Good afternoon Bruce,
I also have a CPAP with humidifier I am concerned most about. It is expensive to replace and is one of the other reasons I was looking the just protect the whole DC block. I found out after the fact this has been a problem for years on the fans. My fans have been working flawlessly up until now and the only thing that has changed was after the 2nd round of charging the pair of batteries back up to full from where the BMS cut them off (27.5%/13.02v to 14.1V/599.8AH).
Other than running fans on speed 2 or 3 and LED lights on occasion there was no other battery usage (charger still on to keep them topped off). Then a few days later I was checking the AiLi Voltmeter to check status of things and noticed some Boost charging was going on and saw it flash 14.4 then to 14.6 before it started going down. I unplugged the charger so I could try to figure out why the boost was happening when battery was full the night before. That is when I started having he erratic behavior with my front fan (rear was is fine as near as I can tell, both the same age).
I have replaced the control board with the "supposed" upgrade for Lifepo4 but that quit yesterday. Prior to installing the new control board I tested the fan motor just to make sure it was working; it worked no problems at all. Now, after installation of the new control board and running fan a few days it quits working again. I test the motor again and now it is burned out or at least not working where it was working before. It is not a power problem; there is power all the way to the fan (typically around 13.7v, same as the dc fuse block).
I did a random test out of curiosity; I unplugged the charger and attached the multi-meter to it just to see how much it shows when first plugged in...13.2 then 13.6 then 14.4 and back down to 13.6 all within a matter of a few seconds. I found this info online for the PD9260CV charger: "The Boost Mode rapidly charges the batteries at 14.4 volts till the batteries reach 90% charged. The Normal Mode finishes the charge cycle by reducing the voltage to 13.6 volts till the batteries are done charging. Once the battery is completely charged the unit switches to the Storage Mode and maintains the batteries at 13.2 volts.
The Equalization Mode charges at 14.4 volts every 21 hours for 15 minutes to prevent battery stratification and sulfation."
The last sentence (every 21 hours...) is what I am wondering is affecting the fans. I leave my fans running 24/7 usually one doing intake the other exhaust. If I end up putting individual buck converters on do you have any recommendations on them or at least which ones to stay away from? Some of the reviews I have read on some are not so great. My apologies for this being so long.
Thank you for your input!
Harry