Battery Backup Design

Breathe Jimbo wrote:JohnB, how long have you had your battery backup system, and has your battery ever exploded?

LOL! Sorry. While I understand it's an honest question, it just strikes me as funny.

But the topic is NOT funny. Anyone that considers putting in a battery backup in their house should take some VERY clear steps to make it as safe as possible. There is a LOT of power stored in one of these deep cycle batteries.

Let's see. Let me tackle the first question. I bought a battery as a backup device in my old house (we moved about 12 years ago). I think I had it for at least five years before that. Until I published this design, I had kept the battery in the garage. Of course, that tends to drain the battery much more quickly.

The combined desire to have a safer solution and a battery that will last longer pushed me toward this design.

By using a good float charger, by checking that it is working every couple months, I hope to eliminate most issues. I also check the battery (inside the case) on an annual basis. As it gets older, I will check it more frequently. If it takes longer to charge and/or does not hold enough of a charge, then I will swap the battery for a new one.

A lot of battery explosions result from either improper handling (a short) or charging them too aggressively. By using a small float charger, this design eliminates one problem. The design of the cables and terminal covers is intended to eliminate problems with shorts. It's even possible to place a fuse into the cabling to avoid a short outside the box.

However, it is still possible the battery might short out within and explode. That is a *very* rare situation. The best insurance against that is to purchase a product with a good reputation - and to purchase a battery that can handle the demand you will place upon it. If the battery has a good reputation and is designed for deep cycle operations, that type of short out should not occur.

Also, that is why I purchased a battery case for the battery. If something like that should happen the battery case would contain the carnage.

That's the long answer.

The short answer - About 17 years and I've never had a battery explode.

JohnBFisher wrote:I agree with GumbyCT on this. The manual notes the amperage needed for AC is only 2.1. The amperage for DC should actually be a little less. Sounds as if an engineer said "Well, 5 should be high enough for anything!".

Minor correction. The mfr's spec says 100 - 240 v, 2.1 amps. I would take that as meaning the 2.1 amp is the highest expected current draw which would be at 100 volts. At 240 volts the max amps would be about 40% or .8 amps. At 100 v ac 2.1 amps will be 210 watts. Divide 210 by 12 volts dc you get 17.5 amps max draw. 12 v and 5 a is 60 watts. The numbers are almost meaningless since there's so much discrepancy between the mfr listed ac power requirement and the mfr listed dc power requirement. For battery sizing I would be inclined to go with the 6o watt, 5 amp, number, plus some margin.

idamtnboy wrote:

JohnBFisher wrote:I agree with GumbyCT on this. The manual notes the amperage needed for AC is only 2.1. The amperage for DC should actually be a little less. Sounds as if an engineer said "Well, 5 should be high enough for anything!".

Minor correction. The mfr's spec says 100 - 240 v, 2.1 amps. I would take that as meaning the 2.1 amp is the highest expected current draw which would be at 100 volts. At 240 volts the max amps would be about 40% or .8 amps. At 100 v ac 2.1 amps will be 210 watts. Divide 210 by 12 volts dc you get 17.5 amps max draw. 12 v and 5 a is 60 watts. The numbers are almost meaningless since there's so much discrepancy between the mfr listed ac power requirement and the mfr listed dc power requirement. For battery sizing I would be inclined to go with the 6o watt, 5 amp, number, plus some margin.

You are mixing the AC and DC formulas. There is another factor for AC. That's why the disparity. Keep it simple 5A is more than enuff for DC with blower at 20cwp.

GumbyCT wrote:You are mixing the AC and DC formulas. There is another factor for AC. That's why the disparity. Keep it simple 5A is more than enuff for DC with blower at 20cwp.

Watts is watts whether it's ac or dc. Volts x amps = watts. AC wattage can be influenced by power factor but that's a non-issue in this kind of situation. Strictly speaking for ac it's volt-amps but for all practical purposes that's the same as watts.

For flow generator only I agree, 5 amps is plenty. With humidifier though the load can be over 11 amps for the S8 and 7 amps for the S9.

Wolftracker didn't say if he needed the power number for a 12v to 120v inverter, or for direct 12v connection. Makes some difference, though the amp draw from a battery should be close to the same in either case. But, for a 70 watt CPAP Resmed recommends a 150 watt modified sine wave inverter, twice the brick power rating.

Now your mixin R's.

wolftracker wrote: Does anyone know where to find the power requirement for the PR ONE with AFlex.

The 5A will include the humidifier.

Guys,

I was hoping not to blow my house up.
I want to use the apap + humidifier
I bought the 300 watt DC to AC power inverter and
the 12v DC power cord. I am now thinking I can use one
or the other, I dont have to do both.

I have never built anything in my life and thought the design
of this would be kind of easy to build. I know you put a battery
in a flashlight and it usually works... That is about it.

We are talking about doing an RV Camping trip. Again a first
for me. Have not camped since boy scouts. This was a couple of years
ago.

So be gentle. I have all the parts I need right now except for the battery.
I was thinking about getting the largest battery in the 24 range I could get.

I figured that would give me more days in case they are needed.

Can you point out where my fussy thinking is off.

Also I was thinking the the power charger company also has a solar charger model
out there. I was wondering it that would extend the time the machine could be used

and what the down size of that would be

thanks
wolf

Well, let me take this apart a few steps at a time.

First, of all you mention you ...

are talking about doing an RV Camping trip. Again a first for me. Have not camped since boy scouts. This was a couple of years ago.

So, I have a bunch of questions associated with that:

• Will you be camping at sites with power?
• Will you be camping at sites without power?
• How long will you be at sites without power?
• Will you be traveling during the day?

You get the gist of the questions. If you plan on being at sites with power, the battery backup is not as necessary. If you intend on *almost* always having power then battery backup becomes more important. If you plan on rarely having power, then it might even be problematic.

