TakeTheActive
Enlightened
The Welcome Mat thread, with the thrust of it being the opening post, written and maintained by TigerhawkT3, and reflecting suggestions from the member input of the replies contained in the thread, was inadvertently lost.
An archival copy of that important post, is reprinted here:
My archival copy of my suggested revision to two answers is below:
Thanks for all the varied info. While I understand basic electricity and batteries, LED flashlights are 'new' to me. LOTs to come back to and read more!
Regarding 'Basic Electricity', I disagree with your answer to the following question (Voltage is not pipe size - that's Resistance; Voltage is pressure. C is not current - it's current available over a period of time) and offer an alternative:
Originally Posted by
A: That's not a question, but okay.
Think of Amps as the amount of water flowing through a pipe.
Think of Resistance as the diameter of a pipe. A large diameter pipe will allow MANY gallons per hour to flow through it, while a smaller diameter pipe will resist the flow and pass less. [Example: The water company runs a 12" line down the center of your street (for everyone). They run a 1" line to your house (your MAXIMUM water flow). After the water meter, the plumber runs a 3/4" line to the center of your basement and then taps off 1/2" lines to the various faucets. Changing back to 1" at the end of a 1/2" run will NOT increase the flow since it's already been restricted by the 1/2" run. Poor connections between your battery and your LED will restrict the flow of current.]
Think of Watts as total WORK done. A large diameter pipe with water flowing through it at a low pressure (really slowly) will fill a bucket in the same amount of time as a small diameter pipe with water flowing through it at a high pressure (blasting through it - like when you put that 'Water Rake' attachment on the end of your garden hose to clean your driveway). This is why high-voltage applications are preferred over high-current applications, as a stream of water zooming at 200mph through a 1"-diameter pipe is much more dangerous and difficult to maintain than a calm, 3mph flow of water through a 4'-diameter pipe.
As for Capacity, that's just a function of current draw and time (milliamps per hour; gallons per hour). Any power source discharged at a 1C rate will be depleted in 1 hour (draw 2000mA from a 2000mAh cell). Any power source discharged at a .25C (or C/4) rate will be depleted in 4 hours (draw 500mA from a 2000mAh cell), and so on. As an example, a 1.8Ah AA NiMH capable of an excellent 10C discharge rate can manage 1.8*10=18 amps.
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I also offer an alternate, possibly clearer, answer for this question:
A: Series connections have the LOAD connected to the first cell's positive terminal and the last cell's negative terminal. The individual cells are then connected, END-to-END, positive-to-negative. An example is the Classic Maglite, or your grandfather's incandescent 2XD flashlight. This arrangment ADDs up the Voltages of the cells (2xAA: 2.4VDC) but can only supply the Capacity of the smallest / weakest cell. (That's why MATCHING cells is so important).
Parallel connections have all of the individual cells positive terminals connected together and all of the individual cells negative terminals connected together. The LOAD is then connected to the common positive junction and the common negative junction. This arrangment ADDs up the Capacities of the cells (2xAA @ 2000mAh: 4000mAh) but at the Voltage of a single cell. (You only connect identical Voltage cells together!). An example is those 3AA>1D adapters where all three AA cells' positive terminals meet at the top, and all their negative terminals meet at the bottom. Such a configuration has the same voltage as a single cell, but can handle a higher current draw (or the same current draw for a longer amount of time).
For example, 1AA alk can push about 500mA at around 1.5V for about four hours. 2AA alks in series can push 500mA at around 3V for about four hours. 2AA alks in parallel can push 1000mA at around 1.5V for about four hours (or 500mA for eight hours, and so on).
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I hope you find them useful.
An archival copy of that important post, is reprinted here:
My archival copy of my suggested revision to two answers is below:
__________________________________________________
Thanks for all the varied info. While I understand basic electricity and batteries, LED flashlights are 'new' to me. LOTs to come back to and read more!
Regarding 'Basic Electricity', I disagree with your answer to the following question (Voltage is not pipe size - that's Resistance; Voltage is pressure. C is not current - it's current available over a period of time) and offer an alternative:
Originally Posted by
Q: Please explain V)olts, A)mps, R)esistance, W)atts, and C)apacity.TigerhawkT3 said:
A: That's not a question, but okay.
- Volts are electrical potential.
- Amps are electrical current.
- Resistance, measured in Ohms, is the opposition offered by a body or substance to the passage through it of a steady electric current.
- Watts are total power, the product of Volts times Amps.
- Capacity, expressed in mAh, is the amount of electrical current available over a period of time.
Think of Amps as the amount of water flowing through a pipe.
Think of Resistance as the diameter of a pipe. A large diameter pipe will allow MANY gallons per hour to flow through it, while a smaller diameter pipe will resist the flow and pass less. [Example: The water company runs a 12" line down the center of your street (for everyone). They run a 1" line to your house (your MAXIMUM water flow). After the water meter, the plumber runs a 3/4" line to the center of your basement and then taps off 1/2" lines to the various faucets. Changing back to 1" at the end of a 1/2" run will NOT increase the flow since it's already been restricted by the 1/2" run. Poor connections between your battery and your LED will restrict the flow of current.]
Think of Watts as total WORK done. A large diameter pipe with water flowing through it at a low pressure (really slowly) will fill a bucket in the same amount of time as a small diameter pipe with water flowing through it at a high pressure (blasting through it - like when you put that 'Water Rake' attachment on the end of your garden hose to clean your driveway). This is why high-voltage applications are preferred over high-current applications, as a stream of water zooming at 200mph through a 1"-diameter pipe is much more dangerous and difficult to maintain than a calm, 3mph flow of water through a 4'-diameter pipe.
As for Capacity, that's just a function of current draw and time (milliamps per hour; gallons per hour). Any power source discharged at a 1C rate will be depleted in 1 hour (draw 2000mA from a 2000mAh cell). Any power source discharged at a .25C (or C/4) rate will be depleted in 4 hours (draw 500mA from a 2000mAh cell), and so on. As an example, a 1.8Ah AA NiMH capable of an excellent 10C discharge rate can manage 1.8*10=18 amps.
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I also offer an alternate, possibly clearer, answer for this question:
Q: What are series and parallel?TigerhawkT3 said:
A: Series connections have the LOAD connected to the first cell's positive terminal and the last cell's negative terminal. The individual cells are then connected, END-to-END, positive-to-negative. An example is the Classic Maglite, or your grandfather's incandescent 2XD flashlight. This arrangment ADDs up the Voltages of the cells (2xAA: 2.4VDC) but can only supply the Capacity of the smallest / weakest cell. (That's why MATCHING cells is so important).
Parallel connections have all of the individual cells positive terminals connected together and all of the individual cells negative terminals connected together. The LOAD is then connected to the common positive junction and the common negative junction. This arrangment ADDs up the Capacities of the cells (2xAA @ 2000mAh: 4000mAh) but at the Voltage of a single cell. (You only connect identical Voltage cells together!). An example is those 3AA>1D adapters where all three AA cells' positive terminals meet at the top, and all their negative terminals meet at the bottom. Such a configuration has the same voltage as a single cell, but can handle a higher current draw (or the same current draw for a longer amount of time).
For example, 1AA alk can push about 500mA at around 1.5V for about four hours. 2AA alks in series can push 500mA at around 3V for about four hours. 2AA alks in parallel can push 1000mA at around 1.5V for about four hours (or 500mA for eight hours, and so on).
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I hope you find them useful.
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