AC vs DC Battery Power - Better?

[SuperGeeky]

Hi All: After scanning various posts on battery backup, I chose to go out and buy a Black and Decker Electromate 400 at Home Depot.

After charging the new battery for 48 hours, I was able to run my Respironics BiPap Auto the entire night (eight hours). I used AC power and had the humidifier set to 'one'. Great success and relief for $100! Jumps the car and fills tires too!!

After reviewing several posts, I couldn't quite come to the conclusion if DC power will last longer. I noticed cpap.com has a DC cord for $24. Will DC last longer?

Also, is there a way to run the humidifier as well using DC Power? I've got two inputs on the B & W Electromate.

Thanks in advance, and also all who have posted their Battery solutions!!

Take care,

SG

[WNJ]

Straight DC power will definitely last longer. Much longer.

What you’re doing is converting 12 VDC to 120 VAC with the B&D Electromate. I’m not sure of the efficiency with which this device makes the conversion, but you will be losing somewhere between 10% and 50% in the conversion from 12 VDC to 120 VAC. Probably much closer to the latter.

The brick on your M Series will lose about 15% in converting the 120 VAC back to the 12 VDC the flow generator runs on.

Adding these together, you are almost certainly losing at least half the battery capacity due to the inefficiencies of conversion.

Running with the Respironics 12-volt cord, these losses would be entirely avoided. Your CPAP would probably run about twice as long between battery recharging.

If you have a convenient way to recharge the battery in the B&D every day, these inefficiencies won’t matter much.

Wayne

[DreamStalker]

Yep. 12 V DC is much more efficient ... get a deep cycle battery and an auto charger for most cost/energy effecient system.

Mine is taking a trickle charge right now for optimum capacity before Ike comes by to blow out the power grid

[SuperGeeky]

Thanks WNJ and Dreamstalker! So, ordering the $24.95 DC cord is a 'no brainer'.

When I spoke with the DME a few months ago, they recommended the Deep Cycle Marine Battery. And, they would sell me the DC adaptor for $80. I bet it includes the battery clips. They also commented that Respironics recommends the Marine Battery.

I know this is covered already in other topics, but just for a rehash. Dreamstalker, do you have an issue with Acid fumes? Or, is the Marine Battery not that type? And, how does one charge it after several uses??

I'm going to look at the humidifier, see if it can take DC as well. Perhaps together on DC, last a few days. That would be sweet

P.S. WNJ, from one Buckeye to another, go Bucks! Your in the heart of football country

[WNJ]

Dunno about the M Series, but my REMstar heated humidifier won’t heat on DC. I use it as a passover when camping.

Respironics DC cord will have a cigarette lighter plug on the end. You can get the cigarette-lighter to battery clip adapter at Radio Shack for about $7, rather than pay another $25 for the Respironics version.

For long life, a Deep Cycle battery is definitely the way to go. Be sure to look for one that is “deep cycle,” “RV,” or “trolling motor.” Any marine battery rated in “cold-cranking amps” (CCA) is not a true deep cycle battery. True deep cycle batteries will usually be rated in amp-hours only, not CCA and/or reserve capacity. Wal-mart has a true deep cycle battery for about $60. I use one and I can easily get 5 nights use out of it.

I keep my battery in one of the black plastic leakproof boxes they make for use in boats, about $7 at Wal-mart. If you want to avoid the lead-acid type of battery, you should look at AGM batteries.

Charging is a whole other issue. You will have to have a source of electricity. A power outlet or a generator and a battery charger, or a solar panel with charge controller.

P.S., I’m in Athens County -- the heart of Bobcat Country.

Wayne

[CorgiGirl]

Dunno about the M Series, but my REMstar heated humidifier won’t heat on DC. I use it as a passover when camping.

The older M series humidifiers were AC only, but the newest ones are 12v. These are also the ones with the better humidifier chamber (J-tube design). My hubby and I insisted on this model because we travel in our RV and often boondock without power hookups. So far, they are working fine for us.

[feeling_better]

have an issue with Acid fumes? Or, is the Marine Battery not that type?

IMO, non sealed batteries should not be used in a bed room. There is always some sulfuric acid evaporation from these. If you must, keep it far away from the cpap machine in let. The sealed batteries dont have this problem.

You have a number of other options. The one I am looking at is using a LiIo one used by popular lap tops. Many of these by alternate vendors have come down in prices, about a third of the oem price, now for about $60 online, with a capacity of about 12v/4Ah. That should readily last one night (likely two nights at lower pressures), without the humidifier. And they are only about one lb in weight, very portable.

Also there are small sealed lead acid battery with capacity 12v/4Ah available in our big local electronic super store (we are blessed to have one of those largest, discount one right here in Silicon Valley) for as little as $30. Of course, they are heavier, probably about 8 lbs, my guess.

These can be 'floated' on your current charger. That is they are connected in parallel on the output, DC 12v side, of your normal ac power supply, and they simply sit there, keeping almost full charge and wasting almost no energy. When the main electric power goes off, the battery will supply silently, without even skipping a beat. And when power comes back, it will automatically recharge, since, the cpap machines do have some extra capacity.

Of course if you are in areas where you have extended power outages for multiple days, you need a larger capacity battery.

