| Author | Message | ||
| Tom Phillips (Fortyniner)
Registered Member Username: Fortyniner Post Number: 28 Registered: 2-2010 Posted From: 66.93.216.253 Rating: N/A |
So, while Im waiting for some parts I got to thinking about boondock power. My bus has an old diesel AC generator. But AC power usually comes from a big inverter and battery bank. So why dont we replace the AC generator with a big ole 24 volt 50DN and pump up the battery bank when needed? With solar to top it off seems like a good combo. Plus, if you have 24 volt bus it can be charged when OTR. Just thinkin..... -Tom P. | ||
| George M. Todd (George_todd)
Registered Member Username: George_todd Post Number: 1132 Registered: 8-2006 Posted From: 99.180.11.80 Rating: N/A |
Well, lets think some more? Running an average 13,500 BTU roof air from a 24 Volt inverter will pull about 70 Amps out of the battery bank. How many amp-hours is your battery bank rated at? Remembering that only a little more than half is usable, and the faster you use it, even less is available. One horsepower can produce 746 Watts, so a 200 Amp charge at 28 Volts will only take 7.5 Horsepower. The engine will have to turn at least 1200 RPM to produce the 200 Amps mentioned, so we're making a whole lot of noise, and burning a lot of fuel to run the alternator. A small DC generator has been made and tried with success, however it would have to be stowed every time you leave or sleep, to avoid being stolen. An average roof air will consume 1350 Watt-hours on a warm day, which is way more than a roof full of solar panels can produce. These are some of the reasons we do the things we do. | ||
| Don Evans (Doninwa)
Registered Member Username: Doninwa Post Number: 287 Registered: 1-2007 Posted From: 208.81.157.234  Rating: N/A |
The genset also gives you some redundancy. If your inverter or battery bank acts up you have another source of AC. | ||
| Buswarrior (Buswarrior)
Registered Member Username: Buswarrior Post Number: 1940 Registered: 12-2000 Posted From: 174.89.172.13  Rating: N/A |
Yes, Virginia, there is a Santa Claus. There are too few busnuts admitting to doing the DC generator thing, they get picked on. Or, too many busnuts not choosing the DC way, whichever... Every system has the failure point that ends the trip. Nothing wrong with choosing a different failure point? Whether that be the AC generator failure, or the inverter failure, doesn't matter, both need ca$h to fix. Busnuts like to design so that they are able to continue the weekend without running for cover due to a single failure. Perhaps the perfect system would be a lovely little turbo-diesel engine, Kuboto comes to mind, mated to a modest AC generator, say 5K-8K watts, with a big DC alternator, heavy duty style in the 160-200 amp range, suitably 3 stage regulated, AC powering through a classic Trace 4024, with the appropriate controls to keep the pieces from fighting one another, and allow for redundant activation. A religiously designed hush box to keep it all SILENT... A fair sized battery bank to allow longer stretches of QUIET, perhaps 8 golf cart batteries or so... The coach engine keeps the big stock alternator for OTR power. And a couple of high watt solar panels just for fun and storage battery maintenance? What could go wrong that one would not be able to stay functional? Sometimes noisy and less than economical, but functional? With the fancy new generators being DC inverter types... And lots of cheap inverters around...Is DC based power the future? Lots of choices, it's your money to spend! happy coaching! buswarrior | ||
| FAST FRED (Fast_fred)
Registered Member Username: Fast_fred Post Number: 1352 Registered: 10-2006 Posted From: 66.82.9.15  Rating: N/A |
IF you can get by the massive amperage for Air Cond, A big DC alt makes more sense for the boondocker , IF he has lots of batts to charge up. Only a 200+ alt can create the huge DC amperage to rapidly refill a large re charge House demand. AGM would be even faster to charge , but the high cost is a turn off. Since the noisemaker can be run at minor RPM as the charge finishes , the fuel and noise would be at a minimum. FF | ||
| FAST FRED (Fast_fred)
Registered Member Username: Fast_fred Post Number: 1353 Registered: 10-2006 Posted From: 66.82.9.15 Rating: N/A |
You can get by the massive amperage for Air Cond, with DC air cond. A big DC alt makes more sense for the boondocker , IF he has lots of batts to charge up. Only a 200+ alt can create the huge DC amperage to rapidly refill a large re charge House demand. AGM would be even faster to charge , but the high cost is a turn off. Since the noisemaker can be run at minor RPM as the charge finishes , the fuel and noise would be at a minimum. FF | ||
| Jack Fids (Jack_fids)
Registered Member Username: Jack_fids Post Number: 216 Registered: 1-2009 Posted From: 69.171.161.161  Rating: N/A |
I need new bi-focals, I'm seeing double this morning! | ||
| Tom Phillips (Fortyniner)
Registered Member Username: Fortyniner Post Number: 29 Registered: 2-2010 Posted From: 66.93.216.253 Rating: N/A |
That's my thinking. Often the A/C compressor cycles in moderate weather. The generator could run just fast enough to supply the average power. Would the speed control simply try to maintain 29 volts? As far a redundancy goes if you have dual A/Cs then dual inverters is not out of the question. Maybe one big and one medium. And many buses already have big alternators which provides dual DC supplies. Going further, how about capturing the waste heat from the generator motor for hot water. One way to do that might be with an exhaust diverter to direct exhaust through a heat exchanger when desired or bypass it otherwise. | ||
| George M. Todd (George_todd)
Registered Member Username: George_todd Post Number: 1137 Registered: 8-2006 Posted From: 99.48.212.158 Rating: N/A |
About a year and a half ago, JohnMC9 posted an EXCELLENT article on batteries. It in the archives, and well worth reading. One of the most important points was that batteries are not gas tanks-you just can't fill them up in 10 minutes when they're empty. 29 Volts is too high for long battery life, it will burn water out of a bank quickly. Generating DC to use as AC thru an inverter will result in a 15 to 20% efficiency loss, so I would use my AC gen to power the Air Conditioning, and let the inverter charge the batteries. There are several heat exchanger water heaters available now, which use the engine coolant as the heat-carrying media. Couple the genset cooling system to the bus radiator, and you have the cheapest remote radiator made. You will probably have to add a small 12 Volt fan to the engine radiator for heavy loads. Then you will OTR and arrive with free hot water, and have free hot water all the time the gen is running. With a Webasto plumbed in, you have your water heat, space heat, and quick block heat all in one system. |