I recently purchased a Duracell backup battery from a specialty battery supply store for $119.00. It is an absorbent glass mat (AGM) type. (I have attached a picture below) It has a 55 amp hour rating. It took 16 hours to charge with a 1.25 amp Battery Tender charger when new.
I have used it a full night (8 hours and 53 minutes) to power my ResMed Autsense 10 Auto machine. I had both the humidity and the ClimateAir heated hose operating on Auto. About two thirds of the water in the humidity tank was consumed.
After the full nights use as above, it took 17 hours to charge the battery back to full charge at 1.25 amp hour rate. Battery Tender has a 5 amp hour charger available. I may order one of those. The 5 amp charger should charge it in one fourth the time which would make it more viable for multi night use.
I was using the 12 volt to 24 volt converter that is produced by ResMed. I intended to experiment with a voltage converter I rigged but the ResMed converter is superior. The ResMed converter has a circuit that will turn the converter off before it drains the battery to damaging levels which is a handy. Also, the ResMed converter converts the voltage very efficiently. The overhead power consumption was negligible. Much better than converting 12 volts to 120 and then back to 24 using an inverter and then using the normal ResMed plugin charger.
I will update as I get more experience with this setup.
Having spent a few years obsessing over telescopes and astrophotography the concept of batteries is key. All the best viewing locations are away from outlets. And you need to power the scope tracking system, cameras PCs etc.
This is what I use. Car jumpstarter / compressor
It has a 110volt plug.. but those are not efficient and will draw down battery faster. So I just ordered a 12 volt cable for my intellipap. It has the charging built in, sockets and you can inflate stuff and jump your car.
amazon UPG-84039-Adventure-Jump-Start-Compressor search Item id=1437842350 But there are dozens of these made by many makers.
I ran off the 55 amp hour Powercell AGM battery for 9 hours and 15 minutes. The ResMed A10 Autosense settings were for auto humidity and auto for heated ClimateAir hose. About 2/3 of the water in the humidity tank was consumed. The air conditioner for my apartment was set to 75 degrees fahrenheit. The indicated pressure for the evening was 10.9, also set to auto. The beginning voltage on the battery was 13.25 and the voltage reading this morning was 12.75. Based upon the voltage readings, the battery could easily supply two nights or more of usage at the above Autosense settings. Without the humidity and hose heater turned on, it could easily operate the machine for several nights. I am using the ResMed DC converter that is designed to plug into the cigarette lighter in a car (or other 12 volt supply). The converter is very efficient at converting the voltage to the proper 24 volts required by the A10, much more efficient than an inverter (12 volts DC to 120 volts AC) and then using the ResMed 120 volt power supply. I am sure that makes a considerable difference. I have tried using inverters with my amateur radio equipment and get relatively poor battery life compared to 12 volts direct without the need to operate off 120 volts AC.
I will provide more information as I develop data. I hope to post an article in the Wiki as I have more data.
PS. Sorry for the double post but I didn't want to leave this thread hanging.
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