[Goofproof]

Ideally I would want the lead acid battery in a battery case, outside of the house, a pain I know but not a unreasonable thing to do, the charger and wiring could be left inside, using the same two wired to go to the XPAP and charger. The type of charger matters, it need to be for Deep Cycle battery use, and be able to operate 24/7 without over charging the battery. Overcharging cooks the battery.

That Car starter Compresser, Jumper unit, the charger can run all the time without hurting the battery, but the option of recharging it with the car's electrical system can lower it's life span, as that can allow overcharging. Jim

[billbolton]

I’m not sure of the efficiency with which this device makes the conversion, but you will be losing somewhere between 10% and 50% in the conversion from 12 VDC to 120 VAC. Probably much closer to the latter.

No. Almost any contemporary inverter will be achieving at least 90% efficency.... there are plenty of efficient "shake the box" inverter approachs available at industrial design level now a days.

Cheers,

Bill (IEEE)

[Gerald]

The system "WNJ" has described is very close to what I have put together.

Gustav went right through my town....and we were without power for (2) nights.

Before the storm, I went to the Interstate Battery dealership and purchased the following:
(1) 35 Amp Hour Gell-Cell Deep Cycle Sealed Battery (the type used in electric scooters)
(1) 1.5 Amp Trickle Charger

I already had the following:
(1) Respironics DC Cord (purchased from CPAP.com)
(1) Cigarette Lighter to Clip Wire System (available from Radio Shack)
(1) Plastic Battery Container from Wal-Mart

Just before the storm, I charged my new battery all day with the trickle charger. It was 100% full when the storm hit....and the lights went out.

I slept through the first night very comfortably......using the humidifier in passover mode (no heat because it requires 110V)

I slept through the 2nd night very comfortably.

Before the 3rd night, power came back on at my office....and I was able to charge the battery with the trickle charger.

Late that afternoon, power came back on at the house....and I didn't need to use battery power for the 3rd night. For that reason, I don't know if the 35 Amp-Hour battery would have powered my M-Series for a 3rd night....or not.....but, I suspect it would have....even without charging.

My little back-up system is just right for me....and I can recommend the setup for anyone with a machine similar to mine (M-Series CFLEX Auto).

In addition, the battery will ultimately do double-duty powering the small trolling motor on my kayak.

Gerald

[Guest]

Hi All: After scanning various posts on battery backup, I chose to go out and buy a Black and Decker Electromate 400 at Home Depot.

After charging the new battery for 48 hours, I was able to run my Respironics BiPap Auto the entire night (eight hours). I used AC power and had the humidifier set to 'one'. Great success and relief for $100! Jumps the car and fills tires too!!

There are many here who will tell you this won't work. This is one setup I looked at too, the B&D. Home Depot and Sears both make some decent jump starters.

I was not able to find that Walmart batt. for $60 or cable for $7 and suspect those prices are a bit outdated.

I would just plan on using the humidifier in passover mode rather than worrying about it. After all you are just using it for emergencies, right? Just make sure it will work before hand.

Congrats Geeky

[WNJ]

I’m not sure of the efficiency with which this device makes the conversion, but you will be losing somewhere between 10% and 50% in the conversion from 12 VDC to 120 VAC. Probably much closer to the latter.

No. Almost any contemporary inverter will be achieving at least 90% efficency.... there are plenty of efficient "shake the box" inverter approachs available at industrial design level now a days.

Cheers,

Bill (IEEE)

The better brands of small pure sine wave inverters (e.g., Xantrex) will claim a "peak efficiency" of 85% to 90%. Look it up. Most of the time, in the real world, they will operate at somewhat lower efficiency. They will also cost much more than the $100 B&D and won't include the tire pump, radio, light, etc.

Inexpensive modified sine wave inverters don't generally publish claims as to efficiency, but you can bet they will be less efficient. See the substantial cooling fins? Feel how warm they get after the inverter has been run with a good load for a while. The heat they are dissipating is DC power from your battery that was lost in the conversion to AC output. That is inefficiency you can feel.

Wayne

[hobbs]

I would suggest looking at something like this. DRY cell technology = no acid to spill. Yellow Top is used by whack jobs that need 500 watt stereo systems in their CAR! Red Top is the best car battery I have used in 42 years of driving.

http://www.optimabatteries.com/optima_products/

[WNJ]

Gerald,

You might well have been able to run your CPAP another night on the 35 amp-hour battery, but that probably would have been the limit. I’m not sure how much power your M Series Auto will draw.

I seem to draw about 1 amp with my old REMstar Auto set at 10-14cm. Eight hours sleep is about 8 amp-hours drawn from my battery.

You should, if possible, avoid repeatedly discharging your battery much more than 50% as this will shorten its life.

Wayne

[WNJ]

There are many here who will tell you this won't work. This is one setup I looked at too, the B&D. Home Depot and Sears both make some decent jump starters.

I was not able to find that Walmart batt. for $60 or cable for $7 and suspect those prices are a bit outdated. . .

It will work, but with a 19 amp-hour battery don't count on it for much more than one night before recharging. And since the battery is not a deep-cycle, don't expect it to last through nearly as many deep discharges before meeting an early end. Your choice.

The deep cycle battery was $56.97 at my local Wal-mart a couple of days ago. I paid about $45 for one last year, but the price of lead has gone way up since then.

Sorry, I see the adapter at Radio Shack is now up to $9 since I bought mine. http://www.radioshack.com/product/index ... lt+adapter

Wayne