Battery Backups - Car Battery Jumpers?

[kteague]

Let us know how you weather the storm and how your preparations work out for you. Stay safe!

[CollegeGirl]

Thanks Kathy! Will do!

[archangle]

From our host's page on the S9 DC-DC converter: "This converter also allows for use of the H5i humidifier and ClimateLine heated tubing with the S9 CPAP machines while on 12V or 24V DC power." [emphasis added]

Looking at the size of the DC-DC brick, I suspect it contains both a step-up transformer and a decoupling transformer / voltage limiter circuit. It does have the warning about connecting while the engine, so they may only be compensating for the fact that a fully charged lead-acid battery is 1.5 - 2.2 volts over it's operating voltage.

If you use 12VDC input instead of 24VDC input, the converter will have to run a step-up transformer in front of the voltage limiter circuit, which will drop the converter efficiency by anything from 12% to 25% depending on the design and components. Total runtime will reduce by a similar amount. By using 24VDC at the input, you SHOULD get virtually the entire runtime of the battery bank.

The "step up transformer" makes no sense for a DC-DC converter. It's going to be a switching power supply designed to take a large input voltage range. The AC power brick is a switching power supply that takes anything from 100-240VAC. If you look at the pictures, the converter looks a lot like the power brick.

We can start another thread if I need to explain switching power supplies further, but if anything, it will be optimized for 12VDC input, since that's more common.

The converter is very unlikely to be significantly better from a 24V source than a 12V source.

There is absolutely no need to go to the expense and extra hassle of two batteries, and a more complicated wiring and charging system to run the ResMed converter on 24V.

[sundevil]

Hey Collegegirl,

so what model of car jumper did you buy? did it work?

[archangle]

Since someone else bumped up this thread, I'll note one thing I've noticed one drawback about jumper batteries.

You may not get a night's run time from a day's charging time.

If you're planning to get multiple night's usage by finding a place with power to recharge the jumper battery during the day, it may not work very well. Some people want to run a generator for a few hours during the day to recharge, and that may not work, either.

If you use it overnight, run it down fairly far, and then recharge try to recharge them, it takes a long time to fully recharge them. I bought one of the DieHard 1150 jumper batteries. I ran my CPAP with humidifier off the jumper battery's inverter for about 4 hours and it showed something like 33% power remaining. It took 24 hours of charging before it was fully charged again. My Stanley jumper battery seems to have a similar recharge time.

The jumper batteries are designed for occasional use for short periods of time, not for night after night with a quick recharge during the day. The chargers are optimized for cost, and for recharging the battery without reducing the battery life.

You might be able to do a fairly quick recharge on one of these jumper batteries by hooking it up to a running car for a hour or two with the jumper cables, although this might not be good for the lifetime of the battery if you do it often.

[Burkebang]

archangle, that is a good observation which I have also made.

My jumpstarter battery is 18 amps and the charger that came with it is rated at just 500 milliamps. That means that a completely depleted battery takes 36 hours to recharge. My solution is to use a Ctec Zafir 45 charger attached to the battery clamps. This is a much better charger than the wallwort that came with the jumpstarter and it will recharge an empty battery in just over 5 hours.

SInce a full nights sleep should draw less than 6,5 amps, two hours of charging should be enough to fully charge the battery.

http://www.amazon.co.uk/CTEK-Zafir-4-St ... B004SMD6Q6

[archangle]

SInce a full nights sleep should draw less than 6,5 amps, two hours of charging should be enough to fully charge the battery.

I presume you mean Amp Hours. How do you come up with the 6.5 Amp number? I assume that's with no humidifier.

[avi123]

I tried this:



See it here:

http://www.sears.com/diehard-platinum-p ... 3344720095

It's NO good b/c:

1. Does not have enough charge to supply even 4 hours at 40 watts, i.e. not enough hours to run an S9 Autoset even without a humidifier.
2. After 4 hours it gets over discharged and starts emitting an ear piercing siren.
3. To recharge it back to 110 V it takes 36 hours.
4. As soon as you connect an XPAP to its 120 V outlet then a inside fan starts making noise as hi as a dishwasher running.

