Battery for CPAP

[cubes123]

I've had a look but not found a definitive answer.

I was thinking about getting a 110Ah leisure battery as a backup in case of a power-failure. I've seen the "super cpap battery pack" here but £299 seems a bit steep...

Just wanted to know if, with the right cable, it's safe to do this?

I'm talking about something like this - http://www.tayna.co.uk/Numax-CXV31MF-P3694.html

Thanks!

[James @ Intus]

Safe, yes. Handy to lug with you...? No!

Plenty of people use a car/caravan/boat battery for their CPAP and plenty of people use that Super CPAP Battery Pack for their CPAP. It's a trade-off between portability and budget indeed.

[Fredxx]

I think I can claim to have an independent view on this having tried both a "leisure" caravan battery and the Super CPAP battery.

Several years ago I bought a leisure battery from a camping and caravanning shop, settling for an 85Ah one as being a reasonable capacity whilst not being too much to lug around when camping. To the battery I had an adapter that connected to the terminals with crocodile clips giving a car cigarette lighter connector, into which I could plug an invertor, into which in turn I plugged the CPAP machine. The down sides to this lot were:

• The battery is heavy, so you don't want to lug it far from the car!
• The battery fully charged would only power my old Fischer and Paykel machine for 6-7 hours at 16cm with the humidifier off
• once the battery was about 80% used, the power level dropped and consequently the pressure supplied to me by the machine
• The batteries take a while (and of course a power supply) to recharge
• Don't even THINK of trying to take the battery anywhere with you on a plane!

May 2010 we were off on a trip on a boat on the Norfolk Broads for a week, so power for my CPAP was an issue. Combined with this, I wanted to get a second CPAP machine as work has me travelling away a lot, and constantly dismantling and reassembling the machine was becoming a pain! A little research (with a little help and advice too, thanks James), meant I invested in a DeVilbiss Sleepcube CPAP machine (this will run off a 12v supply with no inverter, and much more efficiently than the F&P machine) and the Super CPAP battery.

• A single charge of the battery gave me almost 3 full nights sleep (not a fair comparison really, as the machine is more efficient)
• The power, and so the pressure, stayed pretty constant right up until the last few minutes of battery life
• A couple of hours a day plugged into the boat when the engine was running recharged the battery fully
• Not only have I been able to take the battery abroad with me on a plane, I was even able to use it to power my CPAP when we were flying (although technically the battery is a higher capacity than they are supposed to allow for cabin use)

For me, the SleepCube and CPAP battery were a worthwhile purchase, and I am in the fortunate position that I could afford the cost of over £500 to do it. Using your existing machine and getting an £85 leisure battery, charger, inverter, leads etc. is a cheaper way to do it and works perfectly fine, but be aware of the limitations

[cubes123]

Thanks for the info. It's really as a backup in the home, hence the reluctance to spend £300, but then, when it's your health at stake...

I've on a remstar M101 with no humidifier at 13cm. I've got the adapter for a car lighter socket already.

More thinking required I guess.

[Fredxx]

If all you are going to use it as is a backup battery under the bed, definitely go for the caravan battery, and as it won't be moving far, go for a big one; it is a lot cheaper and portability isn't an option.

Make sure you get a "leisure" battery though, not a car battery. Car batteries are designed to operate sat at full charge normally, and not to do "drain-charge-drain-charge" cycles, these drastically reduce the life of the battery and you start to see effects on the capacity after only 20-30 cycles.

Leisure batteries are designed to go through the drain-charge cycles after all, that is what you want to do in a caravan or boat! You should then get 100 - 200 cycles before you start seeing effects.

For me, the portability was an issue, as was the ability to take it abroad with me.

[symmit]

If it's just for power backup at home why not buy a small but decent UPS?

<<day job mode on>>

We sell APC. To give you an idea, with a 50W load an APCBR900GI has a runtime estimate of 2hr 4 min for an RRP of about £140. The output is on IEC power leads so you'll need to make up an adaptor but I'll normally hang a 4 or 6 way strip off one to power all the small bits that don't use IEC connectors. That should see you through most blips and outages in the night, and also protect your equipment from spikes and surges and brownouts. I'd have to check that the power alarm can be turned off though otherwise it'll wake you up by bleeping loudly when the power fails - probably counter productive

Output is of course mains, so no problems with any machine with a switch mode supply (if it's auto voltage 110-240 then it'll be fine) - older stuff with traditional wound transformers can be fussy with the output from a UPS.

I've got my media/mail server, router and cordless phone base on one here (on an SUA1000I) and it runs for about 90 mins if the power fails, never even thought about the CPAP but now it's come up I'll get it on one - I've got a spare SUA1500I which should run it for 5 hrs

[Fredxx]

I did think of UPS when I was looking into it (I work in computers and technology too), but it wasn't a\z good solution for what I needed:

It is again an expensive option (I believe the SUA1500I you mentioned retails about £300 plus VAT)

Portability is a problem, as you are now lugging round all the inverter and control systems in the box

The batteries in the UPS are again not designed for excessive drain-charge cycles; they are intended to remain topped up and ready for occasional events, so only do a relatively few cycles before the capacity declines.

UPS tends to supply mains voltage, so to run the CPAP machine you are using an inverter to take the 12V DC supply up to 240V AC, then the CPAP machine will take it back down to 12V DC (most CPAP fans and components run at 12, 14 or 16V DC); all that power conversion just uses the battery capacity, so if the machine has a 12V power connector it is better to connect a battery direct through that.

Having said all that, the ability to connect the CPAP machine to the mains through a UPS, so that if the power fails at night the switch to battery power is all handled and you don't notice, is an intriguing though. I guess the value depends on how reliable the mains power is!

For reference on the APCBR900GI, the Fischer and Paykel machine I have takes about 70W with the humidifier off, so that wouldn't even supply a full (90-ish minute) cycle of sleep for my set-up, although that 70W measure was from battery to inverter, not inverter to machine...

[Tigers Fan]

Is this a rural thing?

I remember blackouts from decades ago when I was a boy and living in the country. I can't remember ever having a blackout since I moved back to UK and lived in the city - a tad over two decades ago.

I'm intrigued by your concern over a back-up power source.

TF

[James @ Intus]

We get calls regularly, mainly people at the "end of the grid", out in the sticks, who get monthly blackouts. Here in the office, we get them once a year, about 6 hours, always on a weekday when it's busy!

Some machines, like the SleepCube for example, can switch automatically between DC and AC so a power cut will be seemless for you, aside from your alarm clock not waking you up!

An uninterruptable power supply will often cover regular blackouts that generally last just a few hours so indeed, for pure backup, that's also a good option.

[Fredxx]

When I first got the battery and inverter back about 7-8 years ago I did it because we were having regular power cuts; used to happen a coup[le of times a month and be off for usually just a couple of hours. Of course, within a couple of months of buying the battery, Western Power decided to replace the sub-station...power has only gone out 3 more times since then!

[cubes123]

I remember blackouts from decades ago when I was a boy and living in the country. I can't remember ever having a blackout since I moved back to UK and lived in the city - a tad over two decades ago.

I'm intrigued by your concern over a back-up power source.

TF

It's a just in case sort of thing. Relatively cheap to do considering the benefit.

Or maybe I just read websites such as peakoil.com and powerswitch.org.uk to frequently...