How to Charge the Resp. Universal Battery from another 12v..

[Bogof]

Hi,

I have the Respironics Universal Battery Pack (1028869) which powers my M Series Auto CPAP nicely via the Shielded DC Cord (1001956).

I re-charge my battery with the supplied mains charger adapter.

But on the next trip I won't have mains power available to me so I would like to re-charge the battery pack from another battery, like the one in a camper van.

I looked on the Respironics website and battery pack related PDFs but can't find what I think I need.

The battery has a 'female' cigarette lighter plug in which the normal charger connects via its 'male' cigarette lighter ends. So the bit that goes into the battery is definitely a male cigarette lighter. Nothing else fits. On the other end of the cable I need must be either a male cigarette lighter so I can just stick it in the van's cigarette lighter socket, or those red and black crocodile clips so I can connect it straight to the battery. Ideally the former, but the latter will do.

Respironics don't seem to do a cable that has a male cigarette lighter plug on both ends. Neither one that has a male cigarette lighter on one end and crocodile clips on the other. Googling around didn't bring me any such cables either.

Can any one suggest a solution as to how I can re-charge my portable battery pack from a car battery?

[Goofproof]

Use a Inverter, to power the charger. That should work unless for some reason the charger has a problem with squarewave. Jim

[Bogof]

Thanks Jim!

My understanding of inverters was that they tend to be quite inefficient resource hogs. It seems odd to me (not an electrician by any means) that you'd have to upscale to 240 from a 12V battery only to plug in the standard battery charger which downscales from 240 back to 12.

If that's the only way then so be it!

[Goofproof]

Your Respironics Universal Battery Pack, was designed to be charged with it's adaptor. Sometimes trying to charge things with a charge that wasn't intended can damage the batteries, even cause them to explode.

Using a Inverter is a inefficient way to recharge, but it should be a safe way.
Ideal would be to use your charger on your A/C. You could recharge from another D/S source, but the Source Voltage would need to be controlled and the recharge Amperage would need to be limited to safe recharge levels. Failure to do that could result in cooking the battery, and even explosion.

I assumed you were think about using your car power to recharge, the range of correct car voltage range from 13 to 14.4 Volts D/C, however with charging problems that can vary quite a bit. I once worked on a police car that had over $5,000 worth of radios replaced, before they finally got it to me, so I could finally find the problem and repair it. I was the third mechanic to work on it. Jim

As long as a Invert is being used while the car is being driven, Resource Hog doesn't apply, as the Alt will step up to cover the load.

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CPAPopedia Keywords Contained In This Post (Click For Definition): respironics, Power

[Bearded_One]

At best, trying to charge a battery pack like that using a double ended DC power cord won't work -- at all. At worst it could damage the battery and/or the internal electronics, and it could cause a fire. As was already mentioned, an inverter would be the safest way to charge it.



Lithium battery fire

[GeneS]

If you still want to pursue a battery you can find a DC Voltmeter at Radio Shack or similar store. I have one that goes to 30 Volts. Large Truck Stops usually sell both male and female car cigarette lighter adapters. If you check the polarities and voltages of the machine with its adopter and with your battery and make sure they are correctly connected you can assemble an adopter that should work. If AC power is available an inverter would be a good way to go.
GeneS

[Goofproof]

If AC power is available an inverter would be a good way to go.
GeneS

A Inverter, changes D/C Voltage into A/C Voltage that you can plug your battery pack charger into. All you need is a battery and the correct inverter to get to the chargers requirements.

[billbolton]

The battery has a 'female' cigarette lighter plug in which the normal charger connects via its 'male' cigarette lighter ends. So the bit that goes into the battery is definitely a male cigarette lighter. Nothing else fits. On the other end of the cable I need must be either a male cigarette lighter so I can just stick it in the van's cigarette lighter socket, or those red and black crocodile clips so I can connect it straight to the battery. Ideally the former, but the latter will do.

Just plugging any rechargeable battery directly into a DC power source to recharge it is never a good idea. There always needs to be something to limit the charging current to safe levels, even if it is just a simple resistor.

Rechargable Lithium-Ion batteries are not like rechargeable Lead-Acid, Nickel-Cadmium or Nickel-Metal-Hydride in that they are not ammenable to simple charging approaches and require considerably more care in charging. Simple constant curent and other similar charging modes are not generally recommended for Lithium-Ion batteries.

Directly connecting any battery pack to another DC power source without some charge management electronics to mediate the charging process is very definitely not recommended!

Another problem with recharging from automotive batteries is that the terminal voltage of the source battery will generally not be high enough to put a full charge into the battery under charge. In many cases the full charge terminal voltage of both batteries will be so close that a full charge cannot be achieved for the battery under charge.

You really need a voltage source that is ~20% higher than the desired terminal voltage for the battery under charge, to be able to fully charge it.

There are probably low voltage solutions available for your problem but they certainly won't be a simple as a piece of wire and a couple of connectors. I don't have any personal experience with Respironics battery packs so can't give you specific advice on that approach.

The advice above to use and inverter to power the AC charging adapter is probably the most straightforward approach on a plug-n-play basis.

Cheers,

Bill

[Bogof]

Thanks guys, that spells it out nicely. Cheers Bill, bump into you everywhere these days

I will investigate the inverter route. Thanks a lot!