After my daughter spent a small fortune on a battery for her CPAP machine so she can go camping and the damn thing has an 8-hour life, I figured there must be a better way.
I thought a 100 amp LiFeO4 battery with a 300 watt pure sine inverter would last a lot longer and for not much more than the cost of portable set up she bought.
I know she'll also need a charger but would like to know how others have managed.
24 Volt battery it seems.
Its a nightmare actually. The trouble with CPAPs is you get used to having one and when you sleep without one it's a nightmare. Literally. I looked into buying one of the two or three that will work off a battery (just a 12 volt one, not a battery pack) and it is expensive to buy a whole new machine and a lithium just for the few nights I go away from 240v. I absolutely hare being so dependant on it, especially going anywhere means packing up and taking your unit with you., setting it up etc etc. Hate the bloody thing but I do sleep better with it unfortunately.
Thanks Sheik. Unfortunately my daughter is going camping 2nd week of the school holidays and so she went ahead and bought a battery pack operated one. To complicate matters the mask she has doesn’t fit and another $180 needed for a new one that she doesn’t like.
Seeing the dependence on these devices by so many people CPAP manufacturers certainly have a captured market and don’t make things easy.
My initial thought was as per my first post as at that stage I wasn’t aware of the fact that she’d purchased the new machine and what the voltages involved were. I’ve since determined that the 240v machine steps down to 24v to operate and the battery operated one works off a 24v LiON 16050 milli amp battery.
This camp has power so she can recharge daily but most other camps she goes to (they are all pet friendly) don’t, which is why I was looking for alternatives. So here are my options as my non electrical brain can manage.
1. As per my initial post, 12v 110amp lithium battery, 300w pure sine inverter. Should easily last 4 to 5 days. Doesn’t need the battery operated machine but then needs a charger etc to recharge at home. Might even get her money back on the second unit.
2. A 24v LiFeO4 battery, just need a few fittings, same issues as above plus as it comes in at 25.5 volts charged will there be similar problems the early leccy motors suffered due to high continuous charge. Also 24v models are far more expensive than option 1.
I haven’t even looked at solar charging as generally in the past camps that she’s been there hasn’t been enough open areas to set up a system.
I know of a couple of guys dependant on them but they use them on boats so have the facilities to recharge.
As you say, it’ a nightmare, sounds like a business opportunity for someone.
In previous years we did some 4wd bus and camping tours in the Kimberley’s. The only way for us was if the tour company charged batteries for her each day. Worked on the first trip. Failed on the second because they took two fully charged batteries with no way to charge them. They thought that would be plenty of power for 5 nights. Wrong.
I have recently been looking at similar tours around Central Australia. None of the companies cater for recharging during the day. Frustrating because it limits us to blacktop tours and motel stays. Is she driving and camping? Can she carry solar or small genny.
Ok, I got it wrong, she just bought a battery pack and as her old mask had cracked couldn't get the same as replacement. Still $600 all up and hasn't solved the problem.
Gunna, she has car access to her spots as she and her friends take their dogs.
Solar just hasn't worked in the past due to too much shade where they go. One trip I went on and had to go for a drive to a nearby town to top up my deep cycle battery as the solar didn't work enough.
A small genny may be an option but it takes 3 hours to charge that small 16 amp battery and requires carrying even more gear.
It is a logistical nightmare.
Forgot to add, genny's banned in a lot of camping grounds.
Dignity, I have the same battery pack but haven’t tested it yet. I have used a small inverter off a 120amp itechworld lithium for a couple of nights and that worked perfectly. I’ll be camping at Fraser for a week in May and intend using the same set up. I will have a 1kva genny too just in case. Other thing is to disable the humidifier if she uses that as the air hose is heated when humidifier is in use, and that obviously draws more power.
CPAP is a pain, but then it is a lifesaver too. I don’t go anywhere without mine, not even for a night as my sleep quality is so poor without it.
regards
dave.
What is the power draw of a CPAP machine ?Originally Posted by Dignity
Why not look at a dual battery (125 amp LiFePO4) for the car with DCDC charging & have an appropriate inverter . That way when you run the car you are charging at a high rate (40amps). ..... I'm assuming that they would go for a drive every day.
That will eliminate the reliance on solar (unreliable) or a genny (which may not be allowed)
Chris
Give a man a fish & he will eat for a day !
Teach him how to fish
& he will sit in a boat - & drink beer all day!
TEAM MOJIKO
Thanks Dave, I'm thinking that will be the wsy to go as the cost of a e4 volt LiFeO4 is prhobitive for her and I think a dc-dc step up/step down charger needed to dtabilise input.
Edit: And this morning she just tested positive so I can't visit and I'm wondering will that machine just keep rolling that virus around and around.
Chris, apparently according to the docs it's 53W with a peak of 104W. She is a single school teacher so her funds are limited and I expect that could be a solution although she is already complaining there isn't enough space in her car now. So I guess we'll try and keep it as simple as possible in the short term and progress from there.
These girls rarely drive once they set up camp but take long walks.
Dave, I spoke with my BIL who has a bit of electrickery knowledge and worked out a working solution. As each conversion has a loss of efficiency, lets say around 5%-6% or sometimes more but we will assume 5% for convenience, this is what will drive the end solution, so here is our thinking.
- As the CPAP machine uses 240V input but then steps it down to 24V %5 loss.
- The pure sine inverter converting from 12V to 240V - 5% loss
This means there are 2 losses and therefore less efficiency.
So the battery pack provided by your CPAP provider powers directly into the machine - no loss. Then we would:
- use a 12V to 24V DC-DC converter - 5% loss
This should extend battery life just enough and also put only 24V into the machine When I can get down to see her after her isolation I will make up a lead to be able to put some tongs on to check actual amp draw which I will let you know.
Now our combined thoughts could be well out of the ball park.
Cheers
Sam
It is a bloody nightmare, but yes asmentioned above , make sure humidifier is switched off as this drags power. If she hasnt tried the nasal pillows rather than the full face mask then try that as I found a massive improvement. Not everybody does of course.
Had to visit my daughter early in the week so took down my 97amp deep cycle AGM from the leccy motor my 300W 240v inverter and plugged my in-line watt meter in for a test run. She used the CPAP machine with humififier from 10pm to 7am with no issues.
The watt meter showed the battery voltage had dropped from 12.8V 12.5V and 21.9 amps usage.
I thought that was reasonable for an AGM that I bought in Nov 2015 and has had a significant amount of use with the leccy.
I'm just waiting on the plug for the 24V side of things (Medres don't make it easy or cheap) before I try my other option.
I'll be very interested in Alchemy's experience next month.
Dave, how did your week at Fraser go and what did you suss out with battery life using the CPAP machine.
Cheers
Sam
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