Series or parallel

ico

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For example: when using a light that uses 2 AA batteries, let's make the fenix E21 as example light, the batteries inside make a series connection right? IT also means that the voltage increases but the capacity stays the same. So the total voltage will be 2.4V(1.2 * 2) but the capacity will still only be 2000mAh using eneloops. If the light consumes 1000mah, the light would run for 2 hours. If I also use a light that only takes 1 AA and consumes 1000mAh, that light will also run for 2 hours.

Why is it that some lights, lets say a given of 200 lumen output with 2AA for 2 hours while adding an AA extender will make it 3 hours(made up but close to what others say in their catalog). The addition of the other battery will only increase the total voltage but the 2000mAh capacity remains right? what does adding another battery make so that the light will run longer? Does it lessen the consumption of milliamps?

And for the parallel type, linking to battery would double the capacity and make the voltage same right? so 2 eneloops connected parallel will have an operating voltage of 1.2 and a capacity of 4000mAH?
 

Th232

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You're mixing up amperage with power (and power over time with instantaneous power for that matter).

Using your numbers, two Eneloops in series will essentially be a battery with a voltage of 2.4V and 2000 mAh as you've said. Total energy is 2.4 * 2 = 4.8 watt-hours, i.e. it can nominally provide 4.8 watts for 1 hour, or 1 watt for 4.8 hours.

The LED requires a certain amount of power to run, note that I say power as it will require a voltage as well as a current. The E21 will convert the power input from the battery to the right voltage and current. If the LED draws 1000 mA (NOT mAh) it'll require somewhere around 3.6 V. Using Ohm's Law this translates to 3.6 W. Therefore it'll theoretically run for about 1.33 hours (practically it'll run for less). Again using Ohm's Law, when the batteries are still both at 1.2 V for a total of 2.4 V, they'll be drawing 1.5 A.

If you add a third battery, you now have a battery pack with 3.6 V and 2000 mAh. Note that the total energy has increased to 7.2 watt-hours. Running through the same calculations again, you'll find that the current draw at the batteries will now be reduced to 1 A. Theoretically it'll run for two hours.

And yes, two Eneloops in parallel would result in 1.2 V and 4000 mAh.
 

ico

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Don't really know most thing about electronics as it is far from finance. :drool:

I did understand most, if not some, of your explanations though. thank you
 

Mr Happy

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Don't really know most thing about electronics as it is far from finance. :drool:

Electronics is not far from finance. Think of a battery as a deposit account with a certain amount of electricity (money) deposited in it. A battery of a certain size holds a certain amount of electricity. It's like a deposit account with a maximum limit on the funds you can deposit. So if you have one battery, you have so much stored electricity. If you have two batteries, you can have twice as much electricity. Just the same with money, if you had one deposit account with the maximum balance you would have so much money. If you had two deposit accounts filled up you would have twice as much money. With three batteries or three deposit accounts you would have three times as much.

Now consider you spend money at a certain rate. Similarly, lights use electricity at a certain rate. So if you had two deposit accounts at maximum balance you could spend money for twice as long before you ran out as if you had one account only. Three accounts or three batteries would let you go three times as long. Of course if you had three accounts but you spent money three times as fast, you would not last any longer. This is just the same as having a more powerful light. If it uses electricity three times as fast in order to produce three times as much light, then it will burn through three batteries just as fast as a small light burns through one battery.
 

Wrend

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That analogy, while true to an extent, isn't exactly fitting (depending how you look at it, I suppose).

In a series battery setup, the electrons from one cell flow into the next and so on until you get to the main circuit, then the last cell's electrons flow through the circuit and into the first cell. Adding cells in series does not increase the amount of electrons that flow through the circuit. Adding them in parallel does.

Of course you need enough voltage to overcome the resistance in the circuit to move enough of the electrons to be able to do enough work in the first place. In a regulated flashlight, it will drain enough current to be able to do enough of the work (provided the source power is within operational limits). So when the source voltage is higher, it basically doesn't need to drain as much current to do the same amount of work.
 
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Mr Happy

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That analogy, while true to an extent, isn't exactly fitting (depending how you look at it, I suppose).

In a series battery setup, the electrons from one cell flow into the next and so on until you get to the main circuit, then the last cell's electrons flow through the circuit and into the first cell. Adding cells in series does not increase the amount of electrons that flow through the circuit. Adding them in parallel does.

Of course you need enough voltage to overcome the resistance in the circuit to move enough of the electrons to be able to do enough work in the first place. In a regulated flashlight, it will drain enough current to be able to do enough of the work (provided the source power is within operational limits). So when the source voltage is higher, it basically doesn't need to drain as much current to do the same amount of work.

You have to view electricity as "electrical energy" not electrons. A certain amount of electricity allows a certain amount of work to be performed, just a certain amount of money allows a certain amount of stuff to be purchased.

If you drain your bank accounts in series, then you empty one account first and then you empty the second one. If you drain your bank accounts in parallel, then you drain both accounts at the same time, a bit of one and a bit of the other. Either way it's the same amount of money and the same amount of goods purchased.

Likewise, whether you put your batteries in series or in parallel it is the same amount of electrical energy stored, and potentially the same amount of work done.
 

ico

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Electronics is not far from finance. Think of a battery as a deposit account with a certain amount of electricity (money) deposited in it. A battery of a certain size holds a certain amount of electricity. It's like a deposit account with a maximum limit on the funds you can deposit. So if you have one battery, you have so much stored electricity. If you have two batteries, you can have twice as much electricity. Just the same with money, if you had one deposit account with the maximum balance you would have so much money. If you had two deposit accounts filled up you would have twice as much money. With three batteries or three deposit accounts you would have three times as much.

