Battery Back-up Project complete!

[WilsonVilleUSA]

Goal:
Battery back-up to get thru the night (or two nights) in the event of power outage.

Requirements:
-Reasonable cost (<$150)
-Automatic- no waking up to alarms, switching things around, starting generators.
-Power not one, but two APAPs, and the humidifiers as well.

Options I looked at and rejected:
-CPAP.com battery pack. I have one and it is great for a night on the road, but doesn't power humidifier. Not a long term solution/inconvenient (oops! forgot to charge it)
-Computer type UPS. Will power humidifier since it has inverter, but not enough life to last more than an hour or so.
-Generator. Have a small one, but don't want to hassle with fuel, noise, hooking it up in the middle of the night, etc.

Nothing on the market (that I am aware of) that meets the requirements or accomplishes the goal. So I decided to cobble together my own custom back-up unit.

There are several warnings in the forum about the need for "Pure Sine Wave" inverters needed to power CPAPS and their HH units. My wife and I both use Remstar M series Pro APAP w/heated humidifier. The APAPs run on 12v dc, conversion done in the power supply. The HH uses AC.

I contacted Respironics asking about the requirements and they told me the M series HH would be fine on a "standard" inverter (ie "Modified Sine wave) but to make sure it was rated for a minimum of 300 watts.

That hurdle cleared, I began to gather parts. They are:

-Battery- $65 from local battery house. General purpose sealed lead acid lawn tractor type, 35 AH rating.
-Inverter- Xantrex 400 w/digital display. I already had this, If I recall correctly it cost about $35 at Costco.
-Automatic charger- Schumacher 1.5amp charger. $18.44 at Wal-Mart.
-Misc wire/terminals- $4.00 at the battery house.
-Attractive case- $4.97 six-pack cooler from Wal-Mart

Total- A touch under $119 with tax.

Hooked it up and viola! Battery backup that can have the units plugged in and be always "on-line". Units run off the inverter and battery, battery consatantly being charged. If power goes out, don't even have to get up and do anything.

We slept on it for two nights (without battery charger plugged in) with HH's in passive (no heat) and it worked great. The machines were kept plugged in even when we weren't sleeping, so there was always a draw going.

I haven't yet tested it's full capacity, will do that later this month to see how many nights can get on a charge. I expect it will do 2 machines for 3 nights on the inverter with passive humidifier use.

For longer term use, I also wired a 12v receptacle to it, so machines can be powered off the DC cord and get even more life by not using humidifier and bypassing the losses from the inverter. I also plan to test capacity in this configuration. My rough numbers tells me to expect about 8-9 nights for a single machine.

It is a fairly small package, the cooler encloses the battery and all the wires. Charger is left out for air flow and cooling, inverter sits on top and is held in place with bungee cord hat came on the cooler. I am pretty happy with the way it turned out and no longer fear waking up to the sensation of suffocation.

[TXKajun]

WOW! Thanks for passing along all the GREAT info!!

I think you're probably gonna be up for a major lab rat award!! (And that's a good thing!)

Kajun

[Nodzy]

Jackpot!! That is a fantastic package, and at a very reasonable cost. Thank you for sharing the details and great shots of the package.

Nodzy

[tuna]

So how long will the charge last with the HH on, not in passive?

What happens if the inverter an such malfunction and overheats?


Just looking at a possible problem.. The idea if a good one though..

[LyleHaze]

Excellent project, nicely done.

If I may offer a few questions:
I recall reading that running the APAP directly off your car should be done only when the engine is not running.. i.e. not while charging the battery, as the "charging" voltage is higher than the straight battery voltage.

Battery chargers often get to 14 + volts while charging, that may be a bit high for the APAP.

Lead Acid batteries give off hydrogen when charging or discharging. It might be a good idea to keep the battery outside, and run a cord in to your machines.

Nice package though, very accessible.

LyleHaze

[Sergey45]

As a very lazy person I like when some one is doing a research and presenting it to me. Great job.
Very useful information.
Thank you very much.

[WilsonVilleUSA]

So how long will the charge last with the HH on, not in passive?

That is yet to be determined. We generally don't have them on, but given the increase in power consumption I measured, I would expect on a low setting it would still be good for at least two days.

What happens if the inverter an such malfunction and overheats?

Uh, then I guess it would quit working (duh). Inverter has a fan in it that cycles on and off as necessary, and the heat it generates is why it is outside of the cooler.

[WilsonVilleUSA]

Excellent project, nicely done.

If I may offer a few questions:
I recall reading that running the APAP directly off your car should be done only when the engine is not running.. i.e. not while charging the battery, as the "charging" voltage is higher than the straight battery voltage.

Battery chargers often get to 14 + volts while charging, that may be a bit high for the APAP.

Since it will primarily be used off the inverter, this isnt' an issue. Yes the charger will go up to 14.4 volts while charging, but it is the inverter taking that and changing it to 115 VAC. In a case where I needed max capacity and used the DC hook up, I would not have it plugged in during CPAP use, instead charging it, then disconnecting the charger for use.

Lead Acid batteries give off hydrogen when charging or discharging. It might be a good idea to keep the battery outside, and run a cord in to your machines.

The battery sits under an open window (we keep it open year round) and usually have small fan blowing as well. Additionally we have a whole house fan that is usually running. With pretty good air circulation, I am not terribly concerned about this.

While it is intended to be always on-line, in actual use I expect to only use it when weather is such that I am concerned about an outage. This is to save wear/tear and charge/discharge cycles as well as no need in wasting the electricity lost in the inversion process.

[wildmt/guest]

Very good report. I have thought about taking a Sport Pac portable power generator I have and doing the same with it. It has two outlets on the inverter for AC use plus a DC outllet in front. Since a recent power outage here, I gave this idea more thought, and like WilsonVille USA, figured the Sport Pac battery could be plugged in for constant charging and when the power should go off at night, we (my wife and I are both APAP users) would never know the difference till morning. My only reluctance is about the general safety of doing it. The Sport Pac cost me $100 at Cabela's a couple years ago.

[rested gal]

I think you're probably gonna be up for a major lab rat award!! (And that's a good thing!)

Kajun

I think you're right, Kajun.

[rested gal]

Excellent job, WilsonVilleUSA!

Congratulations...

[Bearded_One]

Very nice rig and a very nice write up.

A couple of comments over concerns about safety that were expressed:

The sealed lead acid battery releases little or no hydrogen while in use.

There is no reason to believe that the inverter is any more likely to overheat than any other electronic power equipment, including the UPS's that are ubiquitous in many offices (and in my living room)

[odawa]

Wonderful!!! Thank you so much. I really like the pictures of what is needed. Iknow in other articles products were mentioned, but I had no idea what they are. I'm not electrically savvy, well to a point, I've never have to figure out the watts and volts and such. Thank you, now I know what I need!!!!