Batteries Definition and 46 Discussions

A battery is a power source consisting of one or more electrochemical cells with external connections for powering electrical devices such as flashlights, mobile phones, and electric cars. When a battery is supplying electric power, its positive terminal is the cathode and its negative terminal is the anode. The terminal marked negative is the source of electrons that will flow through an external electric circuit to the positive terminal. When a battery is connected to an external electric load, a redox reaction converts high-energy reactants to lower-energy products, and the free-energy difference is delivered to the external circuit as electrical energy. Historically the term "battery" specifically referred to a device composed of multiple cells, however the usage has evolved to include devices composed of a single cell.Primary (single-use or "disposable") batteries are used once and discarded, as the electrode materials are irreversibly changed during discharge; a common example is the alkaline battery used for flashlights and a multitude of portable electronic devices. Secondary (rechargeable) batteries can be discharged and recharged multiple times using an applied electric current; the original composition of the electrodes can be restored by reverse current. Examples include the lead-acid batteries used in vehicles and lithium-ion batteries used for portable electronics such as laptops and mobile phones.
Batteries come in many shapes and sizes, from miniature cells used to power hearing aids and wristwatches to small, thin cells used in smartphones, to large lead acid batteries or lithium-ion batteries in vehicles, and at the largest extreme, huge battery banks the size of rooms that provide standby or emergency power for telephone exchanges and computer data centers.
Batteries have much lower specific energy (energy per unit mass) than common fuels such as gasoline. In automobiles, this is somewhat offset by the higher efficiency of electric motors in converting electrical energy to mechanical work, compared to combustion engines.

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  1. T

    Misc. Looking for entry level DIY ideas

    I'm looking for a way to use these batteries that is safe and also useful. I've looked into buy inverters to turn them into portable battery packs but am out of my depth and don't want to create a device with serious potential fire hazards without thoroughly understanding the ins and outs and...
  2. Dario56

    Internal Resistance of the Battery - Ohmic Resistance

    When current starts flowing in a circuit, voltage of the battery drops from EMF value. There are three sources of this however here I am only interested in ohmic resistance of the battery. EMF of the battery is created because of electrochemical processes on both electrodes which create...
  3. narayan821

    Does DC or AC work best for charging most industrial batteries?

    I have a source of electricity that's alternating but at variable frequencies. So an asynchronous alternating current of sorts if you will. Can industrial rechargeable batteries be charged like this efficiently? Or would DC current work best? Or normal AC?
  4. Kaushik

    Intuition about electromotive force (EMF)

    My understanding of emf Let us consider 2 parallel plates with charges (opp. but equal in magnitude) stored on it. When we connect both the plates from the outer side, the electrons from the lower potential (i.e., negatively charged plate) moves to the higher potential (positively charged plate)...
  5. P

    I Difficult Series Battery Problem

    Modern batteries use double-sided anode and cathodes for greater energy density. Series wiring of batteries is typically accomplished by connecting the anode of one cell to the cathode of another. However, can series be accomplished by stacking double-sided anode and cathode alternatingly with...
  6. Stonestreecty

    I How do I know the lithium content of a lithium-ion battery?

    Power bank is common for our daily life, especially for our smart phone, which always a lithium-ion battery. Taking airplane is easy at our daily life, but there are restrictions on lithium content for air travel, thus air travelers ask the question "How much lithium in a battery am I allowed to...
  7. W

    Electrons @ battery negative terminal

    Does the negative terminal of a battery have a negative charge due to having a surplus of electrons? If so, then why do the surplus electrons from the negative terminal of the battery not discharge to the human body or earth (which have a neutral charge) when touched?....thereby causing the...
  8. SchroedingersLion

    Batteries: Is the current a diffusion current?

    Greetings, I realized that I don't understand a fundamental fact of common Li-ion batteries. During the charging process, electrons are forcefully extracted from the cathode and pushed into the anode. Charge balance then yields a flow of positive Li ions from the cathode to the anode (through...
  9. S

    Battery Charge and Discharge Time Calculations

    I am performing some calculations but struck with confusion whether I am doing it correct or wrong due to contradictions of these calculations on different calculators websites. I hope here someone will help me with the validation of my calculations. Battery Capacity = 150 Ah Battery...
  10. M

    Would a giant orbital gravity battery be a good future power source?

    Gravity batteries intrigue me. We are starting to develop them now. We currently are able to drop cement blocks and harness the energy that the kinetic energy releases. We are considering them as an alternative energy source to help the environment. Here’s a link for those unfamiliar with it...
  11. P

    Would a charged lithium battery combust more energetically?

    Conceptually this question makes sense to me I know a overcharged lithium battery will became unstable however with identical batteries except a different level of charge what would the properties of their combustion be? In depth conceptual, and mechanical explanations are always appreciated as...
  12. Brett Anthony

    Batteries in Parallel, One Reverses Polarity

    So, some time after getting a new car the batteries on my FOB died. So I went in and replaced them, two CR2016's was all that was needed (on top of each other in parallel). No more than a month later I noticed the battery felt like it was dying already (light not as strong, delay on the actions...
  13. R

    Could you create a battery powered plane?

