(03-09-2015 03:17 PM)OperaSinger Wrote: Thanks for all the great info! I live where we have frequent power outages. We don't feel competent to set up a generator, so would love any advice and/or recommendations for batteries. We are wondering about the Lithium ones. We have been using a "portable power supply" that weighs as much as a boat anchor, and gets us both through about one night, without humidifiers. Hubby is on 12, and I was on 14. Now, the APAP test shows averages of 5.5-7 cmwp for me.
The lithium ones look expensive, but still cheaper and less dangerous than us trying to connect a generator.
I'm sure that insurance won't cover batteries, so I have been looking online and getting very confused about what we need. Although it looks like the prices have come down since I last looked 2 years ago.
Any ideas and suggestions would be much appreciated. Thanks!
Which lithium chemistry are you talking about? There is the Lithium Ion which is probably most common at the current time, but more volatile chemistry. There is the Lithium Iron Phosphate LiFePO4 chemistry which is a little bit less energy dense, but more stable and less prone to fire.
I would consider those for travel use because of small size and light weight and plan, when funds allow, to get a travel set up based on the LiFePO4 cells.
However, at the current time, I am still using the SLA (sealed lead acid) batteries I got a year or two back. They are either of the 35 or 39 AH sex. Since I will not use humidification on them, I am able to get a week or better, conservatively, out of each one. (I run an average pressure of 9 cm H2O). ResMed has a battery guide that shows power consumption/run times for their units in various configurations, Respironics does not. I have tested and measured power consumption on the Respironics to get my estimated current draw. I also figure in a 50% fudge factor (I size the batteries at 150% the computed draw in AH (amp hours) for a given period) to allow for several factors such as charge state, efficiency, age of the battery, etc. More accurately, I assume that the APAP uses 150% as much energy as what I think it actually uses, and use that figure to estimate how long a given battery will run the machine.
The 39 AH that I am using are about 25 pounds each, have built in handles, and are L: 7.70" X W: 5.12" x H: 7.02" in size. They are spill proof. And since they are in the house and I don't have to move them all that much, the weight and bulk of the SLA batteries is the way to go for me since they are MUCH less expensive that LiFePO4 batteries of equivalent capacity.
I use a BatteryTender charger to top them off every couple of months.
Mine are CSB brand model EVH 12390 batteries. You could check the specs directly at TNR Batteries' or any other dealer web site. Other comparable batteries are available - but mostly at 35 AH in that size/weight foot print. Probably the easiest way to attach this type of battery to your CPAP would be to hook up a cable that ends in a female cigar lighter plug, preferably one with an integral fuse, to the battery and get a Respironics DC auto cigar lighter cable to run between the battery and the unit (assuming a Respironics setup).
If you want links to some of these things, shoot me a PM and I can supply them directly without voiding the warranty on the apneaboard.com.
I tinker with electronics and I have direct wire setups using Anderson power pole connectors. But I also have radio and lights wired on the same platform. And even a USB charger for tablet/cell phone charging.
Do not ever, if at all possible, plug the power supply into a battery powered inverter for emergency power supply. Terribly inefficient. That takes 12 V DC power, burns some of it up converting the current to 110-120 V AC, then the converter turns that 110-120 VAC back down to 12 V DC - again using up power to make the conversion to get back where you started from.