You didn't mention what your charging energy source was Solar PV, wind, hydro or whatever
But the general concision around here would probably be the Doc Watson
Key Features of "Watt's Up" Mini Power Analyzer:
Measures energy (Wh), charge (Ah), power (W), current (A) and voltage (V) for any rechargeable battery pack from 4 - 60V, including NiCd, NiMH , and SLA, and Li-Ion battery packs
Connector to use a receiver battery for measurement down to 0 V
Captures current peaks and voltage minimums(droops)
Accurate & precise - 0.01 A current and 0.01 V voltage resolutions
Rugged - handles 50 A continuous and 100 A peak at 60 V
14 ga., 7 x 37 stranded, high temp silicone rubber insulated wire without connectors
Small & Light: 2.8" long x 1.7" wide x 0.83" thick (70 mm x 44 mm x 21 mm), 2.5 oz.
Acts like a wire so doesn't affect model's performance. Precision current sensing resistor, with only 0.001 Ohm resistance and circuitry only draws 0.007 Amps
Uses DSP to increase ADC resolution and differential measurement amplifiers to increase noise immunity
Factory calibration stores constants in EEPROM to compensate for component tolerances
One Year Warranty
Complete User Manual
Specifications:
Voltage 0-60 V, resolution 0.01 V. That's a 14 cell series li-poly pack!
Current 0-100 A peak, 50 A continuous, resolution 0.01 A
Charge 0-65 Ah, resolution 0.001 Ah. That's ~32 Amps for two hours!
Power 0-6500 W, resolution 0.1 W. That's ~8.7 Horsepower!
Energy 0-6500 Wh, resolution 0.1 Wh. That's lifting a 50 pound model into outer space (65 mi.)!
Operates from 4.0-60 V, 0 V with optional receiver battery pack
16 x 2 STN LCD display
Powerful, 8 MIPS micro-controlle
Color: Electric Blue
Applications - Specially designed for RC Battery Packs to help you:
Set speed control cutoff voltages and currents
Tune performance by comparing different setups of propeller, motor, gearing, speed control and battery
Measure a full battery charge and compare to spec when charger claims done
Check peak currents are safe for battery, speed control, motor, wiring and connectors
Predict airplane flight time based on ACTUAL conditions in your model
Check battery capacity and health and whether battery should be retired
Verify that the minimum voltage under load is within specifications
Check for wiring and connector power losses.
Fine-tuning your electric RC cars & planes for great performance doesn't have to be a guessing game
Measure power and energy consumption of ANY device with a rechargeable battery pack, such as:
Airsoft gun battery pack
Bike lighting battery pack
E-bike and Scooter battery pack
Combine the power analyzer together with our 2.4V - 7.2V, 7.2V - 12V, 24V NiMH universal smart chargers, and with 3.6V - 14.8V Li-Ion battery charger It is perfect tool to monitor battery pack's performance