    After watching a video on YouTube, I recently became interested in the dynamics and physic's of why we aren't using electrical powered planes instead of burning thousands of fossil fuels every day. After doing a bit of my own research, I found the problem. When we increase the weight, we have to...
  14. J

    Observed battery set discharge unbalance

    I previously posted the below as a footnote on one my posts on the Mechanical Engineering Forum and it was suggested I start this thread on the subject here. "PS On a general note about battery replacements. On my field GPS I use rechargeable batteries and always test them before recharging...
  15. C

    How to calculate the accurate capacity of a battery?

    I'm trying to figure out how to calculate how much energy is stored in a battery between certain voltages. I know capacity is traditionally calculated by multiplying amps drawn by nominal voltage by time, but this seems like an approximation because voltage decreases as the battery is...
  16. L

    Energy Systems and Optimal Control -- combining energy storage systems like flywheels and batteries

    I'm currently working on combining energy storage systems like flywheels and batteries to balance consumption/regeneration. I've been looking at using an optimal control scheme so that a cost function can be tailored to our wishes. I'm curious about what other people in this field have been...
  17. A

    Are the terminals of a Battery neutral?

    So I've been learning how batteries work. What I learned is that a battery consists of 2 pieces of metal both with different electronegativities. These metals react with an electrolyte. One metal (called the anode) is oxidized and has its electrons removed, leaving behind a positive ion which...
  18. A

    How do Batteries Work?

    So I understand in a battery that an anode (such as zinc) and a cathode (such as carbon) are separated by an electrolyte. I also understand that the electrons want to flow into the cathode, but can't get to them, so as soon as a conductor connects the two terminals, current can flow. However...
  19. T

    In batteries, does stored energy vary with battery voltage?

    Hi For a 1200 watt tool, there are 20, 40 and 60 volt batteries, and in the case of a 2 amp hour (7200 Coulomb) battery, using energy = charge x voltage gives different values of stored energy for each of the three batteries, which are 144000, 288000 and 432000 Joules. Is this correct? Thanks
  20. M

    Can rechargable Li-ion batteries be rebuilt?

    After so many cycles, rechargeable Li-ion batteries powering electric cars go bad. This I know. I am wondering what goes bad? Is it the electrolyte, the electrodes, or both? And in general, could it be possible to take these degraded battery components and fix them? Thanks in Advance! Mike
  21. J

    How much energy is stored in compressed air?

    Hi all, My name is Jesse and I love renewable energy and finding ways of beating coal. Right now Solar Photovoltaic energy competes with coal in sunny areas during the day, but at night, you need to store the energy from solar and it's not worth it due to the cost of storage mechanisms (might...
  22. Mzzed

    Simple Battery Misunderstanding

    If a small voltage - say 1V, is applied to the negative terminal of a 1.5V alkaline battery (although I don't think the type of battery matters?) will this create a current between the 1V and the negative terminal until the charges are somehow balanced? If not, what will this situation do to the...
  23. D

    Engineering Chemical vs Mechanical Engineering

    I am a high school senior caught between these two fields. they both seem very exciting and I am not sure which would be better suited for my interests. In high school, my favorite subjects have been Physics, Chemistry, and Computer Science. I am interested in working to develop: -more...
  24. P

    Find currents I1 and I2 in a 3-loop, 2-battery circuit

    Homework Statement Find currents I1 and I2 in the following circuit: Homework Equations I know I have to use Kirchoff's loop rule but I am not sure of the current going through the 5 ohm and 8 ohm resistors, is it just I1 and I2 respectively? Also do I incorporate the large loop at the...
  25. S

    A Physical Understanding of Kirchhoff's Laws

    < Mentor Note -- thread moved to the EE forum from the Homework forums since it is a more general set of questions > So, we are going into Kirchhoff's Laws in class, and my entire understanding of circuits, which took me a while to form, is again falling apart. A physical understanding is...
  26. T

    Batteries connected in parallel - Amps won´t add up?

    Batteries are connected in parallel. Multimeter shows: 1,5V AND... "0.12A" regardless of battery number. Volts stay the same but should not Amps add up in parallel? "0.12A" with 4, 5 or 6 batteries... Details: Amps measured correctly by closing the circuit with multimeter probes (bulb lights...
  27. G

    Please help me understand how a battery works

    There is an explanation of how a battery works that says that in a battery circuit, the electrons do a complete loop and, given enough time, they can return to their starting point. This theory says that when the electrons arrive in the positive terminal and they lost all of their potential...
  28. A

    I Help with Experiment on Batteries

    Hi guys!! I am currently having Physics Internal Assessment in my school and I want to do an experiment to calculate the different times it takes for a 9V cell to to discharge (reach a 0.1V) in different temperatures. The problem I am having right now is to efficiently discharge my cell. How can...
  29. cyril joel

