2oldman wrote:
A 12 in parallel with 2 6s should work.
not really. the issue is that unless the 12V is the same AH as the 6V the 12V will discharge faster than the 6V bank and the 6V bank will end up charging the 12V and you'll end up with well under the assumed AH
better thing would be to use a battery selector switch to select one or the other.
now I expect Mex to chime in and give more details and/or shoot my analysis down.
And unless the CPAPs are also running with the humidifier on, a pair of GC batteries will go many weeks even running two CPAP's. Data on three different CPAP machines, a resmed, a resperonics and one other from another member indicates an average current draw of an amp or less.
My resmed will run 4 1/2 nights off a 250WH (that's around 20AH) lithium battery pack.
and residual draw in my trailer over night from propane detectorm fridge electronics etc. is about equal to the CPAP.
Now turn on the tube heater and heated humidity and it will run the draw up to about 3A average or 25AH, even that will go many nights on a pair of GC batteries.
