12V 20A Battery Charger
A 20A Battery Charger, or 20A Battery Recharger, is a device used to put energy into a secondary cell or rechargeable battery by forcing an electric current through it.
The charging protocol of 20A Battery Charger (how much voltage or current for how long, and what to do when charging is complete, for instance) depends on the size and type of the battery being charged. Some battery types have high tolerance for overcharging (i.e., continued charging after the battery has been fully charged) and can be recharged by connection to a constant voltage source or a constant current source, depending on battery type.
Simple 20A Battery Chargers of this type must be manually disconnected at the end of the charge cycle, and some battery types absolutely require, or may use a timer, to cut off charging current at some fixed time, approximately when charging is complete. Other battery types cannot withstand over-charging, being damaged (reduced capacity, reduced lifetime), over heating or even exploding.
The 20A Battery Charger may have temperature or voltage sensing circuits and a microprocessor controller to safely adjust the charging current and voltage, determine the state of charge, and cut off at the end of charge.
A trickle 20A Battery Charger provides a relatively small amount of current, only enough to counteract self-discharge of a battery that is idle for a long time. Some battery types cannot tolerate trickle charging of any kind; attempts to do so may result in damage. Lithium ion battery cells use a chemistry system which does not permit indefinite trickle charging.
Slow 20A Battery Chargers may take several hours to complete a charge. High-rate 20A Battery Chargers may restore most capacity much faster, but high rate 20A Battery Charger can be more than some battery types can tolerate. Such batteries require active monitoring of the battery to protect it from overcharging. Electric vehicles ideally need high-rate chargers. For public access, installation of such chargers and the distribution support for them is an issue in the proposed adoption of electric cars.
Which electrical practices, and so which charger, are best suited for use depending entirely on the type of battery. NiCd cells must be fully discharged occasionally, or else the battery loses capacity over time due to a phenomenon known as “memory effect.”
Once a month (perhaps once every 30 charges) is sometimes recommended. This extends the life of the battery since memory effect is prevented while avoiding full charge cycles which are known to be hard on all types of dry-cell batteries, eventually resulting in a permanent decrease in battery capacity.
Most modern cell phones, laptops, and most electric vehicles use Lithium-ion batteries. These batteries last longest if the battery is frequently charged; fully discharging the cells will degrade their capacity relatively quickly, but most such batteries are used in equipment which can sense the approach of full discharge and discontinue equipment use.
When stored after charging, lithium battery cells degrade more while fully charged than if they are only 40-50% charged. As with all battery types, degradation also occurs faster at higher temperatures. Degradation in lithium-ion batteries is caused by an increased internal battery resistance often due to cell oxidation.
This decreases the efficiency of the battery, resulting in less net current available to be drawn from the battery. However, if Li-ION cells are discharged below a certain voltage a chemical reaction occurs that make them dangerous if recharged, which is why many such batteries in consumer goods now have an “electronic fuse” that permanently disables them if the voltage falls below a set level. The electronic fuse circuitry draws a small amount of current from the battery, which means that if a laptop battery is left for a long time without charging it, and with a very low initial state of charge, the battery may be permanently destroyed.
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