Reliable Battery Power for CPAP machine

Submitted: Monday, Jun 13, 2005 at 10:28
ThreadID: 23816 Views:3718 Replies:8 FollowUps:4
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Morning everyone. I have just returned from 3 fabulous weeks cruising the outback including Dalhousie and Oodnadatta track - great trip but had difficulty with power to run my CPAP machine (used for sleep apnoea). The unit _Affordable_Storage_Drawers.aspx 3 amps at 12 volts and I found that using my dual battery system was not sufficient to run the machine all night, even when we had been driving all day and the system should have been fully charged. The only other power draw on the system was an engel 40 ltr fridge and a versa light. The system used to run it ok but now it runs out of charge very quickly, (leaving me gasping for breath and unable to sleep). My question is this:

Leaving the dual battery system for the fridge and a versa light, how can I set up a solid reliable battery system to ensure I have power to run something like this for an average 8-9 hours per night? I have a camper trailer and thought of placing a battery or batteries in the toolbox connected to an anderson plug. Any suggestions from the wise people of the forum would be greatly appreciated as if I can't fix the problem it will greatly restrict our ability to travel to remote areas.
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Reply By: Lone Wolf - Monday, Jun 13, 2005 at 10:46

Monday, Jun 13, 2005 at 10:46
Something is most definitely wrong!!

I have just returned from a 3 week sojourn, and had no problems whatsoever.

I use a Res Med Auto Spirit, and it _Affordable_Storage_Drawers.aspx around 1.3 amps @ 12 volt running @ 9 bar.

I am assuming you are NOT using the humidifier? That will kill any battery system, as it requires pure sine to begin with. Humidifier is unnecessary whilst camping. There is usually enough residual humidity inside the tent / swag / camper to compensate.

I sometimes sleep for maybe 10 - 11 hours @ night, and I have never had a problem.

Mem mes me if you want to talk further.


AnswerID: 115527

Reply By: Member - Luxoluk - Monday, Jun 13, 2005 at 16:57

Monday, Jun 13, 2005 at 16:57
Are you running your machine from a 240V inverter or is it 12V direct? I use 12V direct to the CPAP, run 39ltr engel, HF radio and versa lights and seem to cope ok. May also need to look at the charging side....big cables all the way!!! Cheers

AnswerID: 115553

Follow Up By: Member - Nissan Gnome - Monday, Jun 13, 2005 at 17:28

Monday, Jun 13, 2005 at 17:28
12volt direct. It would appear I need to look at the battery etc. Thanks
FollowupID: 371207

Reply By: PsFish - Monday, Jun 13, 2005 at 17:02

Monday, Jun 13, 2005 at 17:02
On a standard 50amp battery run a 40 ltr Engel, lights and Res Med Auto Spirit machine I will normally get 24hrs out the battery that is fitted to my Heaslip Tray on. I changed to a 100amp battery in the camper which allows for 48hrs base camping without having to reconnect the truck to the camper which has another 2 x 70amp batteries. I was suprised when I could only get 24hrs out of the smaller battery before the alarm of the inverter went off.

I'm off to the corner country early next month for two weeks so I will be interested to see how my gear stands up to the power draw.
AnswerID: 115554

Reply By: Member - Jimbo (VIC) - Monday, Jun 13, 2005 at 17:08

Monday, Jun 13, 2005 at 17:08

If it used to work OK and now doesn't, I'm guessing your aux batt is wellington booted, or the charging system. I'd get it looked over by a battery expert.

Try Chris at Battery World, Wantirna. Honest bloke, fair prices.


AnswerID: 115555

Follow Up By: Member - Nissan Gnome - Monday, Jun 13, 2005 at 17:30

Monday, Jun 13, 2005 at 17:30
Thanks Jimbo, will give him a call. There is nothing more soul destroying than having to be awake in the middle of the night listening to other people snoring!!!

PS When are you next going bush? Give me a yell.

FollowupID: 371208

Reply By: drivesafe - Monday, Jun 13, 2005 at 21:19

Monday, Jun 13, 2005 at 21:19
Hi Nissan Gnome, Jimbo’s suggestion is the safe way to go but being in the situation that you are, it would also pay you to carry a multi meter with you so you can get an idea of what is happening around your vehicle.

