Charge spare battery

mobeewan wrote:
The ResMed 12v to 24v converters are not just 12v to 24v generic power converters. They are made for the ResMed CPAPs and only support one machine. There are 3 parts. The 12 to 24 volt brick portion that has a cable that plugs into the CPAP. The plug is a propritary 3 pin plug. The same plug as on the 120v AC to 24v DC brick. The other 2 parts for the 12v to 24v converter are cables. One cable that plugs into the brick and has battery clips. Another cable that plugs into the brick and has a male cigarette lighter plug.

exactly. Although you do NOT need to buy the 12-24V converters from resmed. Battery power solutions also makes one that is compatible, you need to specify which resmed you have. The Battery power solutions unit is what I use. has worked fine for 2 years so far, 3months or more/year. At the time it was much less expensive than the resmed unit. Don't have current prices to compare.

The ResMed 12v to 24v converters are not just 12v to 24v generic power converters. They are made for the ResMed CPAPs and only support one machine. There are 3 parts. The 12 to 24 volt brick portion that has a cable that plugs into the CPAP. The plug is a propritary 3 pin plug. The same plug as on the 120v AC to 24v DC brick. The other 2 parts for the 12v to 24v converter are cables. One cable that plugs into the brick and has battery clips. Another cable that plugs into the brick and has a male cigarette lighter plug.

It may have been better to order a single 12 to 24 converter that was large enough to power both units.

K_and_I wrote:
I just ordered the 12 to 24 adapters for both my wife and I. Cost was more than I wanted to spend, but hopefully over enough time it will make sense. I did see Resmed's pdf on power inverters, and used it to size the battery I bought.
Thanks again for your help.

mobeewan wrote:


I don't really know what the exact efficiencies are one versus the other, but you do lose about 10% going from DC to AC with an inverter. Then with the inverter you going back to DC at 24 volts and there's probably an efficiency loss there. With the rest Med converter you're only making one change from 12 volt to 24 volt so I would think that it would have to be more efficient overall. So far I've only used the CPAP while tent camping at a campground it did not have power and I brought my own 12 volt DC deep cycle batteries. My camping times have been limited to three nights and I've used both the inverter and then later the power adapter when i received it. I've always had power left on the battery with the inverter or the DC converter after three nights and I've used the humidifier every time. Res meds website has a PDF for using power inverters with their equipment you might take a look at it.

I just ordered the 12 to 24 adapters for both my wife and I. Cost was more than I wanted to spend, but hopefully over enough time it will make sense. I did see Resmed's pdf on power inverters, and used it to size the battery I bought.
Thanks again for your help.

K_and_I wrote:

mobeewan wrote:

ResMed also makes 12v DC to 24v DC converter (brick with cable that connects to CPAP) that comes with two different cables to connect between the brick and 12 volt source. One cable has battery clamps the other has a cigarette lighter plug. My medical equipment provider kept telling me that insurance didn't pay for it. At the time I had an Anthem EPO (premium) plan that provided 100% payment on medical equipment. I contacted Anthem and they said they would pay for the converter under my plan since I had 100% coverage provided I had a note from the doctor saying it was necessary. I told respiratory doctor I needed it when I went camping and he provided the note on a prescription pad for me which I turned in. Insurance paid for it. I Have used it on trips with 6 hours sleep per night for 3 nights using the humidifier. I used a spare Walmart group 27 EverStart 27DC deep cycle battery used for CPAP only. Still showed over 12 volts on the battery after I got home. So it would probably last me 4 nights at 8 hrs per night or 6 nights at 6 hrs per night.

Now there is an angle that might work. I don't think I have 100% medical device coverage, but I think I'm going to have unused Health Care Spending Account money at the end of the year. Any idea how much more efficient it is to convert from 12v DC to 24v DC instead of 12v DC to 120v AC back to 24v DC? That increased efficiency might allow us to use the humidifiers. The battery I have is a 55Ah AGM deep cycle solar power battery. So far, we have not been without plug ins for more than one night.
Again, thanks to all for responding.

I don't really know what the exact efficiencies are one versus the other, but you do lose about 10% going from DC to AC with an inverter. Then with the inverter you going back to DC at 24 volts and there's probably an efficiency loss there. With the rest Med converter you're only making one change from 12 volt to 24 volt so I would think that it would have to be more efficient overall. So far I've only used the CPAP while tent camping at a campground it did not have power and I brought my own 12 volt DC deep cycle batteries. My camping times have been limited to three nights and I've used both the inverter and then later the power adapter when i received it. I've always had power left on the battery with the inverter or the DC converter after three nights and I've used the humidifier every time. Res meds website has a PDF for using power inverters with their equipment you might take a look at it.

ktmrfs wrote:
BTW the resmed ONLY runs on 24VDC ALL the time,

There are different models of Resmed's.
Mine actually runs on 12 V......because I insisted on that when I got it.

ktmrfs wrote:

how much more efficient I don't know. but the std resmed 120V to 24F DC brick based on spec's is not overly efficient.

my experience is that using a efficient PSW inverter 150W or so max input instead of 12-24VDC bps brick I got 2 days with the inverter and back vs 3 days with the dc to dc converter.

but the humidifier can be a real power hog. depends on ambient temps, humidity levels, breathing rate etc. but it can easily triple the power draw.

a better alternative if you want humidifier is to just fill the reservoir but turn off the humidifier function. start with warm water and you will have a pass through humidifier function.

often works quite well.

