For more information, please visit .
A good charger provides the base for well-performing and durable batteries. In a price-competitive market chargers often receive low priority. The battery and charger must go together like horse and carriage (Figure 1), and this is not always the case. Engineers are often not fully aware of the complex power requirement of a portable device and the need to charge under adverse conditions.
Figure 1: Battery and charger must go together like horse and carriageChargers are divided into personal and industrial, “smart” and “dumb,” slow, fast and ultra-fast types. Consumer products come with a low-cost personal charger that performs well when used as directed. The industrial charger is often made by a third party and includes special features, such as charging at adverse temperatures. Although batteries operate below freezing, not all chemistries can be charged when cold and most Li-ion falls into this category. Lead and nickel-based batteries accept charge but at a lower rate.
Some Li-ion chargers (Cadex) include a wake-up feature, or “boost,” to allow recharging if a Li-ion battery have fallen asleep due to over-discharge. A sleep condition can occur when storing the battery in a discharged state and the self-discharge brings the voltage to the cut-off point. A regular charger treats such a battery as unserviceable and the packs are discarded. Boost applies a small charge current to raise the voltage to between 2.20 and 2.90V/cell and activate the protection circuit, at which point a normal charge commences. Caution applies if Li-ion has dwelled below 1.5V/cell for a week or longer.
Lead- and lithium-based chargers operate on Constant Current Constant Voltage (CCCV) by which the voltage is capped when reaching a set limit. At this point of the charge cycle, the battery begins to saturate and the current drops. Full-charge occurs when the current drops to a set level. Lead acid requires a periodic full saturation to prevent sulfation.
Nickel-based batteries charge with constant current and the voltage is allowed to fluctuate freely. This can be compared to lifting a weight with an elastic band where the hand moves ahead of the load. Full charge detection occurs when observing a slight voltage drop after a steady rise. This method is known as the Delta Voltage Delta Temperature (DVDT) and works well with rapid and fast charge. To safeguard against anomalies, such as shorted or mismatched cells, the charger should include a plateau timer to terminate charge if no voltage delta is measured, as well as a temperature sensors.
A temperature rise is normal with nickel-based batteries, especially when reaching the 70 percent charge level. The reason for this is a decrease in charge efficiency and the charge current should be lowered to limit stress. When “ready,” the battery must cool down. If the temperature stays above ambient, then the charger is not performing right and the battery should be removed. Extended trickle charge on nickel-based batteries inflicts damage. NiCd and NiMH should not be left in the charger unattended for weeks and months. If not required, store them in a cool place and apply a charge before engagement.
Lithium-based should always stay cool on charge. Discontinue using the battery and/or charger if the battery heats up on charge. Li ion cannot absorb over-charge and therefore does not receive trickle charge when full. It is not necessary to remove Li-ion from the charger, however, if not used for a week or more, it is always best to place the pack in a cool place and recharge before use.
The most basic charger is the overnight charger, also known as slow charger. This goes back to the old nickel-cadmium days where a simple charger applied a fixed charge of about 0.1C (one-tenth of the rated capacity) as long as the battery was connected. Slow chargers have no full-charge detection; the charge stays engaged and a full charge of an empty battery takes 14–16 hours. When fully charged, the slow charger keeps NiCd lukewarm to the touch. Because of its reduced ability to absorb over-charge, NiMH should not be charged on a slow charger. Low-cost consumer chargers to charge C AA and AAA cells often use this charger method, so do some children’s toys.
The rapid charger falls between the slow and fast charger and is used in consumer products. The charge time of an empty pack is 3–6. When full, the charger switches to “ready.” Most rapid chargers include temperature sensing to safely charge a faulty battery.
The fast charger offers several advantages and the obvious one is shorter charge times. Short charge times demand tighter communication between the charger and battery. At a charge rate of 1C, which the fast charger typically uses, an empty NiCd and NiMH charges in a little more than an hour. As the battery approaches full charge, some nickel-based chargers reduce the current to adjust to the lower charge acceptance. The fully charged battery switches to trickle charge, also known as maintenance charge. Most of today’s nickel-based chargers have a reduced trickle charge to also accommodate NiMH.
Li-ion charges are most efficient and charge the battery to 70 percent in less than an hour. The extra time is devoted for the long saturation charge that is not mandatory as it is for lead acid. In fact, it is better not to fully charge Li-ion as it will last longer. Of all chargers, the Li-ion charger is the most simplistic. No trickery applies to improve battery performance and longevity. Only the CCCV method works.
Lead acid cannot be fast-charged and the term “fast-charge” is a misnomer. Most lead acid chargers charge the battery in 14–16 hours; anything slower is a compromise. Lead acid can be charged to 70 percent in about eight hours; the all-important saturation charge takes up the remaining time. A partial charge is fine provided the lead acid occasionally receives a fully saturated charge to prevent sulfation.
Yes, having a universal charger is surely more convenient - just like the fact you have the same voltage in every outlet in the region is more convenient that having a city divided into districts where some districts have 127 volts and others have 220 volts and outlets look uniform (that actually was in use in some cities in Soviet Union in the past).
The number one reason why there's no universal charger is manufacturers being greedy. Having a charger unique to a brand and/or model range lets them sell those chargers at a premium. For example, Nokia sells a 1280 phone with a battery and a charger for about 27 bucks in my region but a separate charger is sold for about 20 bucks. And if I attempt to use a third-party charger my phone warranty is deemed void. If third-party chargers were allowed this would be impossible.
The number two reason is this gives extra flexibility to the phone manufacturer. Should they decide to produce a phone that charges faster (say one hour) they have to supply it with a charger capable of such fast charging and such charger will usually be larger and heavier that a slower charger. Also if you use a charger that outputs less power with a phone that requires more power charging takes longer and that's not very convenient. When the manufacturer selects and locks you into the charger they can provide better user experience at expense of requiring you to use exactly the right charger.
Currently you can enjoy "universal" chargers if your device can charge via USB (micro-USB or any other variety). Since USB is a standard it doesn't matter if you plug your device into a charger with a USB connector or into a powered USB computer port. So there're no means for the device to know where the USB port resides.
The company is the world’s best galvanized steel wire rope company supplier. We are your one-stop shop for all needs. Our staff are highly-specialized and will help you find the product you need.