Chargers for NiMH and NiCd
The NiMH rechargeable battery has become a popular technology for mobile energy in recent years, due to its constantly increasing power density and economical price.
There are various possibilities for charging Nickel Metal Hydride or Nickel-Cadmium batteries.
Standard charging technology
Trickle chargers are the most basic type and supply a low power continuous charge to the battery with no automatic cut off. They are designed so that the charging current reduces as the cell voltage increases, so offering some degree of charging control at a cost effective price.
Timer chargers have an automatic pre-set timer that is set according to the capacity of the batteries to charge and the fast charging current of the charger. When the pre-set time is reached, the charger switches from fast charge to a slow top-up or trickle charge. This trickle charge will keep the battery at full capacity without the risk of overcharging. A timer charger will charge the batteries with the same amount of energy, regardless of the state of discharge of the batteries at the start of the charging process.
–∆V charging technology
The most commonly used processor controlled charging method is the –∆V method. The cells will be optimally charged regardless of their energy level at the beginning of the charging process without overcharging. Using this technique a very short charging time is possible.
The increase of the cell’s voltage is monitored by a microcontroller. After the cells have reached their end-charging voltage, the cell voltage decreases by a few millivolts. This characteristic (–∆V), which is seen in both NiCd and NiMH cells, is used to detect when the cells are fully charged. The charger then automatically switches to trickle charge mode to keep the cells topped up and compensate for their self discharging.
For controlling the charging process it is very important to detect the –∆V very accurately. ANSMANN’s industrial systems benefit from the vast experience that the company has in the consumer charger market. More than a million chargers have been produced and sold within the last 15 years and they are recognised for their high quality level.
Customised solutions
Customised solutions can be integrated into the customer’s application. Charging cradles with integrated charging electronics can also be offered.
All ANSMANN NiMH and NiCd standard intelligent chargers use the –∆V technology. In addition these chargers have a safety timer and, as an option, can include temperature control or a discharge function.
For lower priced alternatives, customised timer and trickle chargers can be provided.
