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Oxygen machine back up power

Okiefrog

Feb 24, 2014
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Help,
My wife is on oxygen 24/7 and uses a big concentrator during the day. The other night the power went out and she used up both batteries on her portable unit. Inadvertently I was called home from work to move her to power. We live in a rural area and temporary power outages are almost normal.
I came up with this bright idea to build a back up out of a small car battery and a cigarette style power point with a float charger. My original design has 2 sockets for power (also charge the call phone) with a 30Amp inline fuse. I had it setup to physically connect the float charger kind of like my battery maintainers were connected in my boat for the trolling motor batteries. We thought it was a good idea.
So I wired a power socket direct to my lawn mower battery as a prototype to test how long the battery would run the machine to gauge the battery size I would need. Battery is in it's third or fourth season but was fully charged by a automotive battery charger and is kept indoors during the winter.
When connected it lasted 22 minutes and blew the fuse in the power supply, I replaced the fuse and it immediately started to fail (slow blow fuse). After the fuse failed I connected a analog automotive battery analyzer to the battery and it read a good 12v
I am really perplexed on why this did not work, the idea is solid and even the small lawn mower battery should have powered it at least 8-12 hours in my estimate. When connected the charger back to it it read 9.4 volts and charging started at 6%.
My 2 possibilities are the battery has a dead cell shorted across the plates and died way too soon or the output amperage was way too high connected directly to the battery.
Now the details- the power supply has information
Input 11-16vDC,7-5A
Output is 18VDC/3.3A
The internal fuse is 8A250V slow blow.
3 questions from the people that may know the answers;
1- Is this a feasible project that will eventually work well, or a colossal waste of time and money.?
2 - Would you suspect the battery to be bad and be the problem with the results I have.?
3 - Or is the output amperage if the direct battery connection too much for the power supply and can it be reduced at a nominal amount if work.?
Normally the internal battery in the portable lasts about an hour, how long should a regular 12v lawn mower battery last if it would work and if used a small car battery (500CCA) would it be better and how much better.? 8-12 hours is plenty for a back up.
 

Arouse1973

Adam
Dec 18, 2013
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What is the Amp hour rating of the lawn mower battery. This is a feasible project and it sounds like the battery dropped below 11V and the step up regulator drew too much current trying to produce 18V and the cycle continued until the fuse blew.
Adam
 

mursal

Dec 13, 2013
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Dec 13, 2013
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Its probably in your text, but sorry I cant find what the circuit needs, is it a 12Volt circuit you are driving? And how much current flow does it need?
 

duke37

Jan 9, 2011
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Are you connecting the mower battery to the internal battery?
Are they the same voltage?
 

Okiefrog

Feb 24, 2014
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1- I don't know the amp hour rating of the battery and I'm not sure how to determine it - the battery is marked type U1
2- the regular connection I'm using is a car adaptor for the oxygen machine
3 - the car adaptor plugs into the same connection on the side as the home charger/AC adaptor. in the past we have used the AC in the car with an inverter because the original car adaptor started eating fuses quite regular, and Wally World don't stock that fuse
 

Okiefrog

Feb 24, 2014
9
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What is the Amp hour rating of the lawn mower battery. This is a feasible project and it sounds like the battery dropped below 11V and the step up regulator drew too much current trying to produce 18V and the cycle continued until the fuse blew.
Adam

And keep in mind this battery is 3 years old this spring and a small liquid cell battery that age may be fused internally, or starting to go bad
 

Okiefrog

Feb 24, 2014
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Feb 24, 2014
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And if I' m shopping deep cycle batteries what amp hour rating am I looking for?
I'm seeing some 35AH batteries that are not listed as deep cycle
 

mursal

Dec 13, 2013
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So if you are using the car adapter into the oxygen machine, just connect a 12volt car battery (or deep cycle if you want) to the input. As you know be aware of polarity, the center pin will be positive (+).

You will have to measure the current flow into the machine with everything running, using an amp meter on one of the input wires. This will tell you the size of the charger required to keep the machine running while you have mains electricity supply, if required. It will also allow you to size (Ampere Hour capacity) the battery required to run the machine, when you have no mains supply.
The data sheet for the machine will also tell you the maximum current needed to run the device.

