My battery backup setup

[Marthajoy7]

VE7LTD

I still have not seen any reply that data on the unit is valid when using this setup. Even a statement that data was readable by sleepyhead would give me a lot more confidence before hooking up to a rental unit. Both our units are still under medicare rental time period.
Do you believe the setup of yours could be used to power 2 s10 machines at the same time, like I wish to do? I believe you said that you had tested on three different units. 5 amps times 24vdc would be almost 120 watts. A lot stronger than Resmed's converter. Also a whole lot cheaper. I see where your setup can be built for less than $25. Quite a Savings for something stronger power wise.

[BadGoodDeb]

Not sure if the battery size vs Cpap setting chart got quoted or not. It was in this post of this thread. (Yeah, I see it didn't get quoted.)

Assuming a cpap setting of 10, so 12 amp-hours needed for 8 hours of sleep (per chart) --- how many nights (or hours) will my teeny trailer's battery give me? I don't know how to interpret the numbers on it. It's a "Harris" deep cycle battery, 24D140 Professional Plus.

I'm figuring if I have a household power outage, I'll just sleep in my teeny trailer in the garage. But I'd like to know how many hours that'll cover. And whether I can afford to run the fan & light when I'm actually on a trip, and yet want Cpap time on the battery. The trailer already has a battery tender built in for charging, so all I have to buy is ResMed's "DC POWER CONVERTER WITH CORD FOR AIRSENSE™ 10 CPAP & AIRCURVE™ BILEVEL MACHINES" which includes the cigarette lighter plug too.

I couldn't find a direct figure for that battery, but it shows "Craniking Amps" so it is a little tiny bit suspect in my mind, but Batteries+Bulbs shows a replacement for that unit on their website (Duracell Ultra Battery Harris 24D140 Replacement SLI24MDC) that shows it with a deep cycle capacity of 75 AH. Not saying it is what you got, but it may be close/comparable for your planning purposes.

OMMOHY

Thank you!! I sent an email question to the manufacturer, and got an automated reply "we'll get back to you" .... but that was 2 or 3 days ago now and I've heard no more. So your reply may be the only info I'll get. Thank you!

[Marthajoy7]

Assuming a cpap setting of 10, so 12 amp-hours needed for 8 hours of sleep (per chart) --- how many nights (or hours) will my teeny trailer's battery give me? I don't know how to interpret the numbers on it. It's a "Harris" deep cycle battery, 24D140 Professional Plus.

This statement has me confused. 12 ah for 8 hours of sleep. Is that 12 amps for every hour of use? I doubt that. So I take that as 1.5 ah which would equal 12 amps after 8 hours. That statement means that if using 2 12vdc batteries in series with no converter, the current draw would be 0.75 amps per hour. Also make sure the battery you are using is vented yo the outside as lead acid batteries can be bad for your health.


here are the specs for your battery
SPECIFICATIONS:

Harris Battery Part #: 24D140
Volts: 12
BCI Group Size: 24DC
Weight lbs: 45.00
Weight kg: 20.41
Length inches: 10 1/4
Length mm: 260.00
Width inches: 6 13/16
Width mm: 173.00
Height inches: 8 7/8
Height mm: 225.00
Cranking Amps @ 32°F 0°C: 685
Cold Cranking Amps @ 0°F -18°C: 550
Reserve Capacity @ 25 Amps: 140 mins
Core Unit: 1.00

Reserve capacity to me means that it can handle 25 amps for 140 mins. So 24 x 140 / 60 means that battery is about 58 AH. How long that will work depends on interpretation of previous statement. I think AH was used instead of amps. So if that is the case. The battery would almost last 5 nights, but 4 providing nothing else is being used by the battery and that the converter is unplugged when not in use. As even when off so juice will drain drom the battery through the converter.

I hope that helps you.

[BadGoodDeb]

Assuming a cpap setting of 10, so 12 amp-hours needed for 8 hours of sleep (per chart) --- how many nights (or hours) will my teeny trailer's battery give me? I don't know how to interpret the numbers on it. It's a "Harris" deep cycle battery, 24D140 Professional Plus.

This statement has me confused. 12 ah for 8 hours of sleep. Is that 12 amps for every hour of use? I doubt that. So I take that as 1.5 ah which would equal 12 amps after 8 hours. That statement means that if using 2 12vdc batteries in series with no converter, the current draw would be 0.75 amps per hour. Also make sure the battery you are using is vented yo the outside as lead acid batteries can be bad for your health.


here are the specs for your battery
SPECIFICATIONS:

Harris Battery Part #: 24D140
Volts: 12
BCI Group Size: 24DC
Weight lbs: 45.00
Weight kg: 20.41
Length inches: 10 1/4
Length mm: 260.00
Width inches: 6 13/16
Width mm: 173.00
Height inches: 8 7/8
Height mm: 225.00
Cranking Amps @ 32°F 0°C: 685
Cold Cranking Amps @ 0°F -18°C: 550
Reserve Capacity @ 25 Amps: 140 mins
Core Unit: 1.00

Reserve capacity to me means that it can handle 25 amps for 140 mins. So 24 x 140 / 60 means that battery is about 58 AH. How long that will work depends on interpretation of previous statement. I think AH was used instead of amps. So if that is the case. The battery would almost last 5 nights, but 4 providing nothing else is being used by the battery and that the converter is unplugged when not in use. As even when off so juice will drain drom the battery through the converter.

