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ipyakuza asked

Blue Smart IP65 Charger CPAP Battery Solution

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.

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2 Answers
snoobler avatar image
snoobler answered ·

CPAP consumption varies, particularly if you use a heated humidifier. I have a ResMed S9. it uses about 250Wh/day including the AC-DC conversion in the power brick, but I only sleep about 6 hours per night. This also counts leaving it plugged in all day and consuming a small background load. If you only have it powered when in use, you can probably shave off 20-25% of the use in a 24 hour period.


A BB 12V 100Ah has 12.8V * 100Ah = 1280Wh or 1280/250 = 5.12 days of powering my CPAP.


So, unless you KNOW how much your CPAP uses, you can't really be confident you have your 2X CPAP covered for 2-3 days. Two probably, and if you don't use heated humidifiers, you can likely get three - maybe more.


Here's how I would set it up:


IP65 charger operating in power supply mode set to 13.7V. This would hold the battery at 95-98% charge indefinitely.


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The CPAP would draw from the battery. As soon as the battery voltage drops below 13.7V, the charger would start feeding additional current, up to 15A, to raise the voltage back to 13.7V. Once CPAP use stops, the charger would continue to supply just enough current to maintain the battery at 13.7V.


Simple as that.


In reality, in this config or one similar to yours, the IP65 is supplying the majority of the power for the CPAPs while in use. It likely can't keep up only when both are at max power with max heat on the humidifier, BUT by morning, assuming AC power has been available all night, the battery should be at or near fully charged.


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ipyakuza avatar image
ipyakuza answered ·

I received my charger today, updated the FW and did some testing. Yes apparently if you have the mode set to LION and you unplug it, it will remember what mode it was last set for. Picked right back up for LION charging mode which is great. Yeah testing the wattage as noted this does fluctuate between 17-35 watts per CPAP with the humidifier off. The machines are the Respironics System One REMstar Pro and the Philips Respironics DreamStation. I would estimate 2-3 days of 8 hour usage which is more than sufficient. I appreciate the feedback on this. The charger and app are really nice quality compared to a lot of the cheap $20 stuff off Amazon.


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