Lithium battery for CPAP machine

gobi

Member
I wanted to use my ResMed while I on the road.

I started out with this solution:

1. 12 Volt ResMed power adapter (bought online)
2. A 90ah vehicle starting battery I had laying around.

Worked but heavy - The 31d battery worked fine for 3 nights of use, but that thing was heavy, and I had to take it out of the van to charge it.

After I had to lift and move it few times I was ready for a lighter solution.
I bought a 100ah Litto Kala lifepo4 battery (well I made it myself :) )

ResMed CPAP > 12 Volt Power Adapter > 12v 100ah Lithium battery

Next in my list is to set up a charging link so I can use it to charge the 100ah Lifepo4 battery from my van's alternator.
I will be charging @ 10a max.
The 100 ah battery is used to power my laptop using a small 200w inverter. So this little battery gets a lot of use.
 
Nice 👍. My dad used to have one of these machines. He had a plug that plugged into the cigarette lighter for his so he could use it in his truck when he slept at night. Smart idea.
 

gobi

Member
Thread starter
Was that out of a jump-starter?
lol, no, I had a smaller AGM batt (acdelco) that died under warranty, took it to the distributor and he did not have a little one, instead paid the diff (30$) for the biggest baddest AGM they had in stock :)
 

gobi

Member
Thread starter
Auto, but I was shocked they had this in stock and it was fresh stock.
The weight just makes it a semi portable unit.

batt_agm.jpg
 

gobi

Member
Thread starter
Which battery to get for CPAP machine is a subject that we all have stumble with.

First let's look at 8 hours of use at 8 pressure setting and 6 Humidity setting.

Average AH need for this use for 1 night = 20 to 25 AH @ 13v

Lithium batteries give us around 80% usable capacity.

So, I went with a 100 AH @ 13v lithium battery. This will give me 3 days of use before I have to charge it.

So what are the choices out there:

1. If you are handy, buy 100 ah littokala cells off aliexpress and add your own BMS = total cost $200, this is the route I went.
2. Buy a 100 ah @13v premade battery off Amazon, Miady or any of the popular inexpensive brands.
 

gobi

Member
Thread starter
For dry camping and for travelling down south to fish in my van camper, I wanted to figure out the optimal size for my battery for CPAP machine in my camper.

I bought a factory (RESMED) 12v power supply for my CPAP as I did not want to buy an inverter and use the 120v power supply that came with the CPAP.

I sleep 6 to 8 hours on average, so using a killwatt meter I figure out max around 300wh

How much battery for 1 night:
300wh/14 = 21 ah at 14v,

14 volt is the output of a LIFEPO4 12v battery give or take 0.5 volts.

So a 50ah 12v LIFEPO4 battery will be sufficient for 2 night and then recharged.

My go to LIFEPO4 battery right now is a 100ah 12 battery.

I have attached a pic of the RESMED12v power supply, is comes with 12 female cigarette receptacle that has rings to be connected to a battery.
 

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