Model DCR50 Refrigerator
Old Dave's ticker has actually stopped twice. He loves to fish and is now willing to do whatever it takes to preserve his health.
Note that this kind of system could be critical to a mandatory CPAP wearer in the event of a prolonged power outage due to storms or other disasters.
If you are a mandatory CPAP wearer, please read the rest of this story. It might save your life some day!
Dave asked me, if he wanted to take an extended river trip or another of his famous wilderness adventures (I have gone on two with him), "What would it take to run a CPAP from solar power?"
Dave sent me the specs on his unit, a BiPAP AutoSV with memory card by Respironics. He gave me the electrical specifications from the manual:
AC Voltage source 100 to 240 VAC, 50/60Hz
DC Voltage Source 12 VDC (when operated with the external DC power adaptor accessory
AC Current 1.25 A Maximum
DC Current 3.0 A Maximum
Perfect, that's e system it will take to run the unit for 8 hours a night.
Here are the calculations:
Volts x Amps = Watts
So, 12 volts x 3.0 amps = 36 watts for one hour of operation and we need to run for 8 hours for a good night's sleep. We have looked at other CPAP units that require only 30 watts per hour. Running on a low voltage power supply will be helpful so that no inverter is required.
The energy consumption of 36 watt-hours x 8 hours = 288 watt-hours. Taking into consideration a discount factor for battery inefficiency, we need about 150 amps for the battery.
Most standard 12 volt deep draw marine batteries are in this size range, 110-130 amp hours rated at a 20 hour discharge rate. A 153 amp AGM Sun Xtender would be a wiser choice. If more autonomy is required, it might take a larger battery.
For the solar panel size, with 4 peak sun hours of recharge time per day (typical of his area of Montana) = 10 peak amps needed from the solar panels. Depending on the panel efficiency (how many amps per square foot they will produce), the solar panels need to be about 200 watts at 12 volts. That’s one each 200 watt panel measuring more or less 65 x 36 inches each, weighing about 40 pounds each.
What's the Cost?
There is no affordable way to do this with flexible panels which would make the system more compact and portable so Dave's system is not likely to be river raft or drift boat portable. But, if he was fishing from a base camp, it would fit in his vehicle and he could set it up at camp, let the sun shine while he fishes, and have a safe and restful sleep.
The estimated cost for a complete system should be less than $2,000 depending on the model of the charge controller and the features it has, and the efficiency of the solar panels.
If you are a wilderness or outdoor lover who camps in places without grid power, this system will work for you. If you are a mandatory CPAP wearer, having emergency power for your CPAP could save your life. You might talk to your doctor about prescribing this system as a requirement.
You may already have battery backup that runs off the grid, this is good, but will not be so good if the power stays off for five and a half days like it did during a recent ice storm. You may have a generator. This is also good, but not so good if you run out of fuel and cannot resupply, like some of the folks involved in the Nashville flood of 2010.
If you need emergency backup power for your CPAP or any other medical device, we would be pleased to work up the requirements like we have for Old Dave. Get your electrical specifications together and all you have to do is ask. Call or contact us today.