I've been wanting to comment on a number of small items in this thread:
Moondawg wrote:... Would most appreciate suggestion/s as to an effective power backup for my CPAP plus Humidifier. ... I HOPE the answer is not a deep cell marine battery!
The term "marine" is a red herring. A backup battery MUST be DEEP CYCLE. Some marine batteries are, some are not. The only reason marine gets mentioned is that the most bang for the buck (i.e. the most AmpHours per dollar) is with a Walmart etc. marine deep cycle which can be had for about $80 for 100 Amp Hours. These are quite popular with weekend fishermen but long distance cruisers who are cycling their batteries every day use industrial style batteries from quality companies like Trojan. I get my batteries from a golf cart supply company.
Pugsy wrote:...The 60series machines use more power.
I thought the conclusion from the JohnO thread was that the C9 used more power than the Series 60.
raftergirl wrote:Thanks for that link to the Owell battery Pugsy. I had not read that thread before, and was amazed at the hours he got from it. Way more than what the website predicted based on pressure settings.
Unfortunately there is a serious problem with the data supplied by JohnO in the thread. Although he is emphatic that this included the humidifier, he admits in a later post the the room was well humidified by a whole house humidifier. Since the Series 60 senses the ambient humidity, it probably never turned on. In his words: "My room is pretty well humidified." The Owell battery is about 20 AmpHours, so there's no surprise that it could run 4 or 5 nights at modest pressures. But if it tried to humidify in a dry environment it would be dead in one night.
raftergirl wrote:Here's another alternative. I was given this link by another rafter who uses cpap. These batteries [LiFePO] might be a good compromise. Not quite as expensive as the Li Ion, but much lighter and slightly smaller than my Deep Cycle AGM. 6.6 lb. for the 12V20A vs mine at 13 lb. Another plus is that they are much better suited to being discharged below 50% vs the AGM batteries, and they have a much longer lifetime of charging. I might think about one of these in the 12A version (3 lb.) for my kayak touring where I definitely need a smaller & lighter battery. Perhaps I'll replace all my AGM with these in the future????
Its true that AGM batteries do not like being discharged to zero, but a quality AGM such as a Trojan can handle 500 cycles down to 20%. This is far more than the average user would expect with occasional backup service. For the price of one 20 AmpHour Lithium battery, one can get 80-100 AmpHours of Trojan AGM power. Of course, the Lithium battery will be 5-7 pounds, while the AGM will be 50-60 pounds - this will be significant for kayaking, but not for home backup.
Since running with real humidity will take at least 20-25 AmpHours a night, a backup that can handle a few nights in nasty conditions (ice storm, hurricane, etc) should be 50 AmpHours or more. I don't know what objection the original poster (Moondawg) has to "deep cell marine" - if its weight then Lithium is the answer, but the cost runs $250-300 for even 20 AmpHours. If its the mess of a cheap flooded battery, then the AGM is reasonable and but will cost more. Raftergirl's multible 20AH AGM solution works for her particular issue of minimizing weight while providing flexibity, but for home use a single battery sized for the expected need is much better. (Other than weight issues, its generally best to oversize batteries - they charge faster and last longer.) My home solution is a small AGM that sees more service as a hobby power supply, and can be recharged with my portable generator if needed for more than a night. But I don't need humidity so I can get away with only 20 AH; if you need more, a quality 80 AH AGM such as a Trojan is about $240.
BTW, I generally don't worry about humidity because in my part of the country (coastal New England) the biggest risk for extended power outage is a hurricane, which usually brings humidity. However, if your worry is ice storms, humidity is an issue.