On the other hand, if you plan on driving for quite some time each day, you can use the 12V DC power to charge the battery during the day.

You see why the answer quickly becomes "It depends ..."

As to use of the humidifier and/or the unit, I would recommend *not* using the power on the humidifier. It will act as a "passover" humidifier. You can still put distilled water into the humidifier and it will moisten the air a little. That is a good compromise between no humidifier and heated humidifier.

As to the question about the solar charger, most of those units would not put out enough amperage to charge a deep cycle battery. They are costly and unless you plan on being in the sun for a long period of time have minimal benefit.

Also you mention ...

I have all the parts I need right now except for the battery. I was thinking about getting the largest battery in the 24 range I could get.

Pardon me for asking ... Did you mean 24 amp hours? Or were you talking about a brand? Or ...

Again the number of amp hours for the battery will depend on how frequently you are able to charge it, how frequently you will use it, and how long you will need to use it (one night versus one week).

Don't be afraid to ask Respironics, since you have questions about the power needs. Also, remember that battery stores should be able to also help properly size the battery. It never hurts to ask.

Hope that helps.

The 24 is a group 24 and is the box you bought...i blew up the picture to get the part number
and got the same part. So I thought about the largest group 24 deep cell battery

Camp grounds, I hope mostly camp grounds with electricity.

We currently plan on driving across country and around a bit. Might be out 30 - 60 days
or there about.

We were talking with the guys from the battery store and they wanted to know how big a draw
the CPAP used. That is what started this and I have the 5AM number now.

Resporonic has not emailed us back with the true amount of power needed.

I think that is most of the questions



wolf

I was just trying to add up battery experience including me and my immediate family. It adds up to something like 160 "battery years" with no battery dangers other than occasional small amounts of leakage out the top or spilled from turning the battery over. That's counting me, mom, dad, multiple cars, trolling motor batteries, backup deep cycle batteries, etc. It only counts "car battery" size lead acid batteries.

I don't know of any car battery/marine battery explosions among any close friends who probably would have mentioned if such a thing had happened to them.

archangle wrote:I don't know of any car battery/marine battery explosions among any close friends who probably would have mentioned if such a thing had happened to them.

My brother had a battery explode one time but I don't recall the details. It does happen, rarely, if there is hydrogen gas leaking out and you have an ignition source. The ignition source probably is always when a cable is touched to one of the terminals while connecting the battery for something like jump starting. That's why the admonition is given to always make the last connection away from the battery, not on the battery. For jump starting you should connect the last clip to the engine or frame for the ground or negative lead, several inches away from the battery. A totally sealed battery, or one with really tight fitting caps will hardly ever be leaking H2.

On this boating forum http://www.thehulltruth.com/boating-for ... plode.html several guys discuss their experience with batteries exploding. I seems like the most likely other cause for an explosion is a very high current draw that causes a breakdown internally, or two plates deteriorated to the point of touching, causing an internal short. Both of these conditions would be extremely rare with a deep cycle battery being used to power a CPAP.

I admit I don't always follow the admonition, and have never had a battery explode.

In summary, a battery explosion is possible, but extremely unlikely. The probability is so low I would concentrate more on safe driving to avoid having an accident on the way to the grocery store!

FWIW, I keep a Kill-a-Watt plugged into the receptacle on my UPS and it indicates my S9 Autoset initially uses about 55W heating the water in the humidifier, but then ramps down to between 25 and 30 W while running throughout the night.

Keeping a 12V wet battery on a float charger or Battery Tender, you won't generate any hydrogen to speak of.

Slartybartfast wrote:Keeping a 12V wet battery on a float charger or Battery Tender, you won't generate any hydrogen to speak of.

Except for hydrogen within the battery case itself. Don't take the caps off and check the water level with a match or with a cigarette in your mouth. Don't put the battery in an airtight case, either.

Info I received back from Phillips:

There is no power specification by setting for that device. The amount of power used varies little between settings.

CPAP - DC Power Consumption: 12 VDC, 5.0 A

Humidifier - DC Power Consumption: 12 VDC, 5.0 A

Exact specifications for battery power consumption is difficult because of environmental factors, battery charge level and age. Our specifications are high based on peak consumption. Most people that use CPAP devices on battery will only use the humidifier as a Passover (without power) thus increasing run time by 50%.

A 100 amp/hr battery will run our device approximately 20 – 25 hours. It is encouraged that you test the battery at home with the equipment for duration time.

Thomas E. Dubé

Customer Service Representative

Sleep VIP and Patient Information Services

Philips Respironics HHS

archangle wrote:

Slartybartfast wrote:Keeping a 12V wet battery on a float charger or Battery Tender, you won't generate any hydrogen to speak of.

Except for hydrogen within the battery case itself. Don't take the caps off and check the water level with a match or with a cigarette in your mouth. Don't put the battery in an airtight case, either.

Every battery box I've ever seen has vents in the top to release hydrogen. If you use a store-bought battery box it's really not a problem.

Slartybartfast wrote:

archangle wrote:

Slartybartfast wrote:Keeping a 12V wet battery on a float charger or Battery Tender, you won't generate any hydrogen to speak of.

Except for hydrogen within the battery case itself. Don't take the caps off and check the water level with a match or with a cigarette in your mouth. Don't put the battery in an airtight case, either.

Every battery box I've ever seen has vents in the top to release hydrogen. If you use a store-bought battery box it's really not a problem.

All the commercial marine style battery boxes I've seen look like they are not airtight enough to not be a problem in the kind of usage we're talking about.

If you decide to build your own box, use a box made for something else, or use something like a Tupperware container, you might have a problem. There might also be some battery boxes that are intended for things like explosive environments that are sealed and might hold hydrogen in.