Are there any FOSS alternatives for AccuBattery / Battery Guru?

Android provides this information natively under /sys. Exactly where depends on your version.

But if you want an app, merely searching F-Droid for "battery" produces a number of leads.

Theres batterybot and batterybot pro, but those dont do nearly what accubattery does. I use batterybot pro to give me notifications at 80% and 30% so i can unplug at 80 and charge at 30 to keep the cycle counr down. Since i am only charging/discharging 50% it only does half a cycle at a time and keeps it from either extreme.