"Oz....you lost me with the calorie thing
Is that 18 watts going into the battery every second??
If thats right then you also have to add the 3 lights that are lit at the same time.....artv "
I think we need to distinguish between energy and power or joules and watts, so you can see the difference.
If we were to take a hand grenade, we may find about 150 grams of tnt inside. We know it goes bang, and is deadly, and appears to release a lot of energy.... but does it really.
1 gram of TNT is worth about 4kilo joules of energy.. so 1 grenade stores about 150x4= 600 kilo joules of energy.
1 gram of chocolate is worth about 22kilo joules of energy... so 150 grams of chocky stores about 150x22=3300 kilo joules of energy.
So 150 grams of chocolate is over 5 times the energy of the grenade..... but you don't explode when you eat it.... why not?
Well power is energy expended over time. If we expend it very quickly like the grenade, we develop a lot of power for a very short time.
With the chocolate, we use a much larger amount of energy over a longer time.... small power for long time.
It is the same with capacitors, we can discharge them quickly or slowly. The energy will be the same, but the power will be completely different.
A practical example
I build low impedance electric fencing units sometimes, and we charge up a 50 uf capacitor to 600v and then release the energy into the primary of a transformer very very quickly via a SCR..... lets look at the figures.
The joules will be (50uf capacitor) 1/2 x .000050 x 600^2 or about 9 joules.
When I measure the output on the secondary, we find about 40 amps@8000volts using the fence tester into a load.
If voltsxamps=watts then 40x8000=320000 watts.... and that includes the transformer and switching losses.
So we know how much power it put out, but over what time did this happen..... well if a watt= joule per second, then it follows that joules/watts= time so 9/320000=.000028 seconds... or 28 millionths of a second.
It is actually faster than that, as the transformer is saturated to hell, and pulled our output watts down considerably, so in reality, it is probably closer to a 10 millionth of a second..... but you can see that we put out probably close to half a million watts for about 10 millionths of a second in reality.
If we were to discharge that same capacitor over a 1 second period, the power would be 9 watts.... big difference... just like the grenade and the chocolate.
So you must get these two concepts separated into what they really mean. I hope this helps do that with a real world example.
I mentioned calories as your from USA. We use joules, I thought you would be more familiar with calories.
From a practical standpoint, 1 calorie can heat up 1cc of water 1 degree Celsius. that small c calorie is equal to 4.2 joules. The big C calorie is 1000 small calories, or 4.2kj. If your wife diets she will be familiar with the big C calorie.
I don't know how fast your capacitor is discharging into your battery, so I can't give you your wattage. The 18 watts was just a simple example.
Is the mud any clearer...
.................oztules
