NiMH battery charger

The charging method for NiMH (nickel-metal hydride) & NiCD batteries mainly adopts a “2-stage” process of "high C.C. main stage + low C.C. trickle stage". In fact, during the first stage, which is the high constant current main charge stage (usually 0.2~2C), the battery is already 100% charged. The role of the subsequent low C.C. trickle charge (usually 0.01~0.03C) is to prevent the self-discharge of nickel-metal hydride batteries. Determining when to end the high current main charge is quite challenging. Unlike lead-acid or lithium batteries, which rely on the battery voltage rising to a certain fixed value for judgment, the peak voltage of nickel-metal hydride batteries during the charging process is not a fixed value. Moreover, this value will slightly decrease as the battery becomes fully charged, a phenomenon known as the -dV (negative voltage change) phenomenon. The -dV phenomenon is unique to nickel-metal hydride and nickel-cadmium batteries during charging and is not observed in lead-acid or lithium batteries. Our NiMH battery chargers are all equipped with detection circuits that accurately capture this -dV. The charger mainly ends the high current main charge phase based on the appearance of this -dV and automatically switches to the trickle charge phase.

1.Charging Process:  
       1.The right graph is the charging curve of the NiMH charger, with black representing voltage and red representing current. The voltage curve within the circle illustrates the -dV phenomenon (the voltage slightly drops after reaching its peak). Since the -dV of nickel-metal hydride batteries is quite small, typically only 3~6mV for a single cell, the charger's detection function must be of high precision and low noise, requiring a high-precision, low-noise digital detection circuit for support.

                                   

2.Charging status display:
       Our chargers offer three types of charging display methods. The basic model is using a RED/GREEN bi-color LED to indicate the charging status. For customers who need to know the state of charge (SOC) at any time, they can choose our chargers with Fuel Gauge LEDs indicator.

3.Safety protections:
       3.Safety is a critical aspect of NIMH battery chargers. Mian of our battery chargers provide protections against overvoltage, undervoltage, overcurrent, overtemperature, short-circuit, battery reversed conditions.

4.EMC & LVD approval:
       All of our battery chargers passed basic EMC & LVD safety approval requirements. Many chargers have CE, CB, FCC, CCC, ETL, PSE, UKCA, cTUVus, SAA, KC and RCM.