I'm gleaning through several threads to compile this data.
If your CPAP unit has a 12VDC power supply, great ! If you don't need the humidifier, even better, you will likely be able to lift the battery pack.
The medical supply shops will gladly sell you a sexy Lithium battery, that will only last you two or three nights before needing recharge. (but no humidifier with them either)
You can lug around a Group 24 Marine battery ($100) and wire a cigarette lighter to plug the CPAP automotive cord into. That will get you 3 or 4 days before you HAVE to recharge it.
Or, I found a suitably sized Jump Start power pack (battery booster) that had a cigarette lighter on it's front panel. Uses a wall wart to recharge from AC power, and it came with a automobile charge cord to recharge from while driving. (Or I can charge it from a solar panel.)
What you need to do, is to discover how much power the machine consumes overnight, and obtain a battery that can supply at least twice that much power for a night (only drains the battery 50%). Draining a battery more than 50% really shortens it life from hundreds of cycles, to less than a hundred.
The math. You want to calculate power in Watt Hours. 45watts * 6 hours = 270 wh
Look at the CPAP or it's power brick. Does it list wattage ? 3A at 12VDC ? 1A at 120VAC Volts * Amps = watts,
so 3 * 12 = 36w * 6 hr = 216wh
Same for batteries, a 20Ah rated battery * 12V = 240 total watt hours in it, 120 of which are useable for long lifetime. So this
little exercise shows that your really need a 40ah battery for this CPAP machine. I got liucky, my 18ah battery will run my machine (sans humidifier) for 2 days @ 10" pressure, before I need a recharge.
So give it a try, and see what works for you. And you can jumpstart the car with it too!
If your CPAP unit has a 12VDC power supply, great ! If you don't need the humidifier, even better, you will likely be able to lift the battery pack.
The medical supply shops will gladly sell you a sexy Lithium battery, that will only last you two or three nights before needing recharge. (but no humidifier with them either)
You can lug around a Group 24 Marine battery ($100) and wire a cigarette lighter to plug the CPAP automotive cord into. That will get you 3 or 4 days before you HAVE to recharge it.
Or, I found a suitably sized Jump Start power pack (battery booster) that had a cigarette lighter on it's front panel. Uses a wall wart to recharge from AC power, and it came with a automobile charge cord to recharge from while driving. (Or I can charge it from a solar panel.)
What you need to do, is to discover how much power the machine consumes overnight, and obtain a battery that can supply at least twice that much power for a night (only drains the battery 50%). Draining a battery more than 50% really shortens it life from hundreds of cycles, to less than a hundred.
The math. You want to calculate power in Watt Hours. 45watts * 6 hours = 270 wh
Look at the CPAP or it's power brick. Does it list wattage ? 3A at 12VDC ? 1A at 120VAC Volts * Amps = watts,
so 3 * 12 = 36w * 6 hr = 216wh
Same for batteries, a 20Ah rated battery * 12V = 240 total watt hours in it, 120 of which are useable for long lifetime. So this
little exercise shows that your really need a 40ah battery for this CPAP machine. I got liucky, my 18ah battery will run my machine (sans humidifier) for 2 days @ 10" pressure, before I need a recharge.
So give it a try, and see what works for you. And you can jumpstart the car with it too!
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