CPAP and Inverter advice needed




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  1. #1
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    Default CPAP and Inverter advice needed

    Hi,

    I have been using a CPAP device for about 18 years and my first two devices had a 12v option for when I go camping. No problem.

    My new device doesn't have a 12v plug/option and runs through an AC/DC Adapter with a 24v/2.5A output.

    I have used the device with a 350w Pro User modified sine wave inverter without any short-term problems.

    I have a few questions.

    1. Will my new (and expensive) CPAP device be ok in the long run with a modified sine wave inverter? or should I invest in a pure sine wave inverter?

    2. Is there any advantage in getting a bigger or better inverter? other than it being able to handle bigger appliances/devices.

    3. The 350w Pro User modified sine wave inverter is very noisy! Are all inverters noisy? Do all inverters run their fan continuously? Any recommendations?

    4. Will I be able to run this device of a 24v battery system? (If I can get the right plug)

    5. How many watts is 2.5a at 12v?

    Any advice will be appreciated, thanks!
    Jeep Grand Cherokee 2002 4.7 V8

  2. #2
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    Default Re: CPAP and Inverter advice needed

    Watts = amps x volts - just remember the battery voltage is not 12v - rather work on 12.6 to about 14.7 when engine is running.

    Instead of an inverter, you could try a dc dc converter like https://www.robotics.org.za/300W-20A?search=Dc%20dc it has a constant voltage setting and a constant current setting. Check your specs on your current charger and then set the dc dc power supply to the same specs - 24v 2.5A. I use the older version without the cc and cv for charging a laptop - gets hot for a while then settles to warm then cool.

    In my opinion inverters draw too much power and as you said it is noisy.

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  4. #3
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    Default Re: CPAP and Inverter advice needed

    Quote Originally Posted by HobieDave View Post
    Watts = amps x volts - just remember the battery voltage is not 12v - rather work on 12.6 to about 14.7 when engine is running.

    Instead of an inverter, you could try a dc dc converter like https://www.robotics.org.za/300W-20A?search=Dc%20dc it has a constant voltage setting and a constant current setting. Check your specs on your current charger and then set the dc dc power supply to the same specs - 24v 2.5A. I use the older version without the cc and cv for charging a laptop - gets hot for a while then settles to warm then cool.

    In my opinion inverters draw too much power and as you said it is noisy.
    Can I use 12v? Will the converter push it up to 24v?

    So basically I would connect the dc dc converter to a battery (12 or 24v?), adjust it to 24v 2.5a output (how) and connect to my device?
    Jeep Grand Cherokee 2002 4.7 V8

  5. #4
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    Default Re: CPAP and Inverter advice needed

    There are built in potentiometers on the board which you can adjust for the maximum voltage and current. I usually hook up a multimeter to check the output voltage. As the battery goes flat or is on charge the output voltage stays the same.

    You can use 12v as the input voltage - that side of things is normally automatic, the unit auto adjusts. The only settings is your output voltage and amperage, and you can set the cut off voltage in case the battery gets too flat. There are built in potentiometers on the board which you can adjust for the maximum voltage and current. I usually hook up a multimeter to check the output voltage. As the battery goes flat or is on charge the output voltage stays the same. I normally adjust the potentiometers and then use nail polish on the screws on the potentiometers to lock the settings.

    Should have mentioned in my first reply that you will need a case / housing to mount the unit in.
    Last edited by HobieDave; 2018/07/01 at 08:15 PM. Reason: Paste error

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  7. #5
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    Default Re: CPAP and Inverter advice needed

    Quote Originally Posted by HobieDave View Post
    Watts = amps x volts - just remember the battery voltage is not 12v - rather work on 12.6 to about 14.7 when engine is running.

    Instead of an inverter, you could try a dc dc converter like https://www.robotics.org.za/300W-20A?search=Dc%20dc it has a constant voltage setting and a constant current setting. Check your specs on your current charger and then set the dc dc power supply to the same specs - 24v 2.5A. I use the older version without the cc and cv for charging a laptop - gets hot for a while then settles to warm then cool.

    In my opinion inverters draw too much power and as you said it is noisy.
    That unit can’t do 12-24V conversion. It is a buck converter, not a boost converter.

