UHG or standard Generator?

[RLSmith4602]

We are looking at 2 slightly used Promaster vans. One is the Zion with the UHG and 2-200ah lithiums, the other is a Legend with standard gen and 2-150ah lithiums. We’ll be using the unit for the usual weekenders, a week here and there and a planned 3-4 week cross country trip next year.
I’m no stranger to camper trailers and generators. I currently own 5 gens with one of them being a new Generac 2800I (suitcase style like the small Hondas).
The floor plan in both are identical with the exception being the one with the standard gen is much more refined and just looks a lot more modern and stylish. Read as…..wife like interior better! LOL
My question is and putting interior aside, if you could pick a one with a UHG or a standard gen for the described intended purpose, which would you prefer?
We will be running the ac quite a bit as we’re in the south.
Thank you everyone for your opinion and/or suggestions.

PS……I already know to keep the wife happy or it really wouldn’t matter which one I pick! I’d still be miserable! 🥴

[Rlum]

Originally Posted by RLSmith4602

We are looking at 2 slightly used Promaster vans. One is the Zion with the UHG and 2-200ah lithiums, the other is a Legend with standard gen and 2-150ah lithiums. We’ll be using the unit for the usual weekenders, a week here and there and a planned 3-4 week cross country trip next year.
I’m no stranger to camper trailers and generators. I currently own 5 gens with one of them being a new Generac 2800I (suitcase style like the small Hondas).
The floor plan in both are identical with the exception being the one with the standard gen is much more refined and just looks a lot more modern and stylish. Read as…..wife like interior better! LOL
My question is and putting interior aside, if you could pick a one with a UHG or a standard gen for the described intended purpose, which would you prefer?
We will be running the ac quite a bit as we’re in the south.
Thank you everyone for your opinion and/or suggestions.

PS……I already know to keep the wife happy or it really wouldn’t matter which one I pick! I’d still be miserable! 🥴

Interesting dilemma? Both battery banks are on the small side 200-300ah. So not much running on batteries. Running your AC will be from your car or generator. Lots more gas running from auto motor. I have read the Promaster does not like to be idling for long periods of time. Personally, I would prefer to use a dedicated generator to run the AC. Unfortunately, some places do not allow running either the auto engine or a generator past 9:00pm?

[RLSmith4602]

Originally Posted by Rlum

Interesting dilemma? Both battery banks are on the small side 200-300ah. So not much running on batteries. Running your AC will be from your car or generator. Lots more gas running from auto motor. I have read the Promaster does not like to be idling for long periods of time. Personally, I would prefer to use a dedicated generator to run the AC. Unfortunately, some places do not allow running either the auto engine or a generator past 9:00pm?

I’m assuming the places with quiet hours would be campgrounds with most having hookups? Which in that scenario I’d use shore power.
I guess I’m just mainly trying to decide which would be better for our style and climate. I love the idea of a UHG but I’m thinking it wouldn’t serve us well in hotter climate running the ac.

[Rlum]

Originally Posted by RLSmith4602

I’m assuming the places with quiet hours would be campgrounds with most having hookups? Which in that scenario I’d use shore power.
I guess I’m just mainly trying to decide which would be better for our style and climate. I love the idea of a UHG but I’m thinking it wouldn’t serve us well in hotter climate running the ac.

UHG is great if you want to run the ac while driving. Good for pets/kids in the back. But a generator can also be run in the back to power the generator if you want. I have the Onan 2800i quiet generator. I can run it to power the AC if necessary. Although I generally will run it to charge the battery bank and exercise the genny. UHG is great if you are driving a lot.

[RLSmith4602]

Originally Posted by Rlum

UHG is great if you want to run the ac while driving. Good for pets/kids in the back. But a generator can also be run in the back to power the generator if you want. I have the Onan 2800i quiet generator. I can run it to power the AC if necessary. Although I generally will run it to charge the battery bank and exercise the genny. UHG is great if you are driving a lot.

Would I be correct in assuming the Onan would be better for ac use at night if boondocking where no quiet hours are in affect?

[tarp]

If you want to use the rv for summer rest/roadside stops for lunch, nap you need something powerful to run the ac. That said, you probably wouldn't do that a whole lot.

[Urlauber]

Originally Posted by RLSmith4602

Would I be correct in assuming the Onan would be better for ac use at night if boondocking where no quiet hours are in affect?

There are pro's and con's, and you just have to decide which fit you better.

Noise-wise, I would think the UHG has the edge. Also, maybe it takes up a little less space.

On the other hand, the generator is probably a bit more efficient in running the AC than idling the engine. We did some calcs before and the generator came out ahead.

Also, running the engine creates more heat than running the generator. I think.

