Product Information

The B250 series charger is portable AC or DC powered battery charger. It is an intelligent charger incorporating new technology allowing it to charge both Ni-cad and Ni-Mh type batteries using a wide range of bespoke AC adapters to accommodate most of the worlds power requirements. The unit can also be powered from a DC source with an input range of 10-30V.

The chargers can be used in workshop, vehicle and field applications. This is a fast-charge battery charger with conditioning and uses a switch-mode current regulator to charge the battery and features a pulsed trickle charge. Fast-charge termination is accomplished by five methods: negative voltage change, positive temperature change, maximum temperature, maximum time and maximum voltage.

AC Input

An AC adapter is supplied 230VAC 50Hz UK style Part Number BPSU type 961014. (Note - alternative chargers are available for different country requirements and are issued a different type number to identify them).

DC Input

The unit has a DC input range of 10 - 30 Volts; an optional DC lead is available BPSU type DCLEAD1. (Note - alternative DC input leads are available for different requirements and are allocated a different type number).

Charge Detection Methods

Charge Pending

Before fast-charge is initiated, the battery voltage must be above 8 volts and the temperature between 10 and 50°C. If the voltage and temperature is outside these limits the charger will be in a "charge-pending" state and will only supply a trickle charge.

Fast-Charge

Fast charge is normally initiated by applying power to the charger or by battery replacement. If the voltage of the battery is below 8 volts the charger will wait until the trickle current brings the voltage up before fast-charge is initiated. The charging rate is set at 240mA and has a conditioning feature for Ni-cad batteries.

Trickle-Charge

This provides a pulsed trickle charge, on for 1 second in every 2 second period.

A trickle charge is applied to the battery after fast-charge has terminated to compensate for self-discharge.

Fast-Charge Termination

Negative voltage change: When maximum charge is reached the terminal voltage of Ni-Cad batteries declines significantly, so this charger samples the battery voltage every 1 second and compares it to all of the previous values. If the new value is less than any of the previous values by more than 120mV, a negative delta voltage has been detected and fast-charge is terminated.

Temperature Rise

When the internal temperature of the battery increases by more than 1.25°C in 5 minutes the fast charge is terminated. This termination technique is rarely utilised when charging Ni-Cad batteries since negative delta is usually detected before this temperature increase. This temperature rise termination is essential when charging Metal Hydride Mi-Hd batteries as the negative delta voltage is not as pronounced as in the Ni-Cad batteries.

Maximum temperature termination: This is used as a safety net to prevent problems, and should never be needed under normal operation of the charger. The NTC thermistor values are shown below. Termination occurs when the NTC falls below +10°C and above +50°C.

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