be some evidence that it has been done - perhaps a copy of the "Stop Notice"? Do I dare google it (I did, no luck)?
3. The GpH data on idling a 3.0 Mercedes diesel vs a small Onan geneset should be easy to lay out - It looks like claims of a huge disparity have been questioned and could be answered with data...not just basically, "trust me, I'm an expert"...If there's data, there's a spreadsheet with comparisons and a conclusion. Let's SEE the data, not just a disparagement of "googling".

again: I'm actually trying to make a decision based on good information. Several have called BS on some of Mike's claims also using their experience/expertise and some data. In response, I'd like to see the data. I'm not an expert. I have participated in research and appreciate looking at the spreadsheets, comparisons and explanation of the methods and conditions. Something seems to be missing here, am I wrong?
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Old 04-25-2019, 01:39 PM   #55
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To point one- hereís a primer to the problem: https://shop.pkys.com/Alternator-Lithium-Battery.html

Peter is awesome. Boats have been trying to solve for this problem for longer than RVís since they donít have generators.

Hereís a thread about sprinters: https://sprinter-source.com/forum/sh...ad.php?t=57773
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Old 04-25-2019, 08:30 PM   #56
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To point one- hereís a primer to the problem: https://shop.pkys.com/Alternator-Lithium-Battery.html

Peter is awesome. Boats have been trying to solve for this problem for longer than RVís since they donít have generators.

Hereís a thread about sprinters: https://sprinter-source.com/forum/sh...ad.php?t=57773
Thanx. First bit. Helpful.
Send Bit: Gave me a headache - was 2 years old so there's been some progress, I assume, since...?
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