Generator or APU?
- Thread starter LoRoad
- Start date
pugslyyy
Expedition Vehicle Engineer Guy
All depends on what you are trying to do. A truck APU is a diesel generator with extra "stuff" - if you were to use it as your sole source for house AC/heat and also wanted to keep your engine block warm when parked in cold weather it could be a nice integrated package.
LoRoad
Adventurer
That is correct.
I am trying to determine which is better for the multipurpose use of engine heater, cab heater, camper heater, & AC, as well as charing of house batteries. Additionally if run through an inverter could it be used for direct power as well. A generator can do these things, albeit in a different fashion, also. I'm trying to understand if one vs the other might be a better choice for this:
http://www.expeditionportal.com/forum/threads/116121-I-ve-been-doing-a-little-design-work
The APU we are looking at can have two high capacity alternators, each set up so that if one goes down the other can continue limping along; thereby having redundancy. If a generator goes down, you need another gennie for redundancy.
java
Expedition Leader
One thing I found with my generator, It can charge the batteries very quickly over using an alternator. Although I don't know what the charge circuit is on that APU, but my charger will push 90 amps to the batteries.
One thing to look at it what id the fuel consumption of the APU vs running a generator for a couple hours to charge batteries then power the heat and other systems from the batteries?
I do like the idea of the APU though if its quiet.
One other thing, it seems most built in generators need to be removed from the truck to do anything other than an oil change.... Don't ask how I know. It was pretty simple one mine, 8 bolts and a fuel and a couple electrical connections, but required a floor jack and some patience. I wouldnt want to do it in the field.
One thing to look at it what id the fuel consumption of the APU vs running a generator for a couple hours to charge batteries then power the heat and other systems from the batteries?
I do like the idea of the APU though if its quiet.
One other thing, it seems most built in generators need to be removed from the truck to do anything other than an oil change.... Don't ask how I know. It was pretty simple one mine, 8 bolts and a fuel and a couple electrical connections, but required a floor jack and some patience. I wouldnt want to do it in the field.
Haf-E
Expedition Leader
If you are wanting to have air-conditioning - these APUs can be a good option to consider as they provide not only the power but directly run an air-conditioner compressor. This assumes you will not be "plugging in" at campgrounds as the AC only works from the APU. This is more efficient than running an AC generator and powering a roof top AC unit - and also weighs less.
Some of these APUs did also provide heat via the engine but from what I've seen they have switched over to just running electric heat off the alternators as the plumbing is too much mess and maintenance - wiring is simpler. Again - weight is a concern on these units when used on long haul trucks which get paid for the weight they carry.
DC alternators driven by a engine like this can charge a battery well if they include a "smart" type field controller that does three stage charging. I would think that they would include this. The dual alternators is a good idea - both from redundancy and performance - two alternators will work better than one larger one and there would be less stress on the pully/belt.
Some of these APUs did also provide heat via the engine but from what I've seen they have switched over to just running electric heat off the alternators as the plumbing is too much mess and maintenance - wiring is simpler. Again - weight is a concern on these units when used on long haul trucks which get paid for the weight they carry.
DC alternators driven by a engine like this can charge a battery well if they include a "smart" type field controller that does three stage charging. I would think that they would include this. The dual alternators is a good idea - both from redundancy and performance - two alternators will work better than one larger one and there would be less stress on the pully/belt.
jbob
Observer
Those are really neat.
LoRoad
Adventurer
That's a really good point. thanks.
DirtWhiskey
Western Dirt Rat
Figured I'd chime in here. My uncle runs a fleet of 20 long haulers out of Vegas. He has tried three different APU units on his fleet and I've only heard him grumble and complain about them. They cost somewhere between 6 to 10k a pop and they all have some really serious "automatic" systems integrated into them.They are complex and hard to service in the field. They were rushed to market because of new idling laws and even the really pricey units have a checkered history. My hope is that they have improved over the years and I would think that is the case, but he still grumbles. I'll have to ask him about which brands he has experience with.
LoRoad
Adventurer
That would be really helpful. Thanks for the input and will patiently wait to here what your uncle says. I'd know about the no-idle reason, and of some 'grumbling', just wondering the same as you if they've gotten any better over the years. The price tag is steep for sure.
SoCal Tom
Explorer
I think I would go with the generator. Integrating the APU would be complex, and would have to be more likely to fail. 200amps would be about 2400 watts. A generator that size could be portable so you would have more flexibility with use or loading. Also, service would be easier, and repair shops would be easier to find. A larger generator could power all the things the APU provides, and give much more flexibility and would be easier to install.
Tom
Tom
Haf-E
Expedition Leader
The issue with using a small generator is that there are not very many available with diesel engines. So this would require another fuel tank for the gasoline and the issues involved with that.
I think the some of the servicing issues of many of the APUs are related to interconnection of them with the AC and heating systems - that seems like it would messy. There is a nice Cummins/Onan unit that is used in many of the higher end RVs called the "QD series" which are available in a small as 3200 watt with an inverter-output (so the power quality is better). The QD series includes an acoustic enclosure so its quiet - but it does weigh over 200 pounds and is about 30"L x 18"H x 18"D. They cost about $5000 - so not cheap. They say it will run a big rooftop AC unit and also could power the radiant floor heating system in the winter.
Worth considering...
I think the some of the servicing issues of many of the APUs are related to interconnection of them with the AC and heating systems - that seems like it would messy. There is a nice Cummins/Onan unit that is used in many of the higher end RVs called the "QD series" which are available in a small as 3200 watt with an inverter-output (so the power quality is better). The QD series includes an acoustic enclosure so its quiet - but it does weigh over 200 pounds and is about 30"L x 18"H x 18"D. They cost about $5000 - so not cheap. They say it will run a big rooftop AC unit and also could power the radiant floor heating system in the winter.
Worth considering...