Sleep Apnoea

[webntweb]

I use a Resmed Airsense 10 apap for sleep apnoea. The manufacturer states the power consumption as 22 watt hour which I presume is a rating at 230 volts.

I would be grateful if somebody could explain to me what that would mean in relation to our 12 volt batteries.

The apap is 24 volt with a 240 volt power supply so I have to use it through our inverter (which is quite an old 1600 watt model and seems to draw a minimum of 400 watts no matter what is plugged in to it). We have two dedicated 110 amp inverter batteries which are usually fully charged by the end of the day.

I normally use the machine for up to 8 hours a night.

Obviously if I can find a mooring with electric hook-up the only problem I have then is knowing how much money to put on the post.

Roy 

 

[woodwose]

If your device is 22W then it will draw just under 2amps from your 12 batteries. If they are 110Ah they will power it for 55 hours in theory. In practice, you will only get half of that and there will be losses in the inverter, but you should get 24 hours easily.

Hope this helps

Nigel

[Timbo]

Argh Roy! Two days too late...I gave my Dad's Devilbis Sleepcube away on Monday!  Dad was having problems when we were on the boat and the local hospital with help from the RN Benevolent guys sourced a model to run on an inverter. I know nothing about electrical appliances...but...they put some gizmo inside the machine so that it worked better with the inverter. It wasn't cheap though at £250.

Those that knew Uncle Albert will be aware that after spending £250, getting the changes made to the machine, he never put the mask on his face but rather wore it on top of his head like a party hat! 

[Guest ExMemberKingFisher]

Whilst Woodwose is correct to a degree, in relation to your statement that the invertor draws 400 watts regardless, this would mean a draw of 33.3 amps per hour which is very high. If that figure is indeed correct then 2 x 110Ah batteries drained to 50% depth of discharge would give you around 3.3 hours before the batteries were effectively as drained as you would want to go. 400 watts draw by the invertor no matter what is plugged in to it does seem excessive!!

[Maxwellian]

I run mine on a special battery when on the boat, charging it up on the car socket during the day when the boat is on the go. Has worked well for the last two years, taking it again for two weeks this year. You can also charge it during stops ashore in pubs etc.

[woodwose]

I just assumed the bit about the inverter consuming 400W all the time is incorrect. If that was true then it would draw about 34A all the time from the battery and it would be permanently flat. If the inverter is actually doing that, then you urgently need a new one. I would consider any device drawing high current like that to be a serious fire risk.

A Scouting friend of mine has one of those machines and takes it to camp with him. He powers it from a lithium ion battery which needs charging every few days.

Nigel

[webntweb]

Thanks all for your prompt answers.

Timbo. My previous Resmed cpap was 12 volts 35 watts and immediately tripped out a brand new 300 watt pure sine wave inverter. There must be something in what you say about cpaps possibly needing updating to work with an inverter. Can't go down that road as it is a NHS machine and it would be my responsibility if an update damaged it; the machine would cost nearly £1,000 to replace.

Woodwose and Kingfishers Time. Our original inverter (fitted by Broom's 20 years ago) packed up last year. Our chairman managed to source the same model which had never been used as it was sat in somebody's house for years waiting to be fitted to an abandoned narrowboat project. When Broom's measured the output of the old one it did seem to draw 400 watts minimum, and the new one seems to be the same. Broom's seem confident that because it isn't in continual use (we switch it off when not being used) that the wiring is of sufficient gauge to be safe. Both of your comments now make me wary of trying to use the inverter overnight.

Maxwellian. My Resmed apap is 24 volts and the guarantee is invalid if I use any other rechargeable battery pack other than their own, which unfortunately they want £400 for.

I will just have to beg other users to share their electric post - I would be happy to refund their £1 and double it up with another card. We have a couple of different splitters onboard.

Roy

[JamesLV]

Being my lovely girlfriend suffers, I wish this was a problem I had to look for a solution for, however she refuses to use a CPAP machine, and as such when we're up in October, any of you on the broads (North or South) will be able to hear her 'sleeping' 

[TheQ]

You might be better getting a 12V to 24 V step up converter, to drive your unit.

[Guest ExMemberKingFisher]

7 hours ago, webntweb said:

Thanks all for your prompt answers.

Timbo. My previous Resmed cpap was 12 volts 35 watts and immediately tripped out a brand new 300 watt pure sine wave inverter. There must be something in what you say about cpaps possibly needing updating to work with an inverter. Can't go down that road as it is a NHS machine and it would be my responsibility if an update damaged it; the machine would cost nearly £1,000 to replace.

Woodwose and Kingfishers Time. Our original inverter (fitted by Broom's 20 years ago) packed up last year. Our chairman managed to source the same model which had never been used as it was sat in somebody's house for years waiting to be fitted to an abandoned narrowboat project. When Broom's measured the output of the old one it did seem to draw 400 watts minimum, and the new one seems to be the same. Broom's seem confident that because it isn't in continual use (we switch it off when not being used) that the wiring is of sufficient gauge to be safe. Both of your comments now make me wary of trying to use the inverter overnight.

Maxwellian. My Resmed apap is 24 volts and the guarantee is invalid if I use any other rechargeable battery pack other than their own, which unfortunately they want £400 for.

I will just have to beg other users to share their electric post - I would be happy to refund their £1 and double it up with another card. We have a couple of different splitters onboard.

Roy

Roy,

A couple of points, firstly your old invertor is probably of an age where it doesn't cut out at low voltage, so if inadvertently left on it could do permanent damage to your batteries. I would think about getting the syndicate to update it for a modern efficient type. I use the Sterling 600W on my boat to power the TV and for charging the laptop etc. Because it is so efficient I tend to leave it on the whole time I'm onboard and moored up. Never seen any significant battery drain. It is also connected to 2 x 110Ah batteries.

Secondly I'm really surprised your previous cpap tripped out a 300 watt invertor, especially if it was a pure sine wave unit. It's possible that the start up current drawn by the unit momentarily exceeded the rating of the invertor. It could be worth trying the Sterling 600W or trying to persuade the syndicate to replace the 1600W one with a new one from Sterling. You should be able to get the 1600 for around the £330 mark.

https://www.beaconsandlightbars.co.uk/Sterling-Pro-Sine-wave-Inverter/

 

[Vaughan]

I assume you will be using this in your cabin, which may be a long way from the batteries, so you may suffer volt drop in the wiring.

I have fitted a lot of devices in hire boats - when customers think to ask in advance - and I usually fit a separate, temporary wire with a fuse and a cigar lighter socket, connected direct to the domestic batteries.

Shore power is best, of course!

[stumpy]

Kathy uses a Resmed  IP21 (previous machine was a Respironics something or other). Away from shore power it works a treat on a Sterling 1800w pure sine wave inverter. When we had the inverter fitted HW put an extra domestic battery in giving us 3x 110amps. We usually only run on battery for one night at a time with a good run during the day. Had no problems yet, except when we learned you can't just add one new battery to a bank! Hope this helps. 

[Vaughan]

2 hours ago, stumpy said:

Had no problems yet, except when we learned you can't just add one new battery to a bank!

You can, but then you might need a bigger alternator to charge it all up again!

[webntweb]

Thanks everybody for your replies.

I will look into all suggestions. Hadn't thought of TheQ's idea of the 12v to 24v step up converter - will do some research on that one.

Roy