Some cars should not idle excessively, I believe the diesel Sprinters are among them, while the gas engines tend to care less.

I'd say with a larger battery bank and more driving (in general) the UHG may be better. With a smaller battery bank and more boondocking the genny may win out.

Me, I went with a small battery which has no chance of running the A/C, and a genny that does. I rarely run the A/C, but sometimes it is absolutely needed.

[Rlum]

Originally Posted by RLSmith4602

Would I be correct in assuming the Onan would be better for ac use at night if boondocking where no quiet hours are in affect?

The Onan 2800i is pretty quiet. Probably less noisy than most AC units

[avanti]

Originally Posted by Rlum

Lots more gas running from auto motor.

Not sure that is true. There are lots of variables, but all the numbers I have read suggest that consumption is pretty similar for an Onan vs idling. People usually report <.5 gal/hour for both.

[booster]

Originally Posted by avanti

Not sure that is true. There are lots of variables, but all the numbers I have read suggest that consumption is pretty similar for an Onan vs idling. People usually report <.5 gal/hour for both.

I have seen the same thing when I have looked for information. Might be different is you have a high idle setting.


Even at idle most of the UTGs will charge lithiums faster than the regular generator will because the generator has to go through the shore charger and you are limited to its output.

[Rlum]

Originally Posted by avanti

Not sure that is true. There are lots of variables, but all the numbers I have read suggest that consumption is pretty similar for an Onan vs idling. People usually report <.5 gal/hour for both.

I have a Promaster. The scan gauge indicates .59 to .62 gph when idling. The Onan 2800i burns about .48 gph on full power output. My AC uses 1400 watts when running on its highest setting. During the night, AC will likely cycle on and off so not running full out. Lets assume it runs at 10amps(1200 watts) continuously. That would be less than 1/2 power of .24 gph. So in my opinion, much less fuel to run AC from genny.

[booster]

Originally Posted by Rlum

I have a Promaster. The scan gauge indicates .59 to .62 gph when idling. The Onan 2800i burns about .48 gph on full power output. My AC uses 1400 watts when running on its highest setting. During the night, AC will likely cycle on and off so not running full out. Lets assume it runs at 10amps(1200 watts) continuously. That would be less than 1/2 power of .24 gph. So in my opinion, much less fuel to run AC from genny.

That sounds way high for idle consumption.


Assume you get 18mpg at 50mph, then .62 gallon per hour would get you you 31 miles. Using that much sitting still?

[Rlum]

Originally Posted by booster

That sounds way high for idle consumption.


Assume you get 18mpg at 50mph, then .62 gallon per hour would get you you 31 miles. Using that much sitting still?

Just telling the reading from my scan gauge. The 3.6 liter engine must burn more fuel than the Onan 2800i? It seems if the Onan 2800i single cyclinder is burning .48 gph at full power. The Promaster 3.6L at idle of 800rpm would be much more? I do not know if one could get 31 miles with .62 gallons. Mathematically yes but there is acceleration, etc. Assuming one was already going at 50mph and metered out .62 gallons, probably doable?

[Davydd]

You can't run Sprinter diesel UHG for more than 2 hours unless you drive 30-40 minutes inbetween the running for another 2 hours. Obviously that is not an overnight situation unless you have battery power. The run time is not because of the engine but for the emission particulate matter. As far as running, a diesel engine lasts longer than a gas engine in other aspects for your lifetime calculations. Plus, you need to rely on your engine to get you somewhere which is more critical. UHG have a belt from the engine alternator and separate electrical system so is not much burden on the engine as it isn't critical to the engine. A separate generator is another internal combustion engine that takes up more critical space in a small Class B vehicle and has way more separate maintenance issues.

My UHG produces 220ah at high idle and 270-280ah at highway speeds dedicated to the coach only. The engine alternator is for the chassis and in Sprinters provide 40ah regulated for the coach. To recharge the same amount of coach batteries, you would have to drive at the 7 hours to 1 hour. I can recharge a day's stay of battery use in 30 minutes sans the use of air conditioning. As I previously mentioned you cannot depend on solar. Battery power is way more important especially with an UHG and no UHG or generator if boondocking without air conditioning may be an eventual drain on your batteries that you can't replenish, in a day's driving especially with an extended stay.

Some companies are providing the 48v Volta high capacity battery system with an UHG that produce an equivalent 12v to power overnight air conditioning. ARV has gone a step further with their own 48v system that provides more power. I don't need it as I avoid air conditioning almost always.

