please help me to understand why voltage is added in battery in series

[monmalmi]

please help me understand why voltage is added in battery in series ,and why battery in series not discharge each other because postive is connected to negative,thanks

[Doctorandus_P]

The best way to learn is by doing, and this is among the simplest electrical experiments you can do. So grab yourself a few batteries and a volt meter and start connecting it in various way.

If you have 1.5V batteries (such as AA sized Alkaline)  and a 6V light bulb, or a LED with series resistor (100 Ohm will do) then you can also see the result of connecting batteries in series.

[Zero999]

Just connecting two batteries in series doesn't cause them to discharge, because a complete circuit is required for current to flow and discharge the batteries.

[Mr. Scram]

please help me understand why voltage is added in battery in series ,and why battery in series not discharge each other because postive is connected to negative,thanks

Consider that voltage is always the relative potential between two points. This means voltages aren't absolute, but relative to whatever you're measuring against. So if you stack two batteries and put your common lead on the negative pole of the second battery you get the following.

                                        N
                                         |
(3V) +==-  (1.5V)  +==- (0V)

But if you put the common load in the middle you get the following.

                      N
                       |
(1.5V) +==-  (0V)  +==- (-1.5V)

Both are true, because the measurements are relative. It just depends on between which two points you measure. Now you'll hopefully understand you're stacking potential and why they are effectively added up.

[monmalmi]

but my question is when you put battery in series we connect positive of one battery to the negative to the other battery then why they not discharge each other

[ArthurDent]

As others have said, if one battery is 1.5 volt, 2 in series measured from the negative of the first one is 3 volts. Ignoring the slow discharge caused by time and temperature, for those batteries to discharge you need to have a circuit that will allow the current from the positive on the top battery to flow to the negative of the bottom battery. Think of a two cell flashlight with an incandescent lamp. the lamp must be rated 3 volts because the voltages add. When the flashlight is off the batteries will last a very long time (called shelf life) because there is no load or circuit to complete the return path to the negative of the first battery. If you turn the flashlight on and leave it, the batteries will discharge fairly quickly because you have created a discharge path through the lamp.

[monmalmi]

i understand all of that but when we add batteries in series we connect the metal postive pole of one battery to metal negative pole of then second battery then why they not discharger each other as negative is connected to positive ?

[janoc]

Zero999 has answered that above.

For the batteries to discharge, the current needs to flow. And for a current to flow there has to be a  closed circuit, which you don't have.

I guess you are getting confused by the negative to positive pole bit - but keep in mind that voltage is relative (as others explained above), it depends on what you are measuring it against. The positive/negative only makes sense relative to the other pole of the same cell. Once you add another cell, it doesn't matter - a + end of one cell could well be negative relative to the other one (or vice versa).

It is not like with fire and water that when you put fire with water together they will always destroy each other. With voltage we are only speaking about relative potentials, not some absolute qualities.

[Domagoj T]

You must understand that voltage is potential difference, and that the + side of the battery is 1,5V above the - side of that same battery. That is it, nothing more. Notice that this says nothing about the difference in potential between + side of one battery and - side of some other battery. Until you connect them, there is no relation whatsoever between the two.
At the moment you connect them a common potential is established, but since they are in direct short circuit, the difference of that potential is 0, which means you can add together the individual voltages on the far side of the series connection (-1,5V and +1,5V ) for a total of 3V difference.

[Mr. Scram]

i understand all of that but when we add batteries in series we connect the metal postive pole of one battery to metal negative pole of then second battery then why they not discharger each other as negative is connected to positive ?

Because you're still assuming voltages are absolute. If both batteries would have an absolute and universal value of 0V at one end and 1,5V at the other, then they would discharge each other. But there isn't some universal standard of voltage levels like there is for temperature. There simple is a potential of 1,5V between the two ends. Whether you interpret that as 10V and 11,5V or 0V and 1,5 V is completely arbitrary. Both are equally valid

Maybe it's a little bit easier if you just look at one battery. If you put the input lead on the positive terminal and the common lead on the negative, you'll see a voltage of around 1,5V. That's the potential between those two points. What happens if you switch each lead to the other terminal?

[Brumby]

i understand all of that but when we add batteries in series we connect the metal postive pole of one battery to metal negative pole of then second battery then why they not discharger each other as negative is connected to positive ?

Because the positive of one battery is connected to the negative of a DIFFERENT battery.  It doesn't work the way you are thinking when it's a different battery.

As said above, current only flows when there is a circuit - a loop around which electricity can flow.  When you connect the positive to the negative of the SAME battery, you get such a loop.  It you start from the positive terminal, then travel along whatever you used to connect the positive to the negative, then go into the negative terminal and through the battery back to the positive.  This makes a closed loop - a circuit - and current will flow.

When you connect the positive of one battery to the negative of the other (and nothing else) there is no way for current to pass through either battery.  You have to make a loop - and only things that are within a loop will have current flow.


The thing to understand is that a battery does not create electrons - it merely provides the energy to push electrons through a conductor.  It can't absorb electrons either - it just uses the same electrons (in the battery and the circuit) over and over, recycling them.  This is why there must be a loop, so the electrons can be recycled.

[Zero999]

When the positive and negative of two different batteries is connected together, no current flows, because the circuit is incomplete. In order for current to flow, the other positive and negative terminals also need to be connected together.