*As first seen in Trailer Life Magazine*
The last time we had a truck camper out on the beach, it was a chilly April weekend, and we needed to keep the heat on at night. The problem was, we had only one battery out of a possible two, and it was a small one. It worked until about 3 in the morning when the low battery made the LP-gas alarm sound, followed by our adrenaline glands slamming into high gear. We had no generator with us, so our only option was to start the truck and get the charge line to power us up, and the diesel rattled on through until morning. Fortunately, no one was around us.
The RV PHD Newsletter is a reader-supported publication. To receive new posts and support my work, consider becoming a free or paid subscriber.
For us, towable and truck camper owners, portable inverter-generators are usually the power source of choice. The power is clean and reliable, and they’re quiet for use in a camping environment. Problems arise when deciding where to carry one and its fuel.
The legacy 2500-watt Onan propane-powered generators have been around for a long time; they’re quiet and reliable. Many truck campers and Class B motorhomes come equipped from the factory or are at least prepped for one. But is it possible to improve the best horse in the stable? Cummins Onan thought they could and asked us to try it out when they were done. So, we bought an old 2005 Lance 1025 truck camper with the legacy propane 2500-watt generator to do a before and after test.
Inverter Generators
The new QG2500i LP is a whole new concept in built-in RV generators. Onan has long built quiet, high-quality RV generators. The quietness of these comes from a smooth operating engine, a well-insulated case, and a well-muffled exhaust. But the QG2500i, available in both electronic fuel injected (EFI) gasoline (QG2800i) or LP gas models, continues the tradition of quietness but adds new technology to the mix to make the power output better while making the genset smoother, quieter, and more efficient and reliable.
There are some essential differences between legacy generators and inverter-generators. Simplified, a generator’s engine uses a stator and rotor system to create alternating current (AC) that is sent to loads in the RV. With an inverter-generator, three-phase AC power is converted to direct current (DC) in a rectifier that feeds an internal inverter, which then makes the pure-sine 120-volt 60 Hz AC power to run loads.
The benefit of this system over a standard generator is cleaner, more stable power for all of our sensitive electronics. The engine can be smaller as well, which aids efficiency and quietness.
Add in the EFI, which replaces maintenance-intensive carburetors, and now you have a much more stable and reliable power source.
Cummins Onan QG2500i
In the RV space, generators are often mere inches from the living space, especially in small RVs, making noise and vibration much more noticeable. When Onan designed this generator, they wanted to improve the noise and vibration substantially, make it more reliable, have CAN bus connectivity for modern RV multiplexing systems, and improve fuel economy.
Size, of course, is a concern, and RV manufacturers that include a space or cabinet for a QG series generator use the same size space for this model, so drastically changing the size would be a problem retrofitting older RVs.
The new QGi’s solve many of these concerns. The muffler is contained within the case, adding to the reduced noise factor. In sound chamber testing, the new design provides a reduction of up to 10 dB(A) compared to their already quiet models. That is about a 50% reduction, according to Cummins. At 6-feet from the unit in Cummins’ sound test chamber, ½ load sound intensity was 64 dB(A). The current model is 74 dB(A) at ½ load. For comparison, the National Park Service rules for generators are 60 dB(A) at 50 feet, and a typical RV compartment installation can further reduce noise transmission. Then, to make a good thing better, they offer an optional and easy to install exhaust resonator, which further removes exhaust “pop,” really making this generator purr like a newborn kitten.
Fuel economy has also been improved. While the propane model only gained 20% in testing (1/2 load,) that means increased run time in camp. The gasoline model fared better with a 50% increase during testing. Much of this is from the electronic control system being able to vary the engine speed while not adversely affecting inverter output. Legacy generators will sometimes hunt for the right RPM under load, which wreaks havoc on electronics and causes frequency variances that can cause “the magic smoke” to come out of certain devices.
Lastly, the new QGi is a much easier unit to run and maintain. Where the legacy model required oil level checks every 24-hours, and 150-hour spark arrestor maintenance, the new model electronically monitors engine oil, so no oil level checks between maintenance intervals. There is no maintenance interval for the spark arrestor. It also monitors its temperature, so should it overheat for some reason, it will automatically shut down. Are you traveling up into the mountains? No more elevation adjustments with the EFI with computer-controlled compensation.
Installation
Piece of cake, as they say, with the right equipment. We know most of you probably wouldn’t want to install this on your own, but if you wanted to, you could…it’s pretty straightforward.
We were replacing a vintage Onan Camp Power 2500LP, which initially concerned us because the new QGi has a larger cabinet because of the muffler being inside the case instead of hanging under the unit. Upon further investigation, we found that the Camp Power was installed by a previous owner who had made steel brackets to make up for the size difference. The cabinet was the perfect size for the QGi. The remote switch was wired with a trailer harness cable and was a switch from another brand generator. The 12-volt supply cable couldn’t reach the old generator connection, so they used a nut and bolt to add another (smaller) wire to make up the difference.
A better cob-job couldn’t be found in an Iowa cornfield.
Such is what you find in an RV makeover, so we proceeded to replace and re-route what we needed to. The trailer wiring harness was the right size for the simple remote switch we were installing, so we decided to keep it and splice into it. Otherwise, everything fit like a glove.
Whenever changing a built-in generator, get your hands on a hydraulic table/cart. When having to modify the mounting system, routing cables, fuel lines, and the like, it makes all the difference. Harbor Freight has a good one.
The most significant bit of fabrication we had to do was a custom exhaust pipe. The new QGi has an entirely different type of exhaust system than the old one. Cummins sells different versions of exhaust pipes, with varying drops and lengths. You’re not going to get away without some metal fabrication on this one. Cummins Onan can make a custom pipe, but they’re weeks out. We got one with a 3-inch drop, which wasn’t nearly enough, and a 53” pipe length, which was way too long. Online, we were able to source a 12” Cummins Onan extension pipe to drop out of the genset, cut to length, then cut the other pipe so we could install the optional resonator. Since the new exhaust elbow is included, we made the rest with 3 pieces clamped together, but you can weld it together if you want to.
Operation
Once the unit was installed, we got to test it out, and we were able to experience the difference right off the bat. The old model had a surging idle problem which disappeared under load, but it had much more vibration and noise. When we tested this unit from inside the truck camper, we averaged 74.29 dB(A) on our iPhone with three separate tests. The vibration was also very noticeable. To be fair, the Camp Power is 15 years old with untold hours on it.
After installing the new QG2500i LP, we averaged 58.5 dB(A) on the same iPhone from the same point in the camper. The vibration was noticeably less, and no pop from the exhaust at all. The old Carrier air conditioner bogged down the generator on startup, as expected, but the QGi compensated well. A new electronic A/C easy-start unit would minimize this.
The new QGi was installed with a remote switch in the kitchen, which includes an operation and diagnostic light. We could have also opted for a switch with a Hobbs Clock to keep track of hours for maintenance, or the Energy Command 30 system, which adds auto start/stop and many other functions.
If you’re looking to have a good built-in power source for your small RV that’s quiet, electronics friendly, and reliable, then the new Cummins Onan QG2500i LP is worth considering.
The RV PHD Newsletter is a reader-supported publication. To receive new posts and support my work, consider becoming a free or paid subscriber.
