How to convert VA to Watts and KVA to Kilowatts?
Since watts is volts times amps, what is VA? VA (or volt-amps) is also volts times amps, the concept however has been extended to AC power. For DC current
VA = Watts (DC current).
In AC if the volts and amps are in phase (for example a resistive load) then the equation is also
VA=Watts (resistive load)
where V is the RMS voltage and A the RMS amperage.
In AC the volts and amps are not always in phase (meaning that the peak of the voltage curve is does not happen at the peak of the current curve). So in AC, if the volts and amps are not precisely in phase you have to calculate the watts by multiplying the volts times the amps at each moment in time and take the average over time. The ratio between the VA (i.e. rms volts time rms amps) is called the power factor PF.
VA·PF = Watts (any load, including inductive loads)
1. What is Lithium Polymer C rating?
A lot of radio-control fliers quickly grasp the meaning of most of the battery-associated acronyms but one: the C rating. In fact, many experts have tripped over themselves trying to explain it. However, I've heard a graspable explanation of it from an old Chinese battery manufacturer/expert very recently. Which is: The "C Rating" is the number which you multiply to the capacity of the battery to get its discharge rate.
Still confused? Basically, a 1000 mAh battery rated at 1C will provide 1000 mA of power for 1 hour. On the other hand, if the same pack was rated at 2C, it would provide 2000 mA of power for 30 minutes.
2. How fast can I charge a Li-Polymer pack?
Each Lithium Polymer battery pack has a different maximum charge rate. It is very important to never ever charge at a rating above the specified rate! Most batteries have a label that specifies this vital information. However, if the maximum charge rate is not specified, keep in mind that most Lipos are made to be charged at a rate of 1C. Which means a 1000 mAh pack can be charged at 1A and a 500mAh pack can be charged at 0.5A. Once again, never ever exceed the maximum charge rate lest the battery explodes!
What is trickle charge? Theoretically a trickle charge is a charge rate that is high enough to keep a battery fully charged, but low enough to avoid overcharging. Maintenance charge is another way to describe trickle charge. Determining the optimum trickle charge rate for a particular battery is a bit tricky to describe but is generally accepted to be around ten percent of the battery capacity - i. e. Tenergy 2500 mAh AA NiMH optimum trickle charge rate is at or below 260mA. One of the reasons it is important for you to understand the optimum trickle charge rate for your charger and batteries is to compensate for the self discharge of NiCD and NiMH batteries. Another reason is because overcharging a battery will definitely reduce its useful life. Although most manufacturers do not recommend that you leave a battery in the charger for long periods of time, many people leave their batteries in the charger on trickle charge for days or weeks to keep their batteries "ready to use". If you know the rate of trickle charge that your charger puts out and it is around one tenth of the battery capacity or less, then you should be alright if you are just going to do this occasionally. Generally speaking, though you do not want to leave a battery charger plugged in unattended for long periods of time. Is trickle charging harmful to batteries? Many battery manufacturers do not recommend long term ( months at a time) trickle charging. If trickle charging is used then the charge rate should be very low or only intermittent. The best smart chargers will only send an occasional pulse charge to the battery once it is charged. They do not apply a continuous low rate of charge. Some battery resellers state that applying a continuous trickle charge of about 1/10th the battery's capacity is not harmful. However, we have not seen any battery manufacturer condone the practice. It is better to fully charge batteries and then store them fully charged in the freezer than to leave them on trickle charge for very extended periods of time.