Now consider you spend money at a certain rate. Similarly, lights use electricity at a certain rate. So if you had two deposit accounts at maximum balance you could spend money for twice as long before you ran out as if you had one account only. Three accounts or three batteries would let you go three times as long. Of course if you had three accounts but you spent money three times as fast, you would not last any longer. This is just the same as having a more powerful light. If it uses electricity three times as fast in order to produce three times as much light, then it will burn through three batteries just as fast as a small light burns through one battery.

I didnt say I dont know anything about it, just said don't know most.

I know that part somehow that is why I gave my own explanation in the first part. Th232, then explained that I was limiting my answers to voltage and mAh 's that's why I wasn't able to figure out how the battery system works.

I thought that the battery just consumes the mAh( like your money analogy). that is why I thought that a 2AA connected in series which has a 2000mAh will just burn up as quickly as a 3AA connected in series since in also holds 2000mAh. But I was wrong.
 

MarioJP

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Well in series doesn't that increases the workload per amount of energy stored?? more volts means more watts in the same amount of "stored energy"?? that's like having "interests rates" added to your account. Something tells me this is not the right analogy I think lol.
 
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ico

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If you drain your bank accounts in series, then you empty one account first and then you empty the second one. If you drain your bank accounts in parallel, then you drain both accounts at the same time, a bit of one and a bit of the other. Either way it's the same amount of money and the same amount of goods purchased.

So with your explanation, does it mean that with a 2AA light; the milliamps stored in the first cell is first depleted before 2nd cell does?
 

Mr Happy

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So with your explanation, does it mean that with a 2AA light; the milliamps stored in the first cell is first depleted before 2nd cell does?

No it doesn't mean that. It just means that two batteries contain twice as much electricity as one battery. Whether you connect them in series or in parallel, two batteries are still twice as much as one battery.
 

ico

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but you just said that if an account is linked likea series connection, the first account would be depleted first before the 2nd one.

I know what you mean by the doubling of the amount but it really is not the same.

Please stop the analogies with banks and stuff as it is not doing any better. It would be much better if you explained all the things you said a while ago using the real deal, talk with batteries and all and not use the bank or deposits as it is really not that the same.
 
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Mr Happy

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but you just said that if an account is linked likea series connection, the first account would be depleted first before the 2nd one.

I know what you mean by the doubling of the amount but it really is not the same.

Please stop the analogies with banks and stuff as it is not doing any better. It would be much better if you explained all the things you said a while ago using the real deal, talk with batteries and all and not use the bank or deposits as it is really not that the same.

Well, OK, but it is very difficult to begin without understanding that everything in science is fundamentally about accounting. Accounting for mass, accounting for energy, accounting for atoms, accounting for electrical charge. Everything always has to balance. Any entry you add in a credit column of a balance sheet must have an equivalent entry in a debit column.

Once you have the concept of accounting, then you consider how fast things flow or move around and which path they take.
 

trevordurden

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I'm not a genius when it comes to electronics but this is my theory so far

In a basic unregulated circuit:
batteries in parallel will double the capacity while keeping the voltage the same
batteries in series will double the voltage while keeping the capacity the same

However, in regulated circuit
The flashlight will limit the output so if there is twice as much voltage, it won't need as much current draw and draw less current to keep the same output.

I've only come up with this theory from my observations, and if someone has a better understanding, please feel free to prove me wrong.
 

Wrend

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Yes, the current rate isn't constant. It depends on the resistance of the circuit and the source voltage as well. In effect, in a regulated or otherwise controlled circuit, the resistance isn't a constant either and changes according to what the circuit needs (within certain limitations). Perhaps this is adding to the confusion. Some cells and packs are rated to a certain healthy current limit, but this doesn't mean that that is how much they will necessarily push through the circuit, or that they can't push more through and overheat or cause other problems if given the opportunity.
 

yellow

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I think You do not want us now to show You the formulas, so I will try an easier approach:

You already got that series an parallel correct:
when placing cells in series, the voltage goes up,
when placing cells parallel side by side, the mAh go up, the voltage stays the same.

Now You have Your 2*AA light: inside there is a driver that changes the energy taken from the cells to what the led needs.

short:
with 2 cells the light "needs" a certain current.
when You use only one cell, the driver "misses" one cell and has to take more current from the remaining one
when You add one cell (3 instead of 2), the driver does not need to take the same current and thus - with reducing the power taken from the 3 cells - can give a longer runtime.


Think of this and when You want, I can give You the basic formulas
(it really is easy, when one has gotten the 1st context correctly)
;)
 

ico

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A formula would be better.
Actually, I asked this question without saying I wanted an easy answer. A somehow difficult to understand but accurate answer would be much better than comparing oranges with apples.

Bring the formulas on yellow:naughty:

thanks
 
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HKJ

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I will not give you any formulas, but some curves:
ThruNite%20TN11%20High.png

In this chart the red curve is the current and as can be seen the current will change with the voltage. At 12 volt it is about 1 ampere (4xCR123 batteries), but at 6 volt it is about 2 ampere (2xCR123), i.e. the light uses double the current with two cells, reducing the runtime to less than half. The brightness (green line) is nearly horizontal, i.e. the light has about the same brightness at both 6 and 12 volt.

Note: a CR123 batteries is not really 3 volt when under load, it is lower.
 
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