series battery

Thread Starter

TheSpArK505

Joined Sep 25, 2013
122
Greetings everyone, hope you all good and healthy.

I'm studying series cells in a battery and came to the point where I couldn't click on the physics of the series cells connection. I mean I can easily apply
KVL and conclude the voltages add up. However, I couldn't understand the physics, like what does it mean for voltages to add up ?

would anyone please explain. photo attached below.

Thanks a lot.
 

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Delta prime

Joined Nov 15, 2019
329
I mean I can easily apply
KVL and conclude the voltages add up. However, I couldn't understand the physics
inside the battery, charge is transported by ions in the electrolyte. The chemical reactions of the electrolyte with the anode & cathode materials remove electrons from one and add electrons to the other
Excess electrons are unstable and want to fill in atoms that can accept electrons. Excess electrons are loaded in the negative side of a battery and stored because the electrolyte will not allow them to the positive side where they can be accepted. There has to be a conductor between the neg and pos to allow them to flow or they will stay there, stored until they leak out slowly and there is no longer a potential (difference) between the two. When you add two batteries in series the potentials (voltage) are added because since the same charge is moved twice each time thru the same voltage (potential) the total work done is 2 * V but the current flow remains the same. In Parallel, the charge is moved once through either battery so the voltages of the batteries are not added but with two batteries, the charge can do twice the movement because both batteries allow twice the movement and so the currents are doubled. Kind of like a river and dam. Each battery is a wall of a certain height (potential) and the water is the current flow. Each battery (wall) can only allow so much water to go through. The main large river split into two rivers with a dam on each allows twice the water (current) through at the same water height (Voltage). Whereas if you stack the dams up then they only will allow the same amount of water as one dam and the water will be double the height (voltage). And each dam (battery) only has so much water to provide and must be connected back to the empty portion of the dam because it is a sealed water system so water can’t flow unless water comes back. The empty portion of the dam is lower (positive terminal) and thus can collect water but can’t re-run it through the system unless it is pumped (charged) back up to the higher portion of the dam (negative terminal
 

Thread Starter

TheSpArK505

Joined Sep 25, 2013
122
Each battery is a wall of a certain height (potential) and the water is the current flow. Each battery (wall) can only allow so much water to go through. The main large river split into two rivers with a dam on each allows twice the water (current) through at the same water height (Voltage).
How come if the large river is split into two each dam (battery) can supply twice the flow !! I believe each dam should supply half the large river's flow, don't you think ?

I know you used the river as an example to illustrate how the connections work and I really appreciate it. However you missed me on the above point, please explain.

Thanks a lot.
 

Delta prime

Joined Nov 15, 2019
329
Let's try this again without the analog of a river and Dams.
When you connect two identical batteries in parallel, you double the output capacity while keep the output voltage the same as either battery. In the other case, if two identical batteries are connected in series, the output voltage is doubled but the output capacity is kept the same as either battery.
The positive and negative terminals of a battery are connected to two different types of metal plates, known as electrodes, which are immersed in chemicals inside the battery. The chemicals react with the metals, causing excess electrons to build up on the negative electrode (the metal plate connected to the negative battery terminal) and producing a shortage of electrons on the positive electrode (the metal plate connected to the positive battery terminal).
The difference in the number of electrons between the positive and negative terminals creates the force known as voltage. This force wants to even out the teams, so to speak, by pushing the excess electrons from the negative electrode to the positive electrode. But the chemicals inside the battery act like a roadblock and prevent the electrons from traveling between the electrodes. If there’s an alternate path that allows the electrons to travel freely from the negative electrode to the positive electrode, the force (voltage) will succeed in pushing the electrons along that path.
When you connect a battery to a circuit, you provide that alternate path for the electrons to follow. So the excess electrons flow out of the battery via the negative terminal, through the circuit, and back into the battery via the positive terminal. That flow of electrons is the electric current that delivers energy to your circuit.
As electrons flow through a circuit, the chemicals inside the battery continue to react with the metals, excess electrons keep building up on the negative electrode, and electrons keep flowing to try to even things up as long as there’s a complete path for the current. If you keep the battery connected in a circuit for a long time, eventually all the chemicals inside the battery are used up and the battery dies (it no longer supplies electrical energy):cool:
 

Thread Starter

TheSpArK505

Joined Sep 25, 2013
122
Thanks for the reply, and sorry to reply this late.
you mentioned that chemicals in the electrolyte block current flow through the shortest path" the electrolyte it's self". Can you please explain which part of the electrolyte does that exactly. For example, H2SO4, it decomposes to positive H2 ions that react with anode to leave out access electrons. While SO4 negative ions interact with cathode to make it more positive( less free electrons). Hence the potential difference develops, So please Help me with the following points:
1. Why doesn't battery runs out of electricity quickly since all the components( electrodes and electrolyte) ready to react with each others immediately even before the load connected. Is it because the rate of reaction happening is really slow ?

2. so once chemical reaction happens (no load yet), there is a potential difference exist between the anode and cathode right? why don't they equalize by current moving through the "neutral" electrolyte ?


Thanks in advance.
 

Audioguru again

Joined Oct 21, 2019
1,473
A battery will run out of electricity quickly if you short it. But then the current and heating are so high that the battery might explode or catch on fire.
 

Thread Starter

TheSpArK505

Joined Sep 25, 2013
122
A battery will run out of electricity quickly if you short it. But then the current and heating are so high that the battery might explode or catch on fire.
I'm not saying shorting it. I'm saying whether electricity can flow through the electrolyte if no load is connected to the terminals of the battery.
 

Audioguru again

Joined Oct 21, 2019
1,473
I'm not saying shorting it. I'm saying whether electricity can flow through the electrolyte if no load is connected to the terminals of the battery.
A battery produces current when it has a load. Its electrolyte is not a load.
Energizer guarantees that its alkaline battery will last for 10 years if not loaded, then it will work fine but maybe not as powerful as when new.
 

Thread Starter

TheSpArK505

Joined Sep 25, 2013
122
A battery produces current when it has a load. Its electrolyte is not a load.
Energizer guarantees that its alkaline battery will last for 10 years if not loaded, then it will work fine but maybe not as powerful as when new.
I mean why doesn't current flow through the electrolyte, isn't it ionic. PS. current flows through the electrolyte when a load is connected.
 

Audioguru again

Joined Oct 21, 2019
1,473
Who cares when and if current flows in the electrolyte of a battery.
Simply, a battery lasts a long time when it is not loaded and its chemicals are used up when it is loaded.
 
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