I need to return it, fast!

IMO, using a jump starter back-up for more than one night in a raw, is a dead issue.

[Lizistired]

I got 7.5 hours from my jumpstarter 1150, with 60% left in the morning. That and the other functions make it a worthwhile investment for me.

[Burkebang]

SInce a full nights sleep should draw less than 6,5 amps, two hours of charging should be enough to fully charge the battery.

I presume you mean Amp Hours. How do you come up with the 6.5 Amp number? I assume that's with no humidifier.

Thank you for the correction, it is of course amp hours I mean. I have read about several people meassuring the actual current draw from their machines and the general number I have come up with for such calculations is that a CPAP will draw ~0.8 amps continously when in use. 0.8 amps X 8 hours of sleep = 6.4 amp hours needed from the battery.

I allways calculate backup power without heated humidification. But the humidifier can be used in pass over mode.

Since my jumstarter has a 18 amp hour battery, it should power my CPAP for 18 / 0.8 = 22 hours.

[chunkyfrog]

I am toying with the idea of getting a 8000mAh 12 v Li-poly battery (under $50)
and joining it with an appropriate balance charger and power supply.
A make-up case or child's purse ought to hold everything.

[Burkebang]

It's NO good b/c:

1. Does not have enough charge to supply even 4 hours at 40 watts, i.e. not enough hours to run an S9 Autoset even without a humidifier.
2. After 4 hours it gets over discharged and starts emitting an ear piercing siren.
3. To recharge it back to 110 V it takes 36 hours.
4. As soon as you connect an XPAP to its 120 V outlet then a inside fan starts making noise as hi as a dishwasher running.

I need to return it, fast!

IMO, using a battery back-up for more than one night in a raw, is a dead issue.

You need to turn off your humidifier or use it in passover mode. In theory you should get ~27 hours of use from that nice looking jumpstarter if you had a 12 volt CPAP machine. Considering the overhead from the inverter, you should get at least 2 nights of sleep.

You can easily charge the jumpstarter with a more powerful charger, like this: http://www.amazon.co.uk/CTEK-Zafir-4-St ... B004SMD6Q6
Just connect it to the battery clamps and use it for bulk charging. The charger that came with the unit can then be used for maintainance charging.

[avi123]

You need to turn off your humidifier or use it in passover mode. In theory you should get ~27 hours of use from that nice looking jumpstarter if you had a 12 volt CPAP machine. Considering the overhead from the inverter, you should get at least 2 nights of sleep.

You can easily charge the jumpstarter with a more powerful charger, like this: http://www.amazon.co.uk/CTEK-Zafir-4-St ... B004SMD6Q6
Just connect it to the battery clamps and use it for bulk charging. The charger that came with the unit can then be used for maintainance charging.

Questions,

1) What is a 12 volt CPAP machine? I can use this converter plugged into the 12 volt outlet from the JumpStarter to run an S9 Autoset. It would be instead of the standard 90 watt 110 volt (or a 30 watt, 110 volt, power supply, to run the machine without a humidifier, in this case):

Resmed DC Converter 24V/90W For S9™ Machines

"The ResMed DC Converter for S9 machines enables S9 Series CPAP Machines to be powered using a 12V or 24V power source such as those found in a car.

(No use for the alligator clips)



costs about $85

In this case the estimated usage time is about 7 hours.

2) What is an overhead of an inverter?