Sorry, I don't know why the fuse keeps blowing
 
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Okiefrog

Feb 24, 2014
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What is the Amp hour rating of the lawn mower battery. This is a feasible project and it sounds like the battery dropped below 11V and the step up regulator drew too much current trying to produce 18V and the cycle continued until the fuse blew.
Adam

OK I narrowed it down to the battery type is incorrect-it needs a deep cycle battery. Online I found several wheelchair type batteries but I would respectfully ask someone help me determine the right battery CCA-AH etc....

Also the battery charger I was going to use is a plain jane Centec float charger from harbor freight and I seen a 3 stage float charger at one of the battery websites for about the same price, would they have the same result and can it be manually connected all the time if it was not plugged in while being used for discharge.
And about the below 12V draw blowing the fuse hoe do I prevent that from happening when the correct battery is being used.
I looked online for the data sheet on the machine andhere is no info on it even in the user manual, it is an Invacare XPO100 and the DC adaptor is model XPO140.
If you would prefer Email talking about this my address is [email protected].
 

flippineck

Sep 8, 2013
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From the manual for "XPO2 Portable Concentrator" http://www.invacare.com/doc_files/1148112.pdf:

AC Power Supply: 100-240 VAC 50/60 Hertz
DC Power Supply: 11-16 VDC

Rated current input:
1.0 amps at 120 VAC
3.3 amps at 18 VDC

this is for XPO100B

it seems to say the step-up converter takes 7Amps at the lower voltage end (11v) falling to 5A at the 16V end.. so let's work with 7A to be safe

... & you want to run it for 12 hours = 84AH

let's assume you probably need a margin for inefficiency guesswork etc, say 100AH

yes a deep cycle battery would be better

so something like this 100 AH / Amp Hour model http://www.ebay.co.uk/itm/12V-100AH...ervan_Caravan_Accessories&hash=item2c66f2a7db

i'm in the uk so you'd obviously need to ebay something closer

not sure why the fuse blew though, Arouse1973 might be right there..
 
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Okiefrog

Feb 24, 2014
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From the manual for "XPO2 Portable Concentrator":

AC Power Supply: 100-240 VAC 50/60 Hertz
DC Power Supply: 11-16 VDC

Rated current input:
1.0 amps at 120 VAC
3.3 amps at 18 VDC


OK so what AH battery would be best to run 8-12 hours and what about the discharge below 12v blowing the fuse?
 

flippineck

Sep 8, 2013
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sorry, did a few edits which you probably missed

You might get away with an 85Ah battery but for the small extra price I'd get a 100Ah or even 110Ah.

Regards the fuse, I'm with Arouse1973
 

Okiefrog

Feb 24, 2014
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Feb 24, 2014
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Update,
The plug in adaptor may have been bad, started eating the fuse in the car as did the replacement, I have a working one now but am really skeptical to try again
 

donkey

Feb 26, 2011
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ok if the new plug works then great. your concept is very much the exact way the wiring in a car is set out with the exception that in a car usually the ignition has to be on accessories for it to work.
Flippineck's estimate on the battery is correct and a 100ah deep cycle battery would get you close to where you need to be, however SLA batteries don't like going too low for too long so make sure it is charged daily to keep it in top performance.
personally I would love to come over and help you out with this one as its the easiest thing in the world.
your setup is very sound, I would look at finding ways to charge the battery as well just in case. you can try hooking it up to the car (it will need some modifications for 2 batteries to run well). I would triple check everything though before hooking it up to the oxygen tanks again just so your wife has her tanks when she needs them. a simple car to usb charger will suffice for testing. these can be had for very cheap (like $2 in some places) and will save you a lot of worry.
last but not least you said your original charger ate through fuses too so you used an inverter. as I said before your setup is nearly identical to a standard car setup so go ahead and continue using the inverter to make life easier.
now for the fun times. If you want an accurate read on amps then disconnect 1 lead from the battery and place a multimeter in the on amps. this will tell you how many amps it uses. multiply that by how many hours you want it to run for and that's the bare minimum AH rating to look for. I would actually double it. if it draws too much power then just keep adding batteries
best of luck
 
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