Quick charging NiMH batteries will reduce their life. For practical purposes with batteries that are designed to be quick charged, for example, Sanyo, GP, that is not true. It is important to use a battery charger that has been specifically designed to rapid charge NiMH cells. Actually there is a much greater likely hood of reducing the life of a NiMH battery by using an "overnight" charger than by using a smart fast charger. Overnight chargers rely on the fact that you will unplug them after a number of hours. If you forget to unplug them they can continue to charge the batteries longer than they should. Overcharging WILL reduce the life of batteries. From a strictly technical sense, a battery that is always slow charged will likely last a little longer than one that is always rapid charged. However, the difference is so small that it is not likely to be noticeable for most users. A battery with a capacity of 2,800 mAh can deliver a current of 2,800 mA for an hour Assigning capacities to batteries can be very tricky, that's probably why you don't see capacity ratings marked on most alkaline batteries. When powering high drain electronic devices like digital cameras, computer peripherals, or portable music players, an alkaline battery will only deliver a small fraction of its rated capacity. A NiMH or NiCd battery is likely to deliver much closer to its rated capacity when it's powering high drain devices. This means that a NiMH battery with a rated capacity of 1800 mAh can take many more photos than an alkaline battery with a rated capacity of 2,800 mAh.
How to convert Watts to Amps? You cannot convert watts to amps, since watts are power and amps are coulombs per second If you have at least least two of the following three: amps, volts and watts then the missing one can be calculated. Since watts are amps multiplied by volts, there is a simple relationship between them. However, In some engineering disciplines the volts are more or less fixed, for example in house wiring, automotive wiring, or telephone wiring. In these limited fields they often have charts that relate amps to watts and this has confused people. What these charts should be titled is "conversion of amps to watts at a fixed voltage of 110 volts" or "conversion of watts to amps at 13.8 volts," etc. The Following Equations can be used to convert beween amps, volts, and watts. Converting Watts to Amps The conversion of Watts to Amps is governed by the equation Amps = Watts/Volts For example 12 watts/12 volts = 1 amp Converting Amps to Watts The conversion of Amps to Watts is governed by the equation Watts = Amps x Volts For example 1 amp * 110 volts = 110 watts Converting Watts to Volts The conversion of Watts to Volts is governed by the equation Volts = Watts/Amps For example 100 watts/10 amps = 10 volts Converting Volts to Watts The conversion of Volts to Watts is governed by the equation Watts = Amps x Volts For example 1.5 amps * 12 volts = 18 watts Converting Volts to Amps at fixed wattage The conversion of Volts to Amps is governed by the equations Amps = Watts/Volts For example 120 watts/110 volts = 1.09 amps Converting Amps to Volts at fixed wattage The conversion of Amps to Volts is governed by the equation Volts = Watts/Amps For Example, 48 watts / 12 Amps = 4 Volts
It's best to recharge batteries slowly? Quick charging NiMH batteries will reduce their life.? Not true. For practical purposes with batteries that are designed to be quick charged, for example, Sanyo, GP, Tenergy, that is not true. It is important to use a battery charger that has been specifically designed to rapid charge NiMH cells. Actually there is a much greater likely hood of reducing the life of a NiMH battery by using an "overnight" charger than by using a smart fast charger. Overnight chargers rely on the fact that you will unplug them after a number of hours. If you forget to unplug them they can continue to charge the batteries longer than they should. Overcharging WILL reduce the life of batteries. From a strictly technical sense, a battery that is always slow charged will likely last a little longer than one that is always rapid charged. However, the difference is so small that it is not likely to be noticeable for most users.
Light Measurement*: Your light is bright as H*** or it's not, that is the best measurement. All light measurements can be traced back to the Candela, which is the unit of luminous intensity. The Candela is also sometimes called candlepower, and is similar to an older unit, the candle, which was based upon an actual candle of specified dimensions and construction. There are two basic methods used by various flashlight manufacturers to rate the light output of their products. Total Luminous Output may be expressed in candela or in lumens. This is a measure of the entire light output of the flashlight regardless of beam focus. It is almost solely a function of the lamp, and for practical purposes is equal to the lamp output which lamp manufacturers rate in Mean Spherical Candela (Sometimes called Mean Spherical Candlepower which is not the same as peak beam candlepower), or in lumens. Multiply candela by 12.57 to convert to lumens. For example, the 20 watt lamp used in the SL-35X is rated at 450 lumens or 35.8 Mean Spherical Candela.
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