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<blockquote data-quote="helotaxi" data-source="post: 7110619" data-attributes="member: 550915">The energy in a battery is not stored in an electric field between two plates but rather in a chemical form.&nbsp; That makes a big difference in how it stores and more importantly releases the energy that it stores.&nbsp; Hook a cap up to a voltage source of, say, 18V.&nbsp; Let the voltage stabilize and then disconnect the source.&nbsp; Wait a few minutes and check to voltage on the cap.&nbsp; It will be right at 18V.&nbsp; Try the same thing with a car battery and it will settle out back around 12.8-13.4V depending on the battery.&nbsp; Plot the voltage of a cap under a constant load with no additional charge being provided and you will find that it is pretty much a straight line.&nbsp; Do the same with a battery and you will see that it is a very shallow slope until it gets to around 10V at which point it falls off a cliff.&nbsp; Hardly linear.&nbsp; It can maintain a higher voltage over a higher range of loads and over a longer period of time.&nbsp; The energy in a cap is stored over the entire range of voltage from working voltage to 0V.&nbsp; A battery, on the other hand, has its usable energy above 10V and is capable of maintaining over 12V under discharge for a good deal of time.The lights are going to dim under a load regardless because the inductance of the alternator does not allow it to react instantly.&nbsp; It becomes less obvious with a battery bank because the skin voltage on the batteries dampens rate of voltage drop making it a more gradual drop rather than a flicker.&nbsp; The flicker is what the eye is sensitive to.&nbsp; I still don&#039;t see what&#039;s so hard to understand about the fact that pulling 100A for 0.1sec is the same amount of stored energy that much be replaced whether that is from one battery or from 100 batteries.&nbsp; It&#039;s 10 amp-seconds of energy any way you pull it.&nbsp; It&#039;s all about the area under the curve.&nbsp; Take the integral of the current plotted over time, divide by the time lapsed.&nbsp; If the result is less than the alternator output (minus car systems) then your alternator is actually sufficient for your system.&nbsp; If you have some really big peaks in there, a couple of batteries will keep the voltage higher.&nbsp; The ESR on a battery isn&#039;t nearly as high as you seem to think that it is and by wiring several of them in parallel, you&#039;ve decreased the effective ESR even further.&nbsp; Lower ESR means that the battery bank can deiliver a higher voltage over an even longer period of time and under an even higher draw.</blockquote>

[QUOTE="helotaxi, post: 7110619, member: 550915"] The energy in a battery is not stored in an electric field between two plates but rather in a chemical form. That makes a big difference in how it stores and more importantly releases the energy that it stores. Hook a cap up to a voltage source of, say, 18V. Let the voltage stabilize and then disconnect the source. Wait a few minutes and check to voltage on the cap. It will be right at 18V. Try the same thing with a car battery and it will settle out back around 12.8-13.4V depending on the battery. Plot the voltage of a cap under a constant load with no additional charge being provided and you will find that it is pretty much a straight line. Do the same with a battery and you will see that it is a very shallow slope until it gets to around 10V at which point it falls off a cliff. Hardly linear. It can maintain a higher voltage over a higher range of loads and over a longer period of time. The energy in a cap is stored over the entire range of voltage from working voltage to 0V. A battery, on the other hand, has its usable energy above 10V and is capable of maintaining over 12V under discharge for a good deal of time. The lights are going to dim under a load regardless because the inductance of the alternator does not allow it to react instantly. It becomes less obvious with a battery bank because the skin voltage on the batteries dampens rate of voltage drop making it a more gradual drop rather than a flicker. The flicker is what the eye is sensitive to. I still don't see what's so hard to understand about the fact that pulling 100A for 0.1sec is the same amount of stored energy that much be replaced whether that is from one battery or from 100 batteries. It's 10 amp-seconds of energy any way you pull it. It's all about the area under the curve. Take the integral of the current plotted over time, divide by the time lapsed. If the result is less than the alternator output (minus car systems) then your alternator is actually sufficient for your system. If you have some really big peaks in there, a couple of batteries will keep the voltage higher. The ESR on a battery isn't nearly as high as you seem to think that it is and by wiring several of them in parallel, you've decreased the effective ESR even further. Lower ESR means that the battery bank can deiliver a higher voltage over an even longer period of time and under an even higher draw. [/QUOTE]

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