This morning I woke up to a dead iPad battery. I had to do some tax work for the business so I decided I might as well use the opportunity to connect my iPad Air to the Pentametric Battery Monitoring System and track how much energy it used to charge from 0% to 100% SOC.
For this first test I chose to run the iPad through a small 400W inverter off a 12V battery bank. I chose this method because it is the most popular way I see customers charging iPads. It is NOT the most efficient way!!
Later on in this article you will see that I also tested 0-100% charging via a 12V USB adapter. Suffice it to say it is much more efficient than using the inverter.
The battery bank was LiFePO4 so the voltage remained well over 13.3V for the entire duration. This could potentially make the inverter operate a tad more efficiently, but we are talking peanuts..
For this test the iPad was asleep except for the few seconds I opened it to snap a shot of the state of charge (SOC). This may not be representative of how you use one on a boat but we charge ours at night and while they are asleep.
Battery Bank - 400Ah LiFePO4
Inverter - 400W Cobra MSW
iPad Power Supply - Apple 2.4A 120V to USB Adapter
Charging Cable - Apple Brand USB to Lightning
iPad - Asleep and all apps closed
Tracking Equipment - Bogart Engineering Pentametric Monitoring System With USB102 Interface