Types of Battery Chargers:
Simple or Manual Battery Chargers: This type of chargers connects to a constant DC power source and uses a small current to gently charge batteries. They are generally slow and since they do not alter their output based on time, the user has to manually stop charging by cutting off the power supply. A 2000mAh NiMH battery may take up to 36 hours to be fully charged with this type of chargers, but this longer charge duration can be useful to avoid over-charging. Simple battery chargers are also inexpensive but quite effective.
IC Timer Controlled Battery Chargers: IC just stands for Integrated Circuit, in which timing is monitored by a silicon chip. Timer batter chargers has the same output similar to simple chargers but they charge in less than half the time of manual chargers and output is ceased after a pre-determined time. However, they are not suitable for top-up charging and they may overcharge because they can�t determine the initial of batteries. This means that if a battery has already been fully or partially charged, IC timer controlled battery chargers will still try and charge batteries for the full duration of its timer. In order to combat this complication, some of them have �overcharge protection� sensors.
Intelligent or Microprocessor Controlled Battery Chargers: When a specific voltage is reached, a microprocessor controlled battery charger is able to determine when to stop fast charging and then �trickle charges� the battery. Not only that, it also monitors temperature and time under charge to determine the optimum charge current at that instant. This implies that batteries in any charge state can be fully charged in less then about 3 hours without risk of overcharging, because termination of the charging is based on the combination of the voltage, temperature and time indication. Microprocessor controlled battery chargers are the latest, safest and most efficient battery chargers today.
Fast Charging and Top Up Charging:
�Fast charging� refers to the rapid charging of batteries fully, usually within one to three hours. This may result in shortened life or reduced capacity if current is not controlled. �Top up charging� means charging a re-chargeable battery before it has been completely discharged.
Trickle Charging:
�Trickle Charging� refers to a very slow rate of charging in order to keep fully charged batteries at their maximum energy level, which prevents overcharging. Battery capacity between 1/30 and 1/20 Milli-Amp-Hour (mAh) are considered to be �trickle currents� in which for a 1600 mAh battery, for example, 50 and 80 mA is measured to be suitable. All newer battery charger models use this �trickle charging� system which allows for a safer and more efficient battery charging.
Delta V + T Control:
�Delta V control� refers to a method in which the charger automatically detects when a battery is fully charged. This method controls and monitors when the charger is supposed to stop fast charging and switch to trickle charging mode. �Delta T control� on the other hand monitors battery temperature and controls charging depending on the temperature profile. Both these methods require full microprocessor control, and are capable of "topping-up" partially discharged batteries.
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