This is an intermediate DIY project that is great for determining 12V lead acid battery AH capacity up to 127 Ah. Suitable for batteries found in road vehicles, military, marine, UPS and avionics.
The attached zip contains all the instructions, schematics and microcontroller code to get it working. the BOM is in the Battery Load Sample document. There is an ICSP programming header built on the PCB for convenient code flashing.
AH Capacity tester-update.rar
Auto Ah Capacity Tester & Logger for 12V lead acid Batteries
Safe, autonomous Ah capacity testing with auto shutdown & recharge option.