    Dc motor

    Hello i am abeginer i have to connect a 12v dc motor can i connect it to two 9v batteries in series meabs a total output of 18V.
  30. P

    Charging of a battery

    A battery has an Emf 6 Volts. It is completely discharged. It is charged by maintaining a potential difference of 9 Volts across it. If the internal resistance of the discharged battery is 10 ohms, find the current through the battery, just after the connections are made. My textbook says that...
  31. P

    How to shut off Led on buck converter

    I am using a buck converter with a battery pack, for a usb charger. The issue is, is that the buck converter I have ( http://www.ebay.com/itm/DC-Converter-Step-Down-Buck-Module-7V-24V-to-5V-3A-5V-usb-output-power-adapt-/261030150117?hash=item3cc69bffe5:g:Q3UAAMXQTT9R0Qos ) has a led on it, which...
  32. S

    Charging a battery from a fluctuating, unpredictable source (pedal-powered dynamo)

    So I want to charge a battery from a pedal-powered dynamo, and use that to power my PC, my screen, and pretty much everything else in my home office. This whole thing is a little project to improve my own health while I'm working; I'm not here expecting to make major miracle savings on the...
  33. JordanHood

    Maximum power from a battery with source resistance

    Homework Statement A 5V battery rated at 1800mAh has a soucre resistance of 10 Ohms. What is the maximum power that can be extracted from the battery? Homework Equations The Attempt at a Solution I understand that had the battery not had any source resistance then the power out would have...
  34. C

    Desulfation of batteries

    What are the methods of dissolving sulfate crystals that form on the lead plates in a lead/acid battery?
  35. C

    What happens when we connect 2 batteries + with +, - with -?

    Homework Statement Batteries are connected together with their + and - poles. Homework Equations The Attempt at a Solution I quess that nothing happens because there is no change in potential difference.
  36. Nader AbdlGhani

    Maximum Current Intensity

    Homework Statement How can I get the maximum Current Intensity by connecting 72 cells to a 3 Ohm resistor each cell has a potential difference of 1.5 Volt and internal resistance of 1 Ohm Please don't tell me to connect them all in parallel or all in series as in parallel the potential...
  37. J

    Emulating car battery output through home power?

    I'm setting up an amplifier which is intended for use in a car, and I'm not using it in one. I'm trying to power it through a typical DC 250 volt wall outlet. What kind of transformer should I use? (I'm also trying to power a car stereo with it as well)
  38. ryanuser

    How to store electrical energy?

    Hello I made a little wind turbine so when it is directed at wind it turns and generates electricity as I can see the outcoming voltage on voltmeter. My question is how can I store its energy? Can I use a rechargable battery and let it run out, then stick copper wires at each sides of it coming...
  39. O

    How to hook up a 12-24v system to a battery pack

    I'm working on a very similar issue to the one shown below https://www.physicsforums.com/threads/linking-battery-packs-to-change-voltages-and-how-to-charge.514002/ I've found some batteries that should do the job. i need to keep them fairly small, and the length of charge doesn't matter too...
  40. Vishwas D

    Change in potential of terminals of batteries

    I know there will be potential difference between the terminals of a battery. But when the positive terminal of a battery is connected to the negative terminal of another, will both of the connected terminals achieve the same potential? If so, what happens to the individual potential differences...
  41. CHARLOTTE34

    Connecting a 12v Control panel to a 24v Truck system

    Help! I am connecting a Sergent control panel (to power a motorhome 12v/240v system), with a 1200W converter for a solar panel that trickle charges a 12v battery and a leisure battery. This would not be the problem but my truck runs on 2 batteries that run 24v. Does anyone have an idea on how...
  42. P

    Potential difference across two points in a circuit

    Homework Statement [/B] Find the potential difference between points b and a in the circuit below I have already solved for the voltages of the two batteries (1 and 2) in the circuit (18 V and 7 V respectively) 2. Homework Equations Kirchhoff's Rules 1) Potential difference across any...
  43. D

    Can we store ac power like dc?

    I simply wanted to know, whether we can store AC power like DC?
  44. N

    What is the purpose/function of negative and positive wiring

    This question pertains to all things negative and positive. Such as: batteries, wirings, and atoms. Mainly my confusion comes from the actual purpose. For instance, why does a battery need a negative and positive wire? what function does this serve? why is this distinction of negative and...
  45. Psinter

    Will a high current (3.1A) destroy smartphone battery?

    Will a high current destroy my smartphone battery? I know very little about batteries, but I'm getting really annoyed at having to wait 8 hours for my phone battery to charge (it's a 6 year old smartphone). So I was thinking of raising the 2.1A output of the charger to 3.1A without raising the...
  46. G

    Li-ion discharge rates

    More of a general question but thought I'd post it here. Motorcycles are notorious for losing battery charge and not starting requiring a jump or rolling start. Was looking to get one of these new Li-ion battery / jump start modules capable of starting a car (and charging a phone or tablet)...
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