It sounds like, from you experience, perhaps a 1/3 improvement in efficiency. It might be worth the cost of the 12 to 24 adapter. We can live without humidification for a night if needed.
Thanks again for the info.

K_and_I wrote:

mobeewan wrote:

ResMed also makes 12v DC to 24v DC converter (brick with cable that connects to CPAP) that comes with two different cables to connect between the brick and 12 volt source. One cable has battery clamps the other has a cigarette lighter plug. My medical equipment provider kept telling me that insurance didn't pay for it. At the time I had an Anthem EPO (premium) plan that provided 100% payment on medical equipment. I contacted Anthem and they said they would pay for the converter under my plan since I had 100% coverage provided I had a note from the doctor saying it was necessary. I told respiratory doctor I needed it when I went camping and he provided the note on a prescription pad for me which I turned in. Insurance paid for it. I Have used it on trips with 6 hours sleep per night for 3 nights using the humidifier. I used a spare Walmart group 27 EverStart 27DC deep cycle battery used for CPAP only. Still showed over 12 volts on the battery after I got home. So it would probably last me 4 nights at 8 hrs per night or 6 nights at 6 hrs per night.

Now there is an angle that might work. I don't think I have 100% medical device coverage, but I think I'm going to have unused Health Care Spending Account money at the end of the year. Any idea how much more efficient it is to convert from 12v DC to 24v DC instead of 12v DC to 120v AC back to 24v DC? That increased efficiency might allow us to use the humidifiers. The battery I have is a 55Ah AGM deep cycle solar power battery. So far, we have not been without plug ins for more than one night.
Again, thanks to all for responding.

how much more efficient I don't know. but the std resmed 120V to 24F DC brick based on spec's is not overly efficient.

my experience is that using a efficient PSW inverter 150W or so max input instead of 12-24VDC bps brick I got 2 days with the inverter and back vs 3 days with the dc to dc converter.

but the humidifier can be a real power hog. depends on ambient temps, humidity levels, breathing rate etc. but it can easily triple the power draw.

a better alternative if you want humidifier is to just fill the reservoir but turn off the humidifier function. start with warm water and you will have a pass through humidifier function.

often works quite well.

mobeewan wrote:

ResMed also makes 12v DC to 24v DC converter (brick with cable that connects to CPAP) that comes with two different cables to connect between the brick and 12 volt source. One cable has battery clamps the other has a cigarette lighter plug. My medical equipment provider kept telling me that insurance didn't pay for it. At the time I had an Anthem EPO (premium) plan that provided 100% payment on medical equipment. I contacted Anthem and they said they would pay for the converter under my plan since I had 100% coverage provided I had a note from the doctor saying it was necessary. I told respiratory doctor I needed it when I went camping and he provided the note on a prescription pad for me which I turned in. Insurance paid for it. I Have used it on trips with 6 hours sleep per night for 3 nights using the humidifier. I used a spare Walmart group 27 EverStart 27DC deep cycle battery used for CPAP only. Still showed over 12 volts on the battery after I got home. So it would probably last me 4 nights at 8 hrs per night or 6 nights at 6 hrs per night.

Now there is an angle that might work. I don't think I have 100% medical device coverage, but I think I'm going to have unused Health Care Spending Account money at the end of the year. Any idea how much more efficient it is to convert from 12v DC to 24v DC instead of 12v DC to 120v AC back to 24v DC? That increased efficiency might allow us to use the humidifiers. The battery I have is a 55Ah AGM deep cycle solar power battery. So far, we have not been without plug ins for more than one night.
Again, thanks to all for responding.

ktmrfs wrote:

K_and_I wrote:
Thanks again for the replies. They are Resmed CPAPs and use 24 volts. We do plan to turn off the humidifiers- that is the basis of the calculations I used to size the battery. Things may change in the future, but for now, I just need 1 night's worth of use at a time. We do not boondock for more than 1 night without a plug in between.

ok battery power solutions makes a 12 to 24V dc to dc converter for the resmeds. BTW the resmed ONLY runs on 24VDC ALL the time, the wall plug brick converts 120V to 24VDC. cost of the bps converter is around $50 IIRC. Once you turn OFF the humidifier AND use airplane mode, the resmed will draw less than 1A. that's 8AH or less per night. even with two at 16AH/night and a single 75AH battery you should be able to go 3-4 nights before needing to recharge.

ResMed also makes 12v DC to 24v DC converter (brick with cable that connects to CPAP) that comes with two different cables to connect between the brick and 12 volt source. One cable has battery clamps the other has a cigarette lighter plug. My medical equipment provider kept telling me that insurance didn't pay for it. At the time I had an Anthem EPO (premium) plan that provided 100% payment on medical equipment. I contacted Anthem and they said they would pay for the converter under my plan since I had 100% coverage provided I had a note from the doctor saying it was necessary. I told respiratory doctor I needed it when I went camping and he provided the note on a prescription pad for me which I turned in. Insurance paid for it. I Have used it on trips with 6 hours sleep per night for 3 nights using the humidifier. I used a spare Walmart group 27 EverStart 27DC deep cycle battery used for CPAP only. Still showed over 12 volts on the battery after I got home. So it would probably last me 4 nights at 8 hrs per night or 6 nights at 6 hrs per night.