Philips Respironics machines running on battery power

Philips Respironics CPAP machines actually operate at 12 volts, and I see that PR sells 12-volt battery packs for people who want to use their machine where normal household power isn't available.

Do any participants in this forum have experience running their machines on 12-volt power when the batteries are getting pretty run down? If the battery drops below say 11.5 volts, will the machine continue to run?

Some 12-volt devices, like LED light bulbs, will run just fine even when the voltage gets very low; other devices run erratically or shut down completely, and some I suppose might even get damaged.

calusa wrote:Philips Respironics CPAP machines actually operate at 12 volts, and I see that PR sells 12-volt battery packs for people who want to use their machine where normal household power isn't available.

Do any participants in this forum have experience running their machines on 12-volt power when the batteries are getting pretty run down? If the battery drops below say 11.5 volts, will the machine continue to run?

Some 12-volt devices, like LED light bulbs, will run just fine even when the voltage gets very low; other devices run erratically or shut down completely, and some I suppose might even get damaged.

It obviously shuts down at some point, but I haven't found where they publish an exact Voltage. I've run a number of times below 12, perhaps as low as 11.8, but that is common for partially discharged batteries. At 11.5, however, the battery is almost fully discharged so I would hope the CPAP would shut down rather than damage the battery. I would be very disappointed if it was possible for the pump to be damaged simply by low voltage.

One thing to note. Full charge for flooded cell lead acid batteries is 12.6 volts. !2.2 volts is 50 % discharged. The battery life will be much longer if it is not discharged to less than 50 %.

I've used my CPAP with the 12V cord many times. Works great and I get to go camping I do NOT use the hose heat or humidifier though as it's hard on the batteries. Plugged right into the RV where the TV would usually go. Looks like a cigarette lighter port.

Thanks everyone. My weekend hideaway has a huge battery bank, but the bank is quite old and the voltages are much lower than the "by the book" numbers.

Under a small load, the batteries can show as low as 11 volts and still have quite a bit of power left. I know it's hard on the batteries to run them down that far, but sometime there's not much choice -- for instance, when the sun hasn't been shining and I still need to breathe at night!

I've been running my machine off an inverter, which probably wastes as much power as the machine itself requires. Guess I'll work up the nerve to run it directly off the battery bank (without the humidifier and heated hose) and see how it behaves when the voltage drops way down . . . .

calusa wrote:Thanks everyone. My weekend hideaway has a huge battery bank, but the bank is quite old and the voltages are much lower than the "by the book" numbers.

Under a small load, the batteries can show as low as 11 volts and still have quite a bit of power left. I know it's hard on the batteries to run them down that far, but sometime there's not much choice -- for instance, when the sun hasn't been shining and I still need to breathe at night!

I've been running my machine off an inverter, which probably wastes as much power as the machine itself requires. Guess I'll work up the nerve to run it directly off the battery bank (without the humidifier and heated hose) and see how it behaves when the voltage drops way down . . . .

If its actually only putting out 11.0 Volts then it probably has a dead or shorted cell. This does not bode well, as a dead cell will bring down its neighbors. Actually, I'm surprised the inverter continued to work at the low voltage, since they should be designed to not kill the battery.

If its actually only putting out 11.0 Volts then it probably has a dead or shorted cell. This does not bode well, as a dead cell will bring down its neighbors. Actually, I'm surprised the inverter continued to work at the low voltage, since they should be designed to not kill the battery.

No dead cells; I monitor them regularly and all six cells are almost identical in voltage and specific gravity.

The battery bank is huge and the solar panels are relatively small; consequently the rate of charge is low and the battery acid gets stratified over time, causing the voltage to drop. When I run a diesel generator for a couple of hours, the high rate of charge stirs the acid up and the voltage returns to "like new" levels. So I do that every couple of months.

The inverter allows me to set the voltage level where the inverter drops out; I've set it pretty low (maybe 10.9?).

The battery bank is 15 years old, way past a normal lifespan, so I know it's living on borrowed time!