I tried the following with the Dieard 1150 JumpStarter:

The machine was partially charged at Sears before I picked it up.
After I charged it for additional 12 hours to 100%, I stopped the charging and I plugged a 40 Watt bulb into the 110 Volt AC outlet of the inverter. 40 watts could run an S9 Autoset or S9 Elite, for 8 hours, but without the humidifier. But, after about 4 hours of running (lighting the bulb) , the voltage at the inverter outlet dropped from 113 volt to 106 volt. After less than 30 min the bulb stopped lighting and the machine started to emit a hi pitch ear- piercing sound, probably an alarm of being over discharged to zero. It took 36 hours (without load) to charge it back to 100%. During the charging the machine can't be used.

[Burkebang]

Questions,

1) What is a 12 volt CPAP machine? I can use this converter plugged into the 12 volt outlet from the JumpStarter to run an S9 Autoset. It would be instead of the standard 90 watt 110 volt (or a 30 watt, 110 volt, power supply, to run the machine without a humidifier, in this case):

A 12 volt machine is a machine where the powersupply feeds the machine with 12 volt power. Then you can get a cable that attaches directly to a battery, without using a powersupply at all. The Resmed machines use 24 volt from the powersupply, so it needs the DC converter you link to when connecting to a battery. Your jumpstarter has an inverter buildt in to it, so you have the option of using your mains power supply and connect it to the AC output of the jumpstarter or use a DC converter supplied by 12 vol power.

2) What is an overhead of an inverter?

An inverter uses quite a bit of power to convert 12 volt DC into 110 volt AC. This is wasted power that turns mainly to heat in the components in the inverter. It is this lost power I refer to when I talk about the overhead of the inverter. So if you have the DC converter, there is less converting of power going on and much less power lost in the conversion process.

I tried the following with the Dieard 1150 JumpStarter:

The machine was partially charged at Sears before I picked it up.
After I charged it for additional 12 hours to 100%, I stopped the charging and I plugged a 40 Watt bulb into the 110 Volt AC outlet of the inverter. 40 watts could run an S9 Autoset or S9 Elite, for 8 hours, but without the humidifier. But, after about 4 hours of running (lighting the bulb) , the voltage at the inverter outlet dropped from 113 volt to 106 volt. After less than 30 min the bulb stopped lighting and the machine started to emit a hi pitch ear- piercing sound, probably an alarm of being over discharged to zero. It took 36 hours (without load) to charge it back to 100%.

If you are totally discharging your 22AH battery in 4 hours, you are putting a load of 5,5 amps on the battery. A 40 watt load on 12 volt power draws 3.3 amps. The difference between 3.3 A and 5.5 A is the loss of power in the conversion process.

My PRS1 is spec'ed at a maximum power use of 3 amps. That is with the humidifier on full and while spinning up to max pressure, worst case scenario. When in operation at normal pressures, it draws ~0.8 amps, with the humidifier turned off. You can use this number as an average for calculations.
So if you exchange your lightbulb for your CPAP, you can get a rough idea by taking the 3.3 amp pull of the lightbulb and divide it by the 0.8 amp draw of your CPAP, then you should get 4.1 times longer use out of your CPAP, that is roughly 16 hours of use if you connect the mains power supply of your S9 to the AC outlet of your jumpstarter
If you connect your machine with a DC converter to the 12 volt output of the jumpstarter, you'll get much longer usage time.

You can safely hook up your machine to the jumpstarter and try it for a night, then you'll see how much power is left in the morning.

I'd hold on to that jumpstarter if I was you. It has a lot of features and a high capasity battery

[avi123]

You can safely hook up your machine to the jumpstarter and try it for a night, then you'll see how much power is left in the morning.

I'd hold on to that jumpstarter if I was you. It has a lot of features and a high capasity battery

Reply,



What if I take your suggestion to try the Diehard JumpStarter and hook my S9 to it for the night sleep and the JumpStarter's charge gets depleted after 5 hours while I am still asleep? I use a traditional nasal mask which has no anti-asphyxia valve. In addition my mouth is kept closed by a chinstrap. So how could I breathe if the machine stopped suddenly? Notice that I am not like one of your floor sweeper machines. I am a human being!