noahwf wrote:I have both sleep apnea and a heart condition, and I already have a pretty pricey battery for the scooter I use due to the heart condition. The owner's manual says it is "25.2V 11.25Ah Li-Ion" and the website says it's "274WH":
https://shop.travelscoot.com/us/accesso ... 283wh.html
I'd like to go camping with my family, and I'm wondering if I can use the scooter battery with my CPAP (a ResMed) without the humidifier. I'm guessing there will be at most 3-4 days of camping in any one place, after which we'll drive to another place.
Specifically, I'm wondering if it would work to:
- Buy the ResMed DC/DC converter
- Figure out some way to connect between the scooter battery's flat connector and the CPAP plug (any suggestions here would be great)
- Use a car inverter and the charger that came with the scooter to charge the battery on driving days
Any advice would be appreciated!
Happy New Year and Welcome to the group!
You've asked a good question with several interesting aspects.
First, assuming you have a modern ResMed device, you'll want the ResMed DC Converter for your pump (about $85) because it has the proprietary ResMed plug and circuitry that sends a signal to the pump. (The plug comes on the ResMed AC supplies, the DC Converter, and a few custom battery systems.) Its a little known fact that the converter works fine with 24 Volt sources such as your battery, as well as more common 12 Volt sources.
Second, you have to consider whether the battery is sufficient for your needs. Normally I do these calculations in 12 volt amp-hours, but for this case I'll use Watt-hours. Normal 8-hour usage for modern ResMed and Respironics pumps is 40 to 100 Watt-hours depending on the settings, the leak rate, and the altitude. I figure about 50 Watt-hours for my Respironics 560 at pressure 10 at sea-level. So your 4 night trip could be about 200 watt-hours assuming similar usage. This is well within the rating of your battery.
You don't mention the type of connectors for the battery. Many batteries this size use "lugs" that can be easily bolted to a connector like this:
https://www.amazon.com/Battery-Tender-0 ... B004JV6OMO
Which can connect to a socket such as:
https://www.amazon.com/Battery-Tender-0 ... B0041CDPQO
Care must be taken that no one uses the socket assuming its a normal 12V supply, as it ill be 24V. You should put a serious warning label on it!
If your battery doesn't allow connecting with a ring, you'll have find an alternative, but anyone handy with electrical stuff (including many boat owners and computer or ham radio hackers, etc.) should be able to help. You could take the ring connector I listed to a Radio Shack (if you can find one) and they would probably crimp on the right connector for the cost of a six-pack.
Your thought of charging with an inverter running from the car is workable but has a few issues. One is that its rather inefficient, so it will cost twice as much power as you used. This is not a problem if the engine is running, but if you tried to do a complete recharge without the engine, you could easily drop the battery below the point where it can start the engine. The second issue is that a full recharge takes about 5 hours, and you probably don't want to leave the car running all day at the campsite. On the other hand, if you were going out for an hour drive during the day, plugging the battery into an inverter/charger setup could add significant juice to the battery, stretching out the time the battery can cover.
I would be remiss if I did not point out a more cost effective alternative: A U1 AGM scooter battery provides 35 amp-hours, which is about 420 watt-hours. The AGM is a bit less forgiving of deep discharge than the Lithium, so you might consider them the same useful capacity. The AGM is about $65 compared to the $800 (with shipping) of the Lithium pack. The downside of course is that the AGM is 24 pounds, while the Lithium is about 4 pounds. AGMs come in a variety of sizes, so if you had several, you could put on the same quick-connect cables (as listed above), use the same charger and swap them as needed.
