Sorry I missed this post until the thread got bumped - I certainly would have replied if I had seen it.herefishy wrote:n reference to my earlier post about my batteries being discharged after one night on the old respironics cpap, i have 2 Kyocera solar panels(80 & 75 watt), a pair of Concorde AGM 6 volt 220 ah batteries, an Intellipower PD9145A converter along with a Charge Wizard. I have a cigarette lighter outlet so I can plug the cpap directly into the battery system, so am i wrong to expect 10 amps x 9 hours or 90 ah x 2 x 220 or at least 4 nights out of the system?
So the quick answer is if you really have a 10 Amp load it won't go 4 nights. Your batteries are 6 volt so two in series will give 12 Volts with 220 Amp-hours capacity. If you want to get long life from your investment, you should limit the use to 50% or 110 Amp-hours. If you have limited recharging opportunities, it may be difficult to "top off" the batteries. I figure I often recharge my boat batteries only to 85%. This means I plan on a useful range of 50 to 85% or about a third of the actual power. If you can plug in or drive for 5 hours or more you should be fully charged. So you should figure roughly 80 to 100 Amp-hours available.
What I don't understand is where you get the "10 Amps" number. A Respironics 560 pump will use roughly 0.5 Amps or about 5 Amp-hours a night. If you use humidity/heated hose you still should be under 35 Amp-hours worst case. If you have an older model perhaps the usage is higher. Also, I assume when you say "plug the cpap directly into 12V" you mean you have the 12V adapter cable and nothing else is running, no inverter, charge controller, etc.
Looking at your solar panels - You have 155 Watts of solar. This could provide about 10-11 Amps of charging current (more likely around 5). To figure daily charge you have to look on charts for the region and season, but basically you figure about the equivalent of 3-4 hours of good charging (more in summer and sunny areas, less in winter and cloudy, etc) So figure about 30 to 40 Amp-hours a day. However, this assumes no shading from trees and reasonable weather. This is a problem with solar - we tend to park RVs in shady places, and hunker down in stormy weather; its never as productive as you might hope.
So bottom line: your pump should only be a small load. The batteries fully charged should have enough juice to run the pump several weeks, humidity for at least 4 nights. The solar panels should be able to recover your daily use. (If its clear and dry so you need humidity, the panels should produce; if its cloudy you probably can do without humidity.) I don't see any reason why your system shouldn't work.
So what can go wrong? First, it would be nice to know the model cpap, the power setup, and the humidity needs. This way we can figure the true load.
I would consider a few questions:
Are the batteries fully charged? Are they more than 5 years old, or have they been abused? Your charge controller looks pretty good. But if you've killed the batteries more that a couple of times they could have a permanent issue.
Is there bad wiring? The meter on my panels said over 5 amps. but I found a corroded wire that dropped the voltage at the battery below the charging level. Problems like this can, and will, occur anywhere along the line, so you should get a good voltmeter and test daily. And don't just test at one spot, or rely on one system meter; you should test every outlet, and every connection.
I was also curious what else is on the circuit? Old incandescent bulbs can easily be more than the cpap. A 12 Watt bulb (pretty small) is a 1 Amp load, double most pumps! Running a few of these for a couple of hours is more than the pump overnight. Also, a computer or a small TV is easily much more than the pump. My families full complement of cell phones and iPods equal my pump's load! So if you walk around the RV and think "this is nothing" and "that is nothing," a lot of nothings add up. If you have a big inverter its standby load could be more than the pump uses. If you have a "dual mode" fridge it might be in the wrong mode, using electricity when you expect it to use propane.
The list of possibilities is long. The thing I try to remember in these situations is "The one thing I know for sure is that something I know for sure is wrong." In other words, some basic assumption is faulty - something you think can't fail did.