With more coach battery (needs to be lithium) with UHG, you can eliminate all propane use, generator and solar. That's a lot of space, weight and maintenance taken up that is eliminated. A separate coach generator is old school and as I mentioned, you would be a pariah where you park overnight without shore power or boondocking near others if camping in a campground situation or on a residential street, driveway, or parking lot not running a generator. How many times are you boondocking in a NF, BLM land or on the beach alone? In your dreams. Seek shore power if you want to run air conditioning overnight.

I can't help people with older Class Bs that can't be adequately converted, people living in the south, people with special health needs or stay-in people not enjoying the outdoors unless they are buying a new van because most older vans are inadequate.

[Punkinhead]

We have 900 aH of lithium and a second 250a alternator so we haven't needed a generator yet, but I wonder if one solution is to buy one of the little 1500-2000W suitcase generators. They're quiet, light, and don't take up much space. It's not something I would typically carry but maybe it's something worth buying for the one or two trips a year where it would be handy. Next month I plan to spend a week boondocking near a river I want to fish. My batteries will last 4-5 days just running the fridge, lights, etc, but it will be hot and muggy so I might want to run the 12V AC for a few hours in the evenings. My AC pulls about 60 amps when the compressor is running. I haven't actually measured the compressor duty cycle but it seems to be 50% or less based on how often I hear the condenser fans running. So it would only take an hour or two per day to keep the batteries topped off and I wouldn't have to run the van's engine. And I could leave the generator home when I don't need it, which would be most of the time.

[W9TR]

2020 Thor 20AT here on 2019 Promaster chassis with Onan 2800 generator and 2 100 AH AGM batteries.

I’d go with the UHG. The Promaster engine can idle overnight to run the AC. With a UHG you can add more battery capacity over time.

We have 50,000 miles on the Promaster and 65 hours on the generator. Just don’t use it. Too noisy and smelly.

The Promaster engine is much quieter and pollutes way less.

UHG’s have a checkered service history so do your research on the specific model before you buy.

[RossWilliams]

I would get the UHG but not if you intend to run the air conditioning off it. Your batteries will handle AC for a lunch break and UHG will keep them fully charged. But if you are camping without shore power trying to run the AC off the UHG by idling the engine seems like a bad plan. You might as well use the vehicle AC.

[JonMN]

I have a 2022 with the Onan 2800i generator. If I was to choose between a second alternator and the generator, for us the second alternator and lithium might have been best.

The 2800i is REALLY quiet. The generator itself is mounted on 3 rubber mounts inside the case, and the whole assembly is hung from 4 more rubber mounts. You can barely hear it when it's running, and only if you have nothing else running inside. If the AC is on you don't notice the generator at all. Outside it's not quite as quiet. It's louder than idling the chassis engine but only until the electric fan on the engine kicks into high mode.

Personally, if I was in an area hot enough to need more A/C than the batteries could handle I would rather run a $3000 generator than idle my $17,000 engine. But I don't see us getting into this situation.

To me the main annoyance of the generator is that it is yet another gas engine to maintain, and, being under the van, it's a bit of a pain to access. Just built some ramps that make this way easier.

We have not boondocked yet, and generator use has been very minimal. It was handy when we had a long stay at a VRBO to recharge the batteries.

I anticipate changing my 330ah AGM to a 300AH lithium. But even with the AGM I can run our 12v A/C for 90 minutes--easily enough time for relaxing at a rest stop on a trip.

PS: Kudos to the marketer that came up with underhood generator as an alternative to second generator. Sounds way more impressive. I remember when we were looking at Class Bs the first time and looking under the hood for an actual generator!

[avanti]

Originally Posted by JonMN

Personally, if I was in an area hot enough to need more A/C than the batteries could handle I would rather run a $3000 generator than idle my $17,000 engine.

Not sure I see the logic here. It is an empirical question which of those alternatives is better. Just hypothetically, if running a given generator wore it out quickly, but idling the engine did no appreciable harm, it would be better to do the latter (and vice versa, of course), replacement costs notwithstanding.

The fact is that some engines tolerate idling just fine, and others don't.

[booster]

Originally Posted by avanti

Not sure I see the logic here. It is an empirical question which of those alternatives is better. Just hypothetically, if running a given generator wore it out quickly, but idling the engine did no appreciable harm, it would be better to do the latter (and vice versa, of course), replacement costs notwithstanding.

The fact is that some engines tolerate idling just fine, and others don't.

Yep, the idling is always a big question for most of us.


I watch the used vehicles on Craigslist regularly, and there are quite a few ex cop cars showing up there.


Many times they list the miles on the vehicle and the idling hours as they all seem to have idle hour meters in them, presumably for the maintenance intervals.


Some of the vehicles have 100-150K miles and many thousands of idling hours on them so the idling didn't seem to kill them off.


Of course they are all gas engines.