So I am trying to come up with a battery backup solution for some CPAP machines that would provide sufficient coverage for a few days if the power was out. Most CPAP battery solutions on the market are way overpriced and provide too little ah capacity. I needed a solution that would potentially cover 3-4 days use for 2 CPAP machines. I have a brand new Battle Born 12v DC 100ah LifePO4 battery and connected two 12v DC female connectors (each with their own inline fuses) to it which provides power to two CPAP machines running anywhere from 17-30 watts each (estimate round up to 75watts total due to fluctuation). Each machine is using their certified 12v DC power adapters. I tested the machines when plugged into 120v AC using a Kill-a-watt meter so I know it can bounce in the 17-30watt range depending on breathing (and not using the humidifier).
My question is can you leave this BlueSmart IP65 15a 120v charger connected and set for LION charging mode 24x7x365 AND draw upwards of 75watts load at night to run the CPAP machines? I did read on the product page you can leave this charger connected indefinitely which is fine. I couldn't find if this would automatically detect when the battery is low and top it back off to full charge. The confusion is if both CPAPs are running at night (for say 8 hours) it will drain the battery from 100% down to say ~85% or lower, would the charger kick on and feed the necessary power to charge the battery while the load is being supplied to the CPAP machines? Since the charger has specific algorithms for LION it wasn't clear how this could/would work or if it was supported.
I figured the 15A charger would be more than sufficient based on the estimated load. I would like to treat this almost like a battery backup solution in case the power goes out in the middle of the night, the battery would provide all necesarry power, then whenever the power came back on, the charger would just pick back up and continue to charge the battery until it hit 100%. One caveat might be that the charger wouldn't remember what battery chemistry it was configured for before the power outage and if it came back on it might default to lead acid or something.
The reason why I am pursuing this solution vs some out-of-the-box option is that I will get 10+ years off the Battle Born (with way more aH) + I can easily replace any component that might die along the way. I can also upgrade this to tie in a small 12v solar at a later time and use it to charge USB/mobile devices if the power goes out for a few days. More flexibility, better ROI and lifespan with this over anything else I can find on the market.