I hope that helps you.

Thanks! And re safety: this is a retail camper. The battery is stored outside, on the tongue. Oh ... you mean I still need to vent the *garage*, if I sleep in it while the whole trailer is in the garage? Good thought. Would a foot or so of garage door opening suffice? It it's winter, I don't really want to get cold!

[ve7ltd]

The data on the SD card is not at all affected. I can pull the card and read it in SleepyHead even after using my backup setup. I don't know why you would be worried that the data being output from the machine would somehow corrupt the machine's data. It does not make any sense to me.

This DC-DC unit I have would be fully capable of feeding two machines. All you would have to do is parallel the power cables from the 24V side.

You would need two 47K resistors - one for each cable. That way they would run independently of each other. I would also use a short wire between the 12V battery and the DC-DC unit. You also should get a Low voltage disconnect switch. There are several on ebay - just search for 12V Low Voltage Disconnect. I think there is a 12V 30A version that would work well for this application.

I am going to buy a 10A disconnect, as my machine rarely pulls more than an amp at 12V from this setup, but my pressures are fairly low (about 6.0-10.0). This is with the humidifier and heated hose in use.

In my trailer I have a pair of 6V 220aH cells (golf cart batteries) wired in series. I recently went on a camping trip and used the machine for 3 nights and didn't even notice the battery voltage drop at all.

I hope this setup (or something similar) works for you. I think I am done explaining it, as it works for me, and posting more about seems too much.

Dave

[surferdude2]

Just a reminder, connecting all conductors in parallel when both have 47k resistors in them will present the machines with 23.5 k (product divided by the sum) effective total resistance and may give you untoward results.

Connectibg power cables ONLY would be ok but I suppose you knew that. Others might get misled, so thought it worth mentioning.

Dude

[ve7ltd]

I think you misread the idea. The 47k is on the sense line. I was saying you need to put a separate resistor in each sense line (she wants to run 3 machines from a single 24v power source).

[Marthajoy7]

Dave,
Thank you for your help. Concerns that damage to my rental Bipap had me very concerned with just a resistor, when resmed puts a converter in every power device they sell. I do not have a schematic for the 2 devices that we use, so I have no idea what is in them. You sound like you are very happy with your setup, and I am still waiting for parts. I need a new soldering station, as I cannot locate my old ones. I use them so infrequently any more. Tremors in my arms and legs can make it difficult to work on electronics any longer. Your work on this has helped me a lot. Within a few days now, all my supplies will arrive. I do not drive myself anywhere any longer. Scared to drive when arms start moving every which way. Again thanks. I hope others find the work helpful as well

[surferdude2]

ve7ltd, Yes, you're right, I didn't read the long history of the thread so I'll duck back in the weed and assume you guys have it covered. I did read enough now to marvel at how much effort you have put into this. It would seem to be a simple problem but that can sometimes be misleading.

Dude

[Marthajoy7]

Actually, What I need to work in a power outage. Two Resmed machines, one an AirSense 10 for her and the other an AirCurve 10 vpap. I also have need of my oxygen concentrator which runs off of 120vac. I have purchased an inverter to run it, but was told not to run the Resmeds off of the inverter as it is not a sine wave output. Some suggested I power it off of a Generator, but as I live in a mobile home park, that will not work. I have no problem running a generator during the day, but no way at night. Therefore, I can use it to recharge batteries as needed during the day. As there are no noise restrictions during the daytime. I hope the inverter will work for the oxygen concentrator, as I have not found anything that says power needs to be pure sine wave. Most of its power requirements also goes to air blowers, as it works by blowing air through chambers with like crystals that pull nitrogen out of the air, then switches to a second chamber while it reverse clears the collected nitrogen out of the machine. Thus it constantly changes between chambers to give me enriched oxygen.
I could talk to my doctor about oxygen tanks, but I consider them a safety hazard. Rather than flammable oxygen around, I prefer machines that can give me oxygen as I need it.
I also have a portable concentrator but that only requires 12vdc ans can charge from the 12v output on the generator, but that cannot be used with my bipap as it is pulsed to only provide oxygen when I breathe in, which it cannot detect when using bipap.