Possible uses for APU on bus

richard5933 · May 04, 2019, 06:27:12 AM

Anyone thought about possible uses for a truck APU on a bus? The new units by Thermo King provide 13,800 BTU of a/c & heat and up to 120 amps of 12v power. They can also be set up to pre-heat the bus engine.

I know that there would be some redundancy if a bus already has a 120v a/c setup and a generator, but I was looking through some truck sites recently and it seemed like this type of setup could have some bus applications.

lostagain · May 04, 2019, 07:00:57 AM

I've never driven a truck with an APU. I've always had a Webasto type diesel heater, which are great. But I have spent many nights in truck stops with APUs next to me. The SOBs are noisy! I'd rather have an idling truck beside me than an APU. And they come on and off every 20 minutes or so. I don't see why you would want one if you already have a generator and a heater and AC.

JC

DoubleEagle · May 04, 2019, 07:06:56 AM

They might have some value if the price was right, but they are sized for a truck cab/sleeper and would only be enough for part of the bus unless it was well insulated. The ones I have had on trucks had a good amount of vibration and noise, and were equipped with Chinese parts. They can be annoying because they cycle on and off like the reefer units, which are the worst trucks to try to sleep near.

luvrbus · May 04, 2019, 07:08:21 AM

The APU I been around it would make no sense to have one in a bus like JC posted those 3600 rpm 2 bangers make a lot of noise

buswarrior · May 04, 2019, 07:18:30 AM

The truck oriented machinery is typically sized too small and priced too high/ cost - benefit out of whack for busnut use.

Good used take-outs are rare, every other trucker is on the look-out for 'em, and they are commercially motivated...

Beware the marketers, that "120 amp" advertisement is just a standard automotive alternator, and will rapidly fail, same as the rest of those alternators, if called on to do anything more taxing than maintain a start battery and run normal automotive loads. The other guy was advertising a 60 amp alternator, so you know what motivated this...

However, if one became available at the right price, that doesn't mean a suitable power system couldn't be designed around one. It has an engine and pulleys... imagination is all that's needed beyond that.

I'd use one of those engines to drive a big air cooled bus alternator, controlled with a Balmar multi-stage regulator and make a DC generator.

different strokes for different folks

happy coaching!
buswarrior

buswarrior · May 04, 2019, 07:20:46 AM

The Balmar would allow me to program the alternator back, if it proved to be too much load for the little screamer.

Fancy stuff, the boating peeps are more likely to use.

happy coaching!
buswarrior

luvrbus · May 04, 2019, 07:40:07 AM

Trucker want those because of the idle laws imposed on trucks I bet one of newer trucks would idle cleaner than the little engine screaming all night on the APU

DoubleEagle · May 04, 2019, 07:51:39 AM

The catch is the truck computer won't let that clean engine idle for longer than what the trucking company sets it at. The newest truck I had was equipped with extra batteries that powered AC/Heating for overnight sleeping, but it did not cut it when it was hot and humid. I turned the truck in and quit. Trucking is not as much fun as it used to be (if it ever was). The previous APU's were like having a unevenly loaded washer on spin cycle strapped to the floor.

luvrbus · May 04, 2019, 08:12:04 AM

Quote from: DoubleEagle on May 04, 2019, 07:51:39 AM
The catch is the truck computer won't let that clean engine idle for longer than what the trucking company sets it at. The newest truck I had was equipped with extra batteries that powered AC/Heating for overnight sleeping, but it did not cut it when it was hot and humid. I turned the truck in and quit. Trucking is not as much fun as it used to be (if it ever was). The previous APU's were like having a unevenly loaded washer on spin cycle strapped to the floor.

Yea I disabled Ronnie's on a truck he bought to pull a dump trailer with it was set at 5 minutes

Boomer · May 04, 2019, 09:02:11 AM

Always wondered why ThermoKing didn't set up reefers for supplying truck power, the unit is running anyway. Would be easy to do.

DoubleEagle · May 04, 2019, 09:12:09 AM

They don't run continually, only on demand for cooling, so they would not supply steady power.

chessie4905 · May 04, 2019, 05:06:00 PM

Why would you screw around with an apu in a coach conversion? If you want to run something when no ac current or inverter is available, why not just get a small Honda gas unit that will run your ac or heater, and maybe a little extra. They are very quiet and economical. One ac should be enough at night anyway.

richard5933 · May 04, 2019, 05:38:22 PM

Some good points made. I have never used an APU before, so my question was more about the potential. Seemed like the concept could augment a bus's other systems, but after reading the comments maybe not.