I monitored a battery discharge and recharge cycle on a Samsung 500T to get a feel on how it can be a better partner in my mini solar system. Right now it is constantly plugged in to the lead-acid battery array, leaving its own internal battery constantly full. I want to make use of that battery capacity to help store solar power for the 500T's current task of displaying ESA's space station tracker.

For this first draft I want to avoid cracking the computer open, which means I don't have any control over the charging algorithm. It will charge at full speed whenever I connect power, and it will try to charge to 100%. Charging to full is stressful for lithium ion batteries and decreases their lifespan. Some computers offer the ability to halt charging at 80% reducing use of capacity in exchange for extending the usable life of the battery. Unfortunately I saw no such option with the 500T.

The discharge rate is also pretty much fixed, as I've turned off all I can of Windows and Samsung crapware. Leaving just the ISS tracker and Node-RED running. About the only parameter I can adjust is the rate at which Node-RED queried data, and I think I can back off from once per minute to maybe once per three or five minutes. This will help a tiny bit.

The good news is that, watching through the data retrieved by Node-RED through a discharge and charge cycle, I see nothing worrisome about that data and willing to trust it. With data in hand, there are two more things to bring in to the picture: (1) a switch for the tablet's power cord to my lead acid batteries, and (2) a program to connect/disconnect that power at the best times to optimize the system. I want to think over the latter before I spend money on the former.