The problem sound like you have a battery operating on it’s last legs but you may need to have your alternator overhauled, or maybe it’s simply a bad or loose connection somewhere and any number of other possibilities.

A multi meter will help track down the problem and may save you some money in the process.

AnswerID: 115599

Reply By: tonysmc - Monday, Jun 13, 2005 at 21:25

Monday, Jun 13, 2005 at 21:25
Hi, I know I will start some arguements here, but are you using a deep cycle battery for your aux? If you are I would change to a starter for the Aux. The reason I say this is because you said it did work ok, but now it doesn't. The problem I have found is the (wet cell) deep cycle only accepts a charge slowly and will not get a full charge via driving all day. So leaving home your battery is full, but each day it doesn't quite charge to what it was the night before. By 3 weeks away and its not working much at all because it needs a long slow charge from a 240 volt supply. Starter batteries recharge quickly. I know you can get AGM batteries, but for the cost a good starter will do the job fine. My aux starter batteries last a bit over 4 years. If you connect everything through a low battery cut out switch you'll never have a problem with a starter as a second battery.
That is MHO and I know many will disagree, but I hope it helps
AnswerID: 115600

Follow Up By: Member - JohnR (Vic)&Moses - Monday, Jun 13, 2005 at 22:27

Monday, Jun 13, 2005 at 22:27
tony, perhaps you haven't got a big enough lead to and from your deep cycle. The starter batteries don't take too kindly to deep discharging and decay quickly if you do so. If you have big enough ones though they can be ok. My ute one proves that actually as it has been flat twice and is just over two years old, it won't last beyond the winter if it goes that long.
FollowupID: 371242

Follow Up By: tonysmc - Tuesday, Jun 14, 2005 at 14:41

Tuesday, Jun 14, 2005 at 14:41
If you read what I said about a low voltage cut out you will find you don't have a deep discharge, that is the point of them. I have tried large leads and it made no difference.
FollowupID: 371320

Reply By: GO_OFFROAD - Monday, Jun 13, 2005 at 22:55

Monday, Jun 13, 2005 at 22:55
I also use a cpap running from a 300w sine wave invertor, and it _Affordable_Storage_Drawers.aspx just over 1 amp, and I dont use the humidifier, I find I can just get 2 nights camping in medium weather, with a 1000cca battery and the n70zz starter battery, with them linked.

I carry a bushranger 4000 also, and have had to get up a couple of nights on the 2nd night camping to connect it to the aux battery when i ran 2 x n70zz's before getting the bigger battery, and had no trouble since. The bushranger plugged into the aux acc plug then charges like a 3rd battery while driving, and disconnects when the acc are turned off.

I have also had to jump start the car with the bushranger 4000 a couple of times after 2 night camping, when the batteries have been joined as one.

My new truck wil have n70zz start battery, and 2 x n70zz's linked as one battery as the aux.

The cpap has been easy, after afew years ago, before my wifes kidney transplant, when we had a 1500w sine wave invertor and 5 n70zz batteries in the car to run the wifes dialysis machine for 10 hrs each night, and would then run the gennie in the morn with a battery charger to top them all up again before driving.

With 5 batteries, I would have to run the car for about 20 minutes when she started the machine, or the 5 batteries wouldnt last the full 10 hours without the voltage dropping low enough for the low volt alarm to go off.
AnswerID: 115619

Reply By: itisi - Tuesday, Jun 14, 2005 at 02:09

Tuesday, Jun 14, 2005 at 02:09
Would definitely check out battery/charging system.
Tuther half needs a CPAP machine and the first one she had was a Fischer n Paykel unit (can't remember model) drawing around 180 watts on 240 volts so free camping posed some problems. (thats about 15 amps on 12 volts). Had to use a pure sine wave inverter. We did manage a day here and there but not as often as we would have liked!!

She now has a Puritan GoodKnight 420 (12v) CPAP, Devillbis passover humidifier and 12v heated tube.

This combo _Affordable_Storage_Drawers.aspx only 2 -3 amps. The puritan passover humidifier wasn't available at the time we purchased our gear hence the Devillbis.

With 2 x 80 amp batteries in the van running lights, CPAP, Vitrifrigo 12v fridge and car fridge we are now capable of spending several days away at a time.

AnswerID: 115637

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