DIY Portable Battery Pack-Update

Anonymous wrote:I doubt it would do any damage to the machine. The reason thease machines are rated at "12V" is so that they can be plugged into a vehicle. But in all reality a vehicle puts out between 13.8v and 14.4v your little battery pack isnt going to hurt anything.

I just wouldent be the one trying to get it past security at an airport.... that homade battery pack looks too much like the makings of a bomb as opposed to a comercialy built pack. Not saying they wouldent let you take it on, but if I were a TSA person I would be certianly questioning it. I know its just radio shack parts, but you know how the world is post 9/11

The instyructions tat came with my machine, say that you can run it off a battery, but should not use it while a car motor is running. To me this indicates that you do not want to run it off a 13.8V source....

The voltage in cars now is held to +-.02 volts by the regulator. If it is outside this range low, your battery is dying or the alternator has a bad diode. If high, you will be blowing bulbs and maybe an injector.
That home-built battery pack, if the proper voltage, won't hurt anything. Current rating is how much it can put out without damage to it's self.
ces44

Regarding the earlier comments.
Firstly from billbolton.
I had forgotten about the pressures at altitude, but if I got four hours sleep on a plane I would be amazed. My usual journey is between Boston and London and 2 hours would be magic.
Secondly from Tired-in-Nc
The input voltage is 13V and the current consumption is 0.75A at 20cmH2O
with a 4mm leak (from the manual). My pressure max's out around 12.
As the unit is designed for world wide the input voltage range must be wide. My pack gives out 13.86V each fully charged.
And Snooter
I will promise to wave if arrested.
But seriously the carrier I use asks to be informed about any battery packs and would hopefully pre-clear the packs with them. If not I will call in some favours and get the units cleared.
I have taken battery packs through before when I forgot, they didnt even open the box to check.

Billy

I tried the battery packs last night and they lasted for 7 hours 38 minutes.

Billy

It occured to me that my profile shows a Respironics Remstar Auto w/Cflex.
The tests were done using a Puritan Bennett 420e Auto.

puffing billy wrote:
As the unit is designed for world wide the input voltage range must be wide.

That is the design of the A/C power supply, it is variable in it's ability to supply the machine with it's correct working voltage over a wide range of a/c inputs. All the power supply does it reduce the A/C line voltage to 13 volt D/C, same as the D/C input plug. Jim

puffing billy wrote:I wanted a portable battery pack and decided to make my own.
Using 20 AA size nickel metal hydride batterys and standard parts this is what I made.




I calculated that with standard usage it should last me for nearly seven hours.
The reason that there are two pack is that the universal charger I have will only charge 10 at a time.

Billy

Do you know what type of battery is used in Respironics power pack? How many cells? What is the open circuit voltage after a full charge?

ces44 wrote:The voltage in cars now is held to +-.02 volts by the regulator. If it is outside this range low, your battery is dying or the alternator has a bad diode. If high, you will be blowing bulbs and maybe an injector.
That home-built battery pack, if the proper voltage, won't hurt anything. Current rating is how much it can put out without damage to it's self.
ces44

False: A normal car charging rate should be 13.4 volts to 14.4 volts, many go to 14.8 volts. The voltage is determined by the battery condition and outside temp, voltage regulators vary the voltage by design. Jim