I have recently moved from my still good, 8 year old K2 to the rated 9 amp version of these PowerSonic Iron Phosphate batteries:

https://www.power-sonic.com/batterie...etooth-series/

I am very happy with it so far. My tester shows that at a 1 amp discharge rate I'm getting 10.3 Amp Hours. The battery has over/under voltage protection although I have not tested the feature. The app (Android only) is very useful providing SOC, voltage, current measurement in/out, number of discharge cycles, individual cell voltage readings, and battery use event errors (over/under voltage, etc.) It works great. I am able to insure that starting the flight I'm at 100% SOC (well, 99% because I know that my charger slightly undercharges.) After 5 hours of use I'm down to 60% very consistently. The Bluetooth system is TI-based and I believe that the BMU is also TI-based. It is a tremendous value for what you get.

Danny Brotto