Lately there has been a few threads on how to measure solar charge, battery condition, State of Charge etc.
I purchased a meter on eBay from a mob called elite.element. Does everything I want it to day plus more . Cost was about $30. Complete kit apart from a bit of hook-up cable. Easy to install (even for me!!). Just back from a short 2 week trip and it was a good piece of kit. Instructions are in Chinglish but easy to understand.
It can measure Forward and Reverse current.
Combines many functions in one,
Dual display for Voltage (V)
Current (A), Power (W)
Ampere-hour (Ah),
Working Hours (H), Charging Time, Discharging Time
Battery capacity (%)
Have built-in shunt, no need external shunt,
Flexible On-line calibration function, calibrate Voltage and amps reading easily.
Adopting modular design, collocate indicator lights on the panel for various working status.
4 digits LED for Voltage, Power, and Working hours reading, 3 digits LED for Current and Ah reading.
Lowe power consumption.
External power supply DC12V/24V, or powered by the same source being measured (10-90V).