    Also, setting the current limit to the appliances spec is just plain a BIG no no.
    Cheers

    ZS5KAD Yeasu Ft-897D
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    The nice thing about going the extra mile - the road is never congested.

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  9. #6
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    Default Re: CPAP and Inverter advice needed

    Fluffy are their specs wrong.

  10. #7
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    Default Re: CPAP and Inverter advice needed

    Quote Originally Posted by Fluffy View Post
    That unit can’t do 12-24V conversion. It is a buck converter, not a boost converter.

    Also, setting the current limit to the appliances spec is just plain a BIG no no.
    Is it better/safer to use an inverter? Maybe I should just try and get a quieter inverter?

    How about using a small UPS? I use 5 in my house. (a 2kva is connected to my CPAP for protection and power failures)

    Once you silence the alarm most of them are quiet. Can I open one up and connect it to one of my 105 DC batteries?
    Jeep Grand Cherokee 2002 4.7 V8

  11. #8
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    Default Re: CPAP and Inverter advice needed

    Quote Originally Posted by HobieDave View Post
    Fluffy are their specs wrong.
    The specs are correct, but the clue is in the word buck.

    Although they spec a range of input voltages and a range of output voltages, what they don’t specify, but what “buck” means, is that the output voltage must be lower, or perhaps nearly equal to the input voltage.

    So this unit will work fine for 24 - 12, but not 12 - 24. To do that you need a “boost” converter, which is typically more complex and expensive.
    Cheers

    ZS5KAD Yeasu Ft-897D
    3 V8's
    A V6 and an inline 4
    The nice thing about going the extra mile - the road is never congested.

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  13. #9
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    Default Re: CPAP and Inverter advice needed

    The cooling fan in an inverter runs as long as it is switched on.
    *
    When you are dead, you don't know that you are dead. It is difficult only for the others.

    It is the same when you are stupid.

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  15. #10
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    Default Re: CPAP and Inverter advice needed

    Quote Originally Posted by Poen View Post
    The cooling fan in an inverter runs as long as it is switched on.
    I am sure that some will be quieter than others?

    That's also one of the reasons I was thinking of connecting a DC battery to a UPS as most of the small ones don't have a fan. The build in charger won't be up to the task of quickly recharging the battery but a separate charger can take care of this.
    Jeep Grand Cherokee 2002 4.7 V8

  16. #11
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    Default Re: CPAP and Inverter advice needed

    Back to my original questions



    1. Will the CPAP device be ok in the long run with a modified sine wave inverter? or should I invest in a pure sine wave inverter?


    2. Is there any advantage in getting a bigger or more expensive inverter? (other than it being able to handle bigger appliances/devices.) Are they more efficient or less noisy?

    3. Does anybody own an inverter that is quiet and doesn't sound like it's about to take off!




    Any advice will be appreciated, thanks!
    Jeep Grand Cherokee 2002 4.7 V8

  17. #12
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    Default Re: CPAP and Inverter advice needed

    a Reply from Eggie on another thread helped me solve my problem, thanks Eggie.

    "you can get a fairly decent inverter from Hawkins, a locally manufactured product with a good reputation. They are totally quiet (no fan).
    http://digisec.co.za/product/cpi-120...ied-sine-wave/"
    Last edited by DC Polokwane; 2018/07/05 at 11:59 AM.
    Jeep Grand Cherokee 2002 4.7 V8

  18. #13
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    Default Re: CPAP and Inverter advice needed

    This little device from Communica MIGHT be able to help you provide a steady 24V DC, but it is only recommended for the (electronically) adventurous. The specs are lacking a bit and it is not clear if it will be able to supply 2,5A @ 24V with a 12V input.


    If it is viable, it would be a very cheap and easy way to power a 24V CPAP device.


    http://www.communica.co.za/Catalog/Details/P4138706545
    Eggie.

    What this country needs more and more, are more unemployed politicians.
    - apology to Edward Langley.

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  20. #14
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    Default Re: CPAP and Inverter advice needed

    Thanks for the advice Eggie but for now I will stick to the KISS rule and I have ordered the Hawkins inverter

    If there is one thing that I have learned in life then it is to stay away from things you don't know especialy when expencive electronic devices are involved and you are in the bush.
    Jeep Grand Cherokee 2002 4.7 V8

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