Medical Device Battery Requirements

[cubbieco]

Hey my first post. Been lurking a while and I'm in the planning stages. I'd like to start building this fall but we'll see.

I'm asking a question that I think is fairly obvious but this is rather important so I'll ask anyway. http://www.resmed.com/uk/assets/documen ... lo_eng.pdf - I use a BiPAP for sleeping (similar to a CPAP but a step up) and according to that guide if I get their DC to DC converter I should use 14 amp hours at 12 volts running that machine per night (with their built in 50% safety margin). Now I'm probably going to go the battery overkill route anyway, still if I've been reading this right assuming volts are equal (12v vs 12v) this 14 amp hours the machine uses should convert directly to battery capacity. So in theory a 100ah battery with 50ah "usable" would run this machine for between 3 and 4 nights (assuming a fully charged battery, no lights, no other loss.) Is this correct?

So if I want to do led strip lights with possible multicolored accent lights and run a small tv/whatever I should plan on 200ah worth of battery power (100ah usable) to last two nights without recharging and for anything longer plan on charging the battery somehow. If I wanted to stretch it for three nights I'd probably need a solar system to replenish at least some of the battery power I used. Are these fair statements?

I know your mileage may vary, everybody has opinions, etc but from what I've read you guys are friendly and (more or less) knowledgeable.

Thanks

[Catherine+twins]

Hi, Cubbieco

I don't have the answer, but I'm glad you are asking this. I have a friend who has recently been prescribed a CPAP, and she is planning only for the minimal needs, not for additional lights or anything. I think she will find the other creature comforts creeping up on her, and will regret not planning for some lights, etc.

Damn, getting old takes planning ahead! We don't plan to quit camping, though!

Catherine

[working on it]

Part of the "specifications" given me by my wife, if she was "ever going to use the trailer", was a place for her BIPAP machine (I had called it CPAP for years, but was recently corrected on this matter).

BIPAP basket in cabin.JPG (150.6 KiB) Viewed 2515 times

I constructed the trailer with 2 power modes: an Optima Yellowtop battery (12vdc) to power 12v LED lights, computer case-fan-ventilators and car stereo, and a 12vdc-to-110vac 410watt inverter (to use in case all 110vac sources failed), and either park-sourced power or trailer-mounted 2500watt generator to power the 110vac LED lighting, A/C unit, heater, main ventilator fan, and BIPAP . If the park power or generator failed, then the battery alone would (thru the inverter) power the BIPAP and minimal 12vdc LED lighting, plus the computer fans for ventilation, thru a coupla nights in my worst case thinking. And, if worse became worst, all my vehicles have 400watt inverters, that could also power her BIPAP machine. She could sleep a night or two without the lights, fans, A/C, heat, or stereo, but I'd rather have her use the BIPAP in any case.

[rainjer]

I have a CPAP machine and I use a 115ah deep cycle battery in my teardrop. If I don't run my lights much I can get 4-5 night (7-8 hours) of of one charging.

Jeremy

[48Rob]

So in theory a 100ah battery with 50ah "usable" would run this machine for between 3 and 4 nights (assuming a fully charged battery, no lights, no other loss.) Is this correct?

So if I want to do led strip lights with possible multicolored accent lights and run a small tv/whatever I should plan on 200ah worth of battery power (100ah usable) to last two nights without recharging and for anything longer plan on charging the battery somehow. If I wanted to stretch it for three nights I'd probably need a solar system to replenish at least some of the battery power I used. Are these fair statements?

Yes, your assumptions and math are correct...unless their DC-to-DC converter uses/consumes power to operate.
I'm not understanding the need for a DC TO DC converter if both are 12 volts.
If the machine uses a different voltage, then the converter makes sense.

Rob

[Glenn Butcher]

My new machine has a 12v input.

I think you'll get more hours of operation running it directly on 12v if you can, vice inverting up to 110v and plugging the 12v transformer into that.

[cubbieco]

This machine is 24 volts. :-( I already have an inverter I could use but I figure if I'm trying to stretch a battery I need to stick with efficiency on this one even though it means something else to buy. Thanks for the info.

[tony.latham]

This machine is 24 volts. :-( I already have an inverter I could use but I figure if I'm trying to stretch a battery I need to stick with efficiency on this one even though it means something else to buy. Thanks for the info.

I've been building a teardrop for my sister. She too is on a Resmed "iron lung," so I've been working the build around her CPAP needs. She wanted a folding shelf for her device. Here's a picture of it. The folding brackets are not hard to find. I bought these from Amazon.


I suggested she put the CPAP on the shelf with the 12V outlets but she insisted on the folding shelf.

Initially, she was planning to run her Resmed CPAP using the 120v inverter cord that came with the device plugged into a 120v/12v inverter. I finally convinced her that running her 24v to 120v inverter cord plugged into another 120v to 12v inverter (running off the 12v battery) was a bit on the insanely inefficient side. She now has the 12v to 24v converter cord that Resmed sells and I'm sure it'll work just fine.

I also installed a shore power plug to enable her to run the CPAP seperate from the battery when 120V was available. I bought this $14 port plug from Amazon and it works great for what her needs may be: http://www.amazon.com/gp/product/B009AN ... UTF8&psc=1

Tony

p.s. If I've got my ducks in a row, inverters change the current from DC to AC and converters (in this case) from 12v DC to 24v DC.