What is a battery?


New Member
Hi Grit
Yes, water analogy is the ideal way to explain many electrical terms, it is the way I always explain.
I hope I have not offended anyone by commenting on what is an obvious error & certainly not trying denigrate what I considered a very good post on both batteries & ohms law .
I believe this is an open forum??


4x4 Earth Contributer
Hi Grit. I really enjoyed our debate. You also need to be commended for your polite and proper manner in putting forward your points of view. I need to make sure I get my facts right before I go off preaching about Ohm's Law and other things. As explained below I found out today that globes are not really very Ohmic! That was probably part of the problem in our discussion.

And oldrtack123, thanks for your contributions. No offence taken at all. Thats what these forums are all about. Its great that we can have our disagreements, learn from others, and put up with being a little peeved at times about what we thought we knew might not be as sound as it could have been. We can all learn a lot more before we go toes up. And the great thing about it is that it’s all for free!

Some interesting info about the applications of those light bulbs to ballast circuits, and how they also used a resistor to stop expensive bulbs from blowing. I think there is a resistor used in a similar way in the ignition circuit of cars? Have seen it referred to at times but have not got round to looking up the circuit diagrams to check it properly.

Yes, my memory has let me down on how non-Ohmic a bulb really is ( a low voltage bulb ). I have stated that "A light bulb has a fairly constant resistance. ( But not perfectly Ohmic - i.e. its resistance actually increases a little as the current increases", and "A light bulb filament does increase its resistance, but as far as I can remember from some of our classroom experiments over the years I do not recall the increase being too large."

So having the equipment close at hand I thought why not take a few measurements to find out what does happen as the voltage and current increases. Just how Ohmic / non-ohmic are these small bulbs. The bulbs I used were rated at 2.5V 0.3A. Here are the results for measuring V and I for 1, 2, 3 and finally 4 cells in series, and the calculations of resistance;

V(Volts), I(Amp), R(Ohms)
Cold (no current), 1.3
1.2, 0.46, 2.6
2.13, 0.64, 3.3
3.22 , 0.77, 4.2
4.02, 0.90, 4.5

So, yes, there is quite an increase in the resistance as the filament heats up. Not even close to Ohmic as the resistance rises from 1.3 ( cold ) to 4.5 ohms.

I found the specification values of 2.5V 0.3A interesting. When you work out the resistance using these values you get about 8 Ohms! Much greater than anything I measured. So how do you interpret that? Maybe it means that you should not apply more than 2.5 Volts, or more than 0.3 Amps for optimal performance and life. They are probably a rating rather than a specification of actual performance. By that I mean they are not actually saying that if you apply a voltage of 2.5V the current will be 0.3A .

I don’t know if anyone is interested, but I will see if I can work out how to attach a file, and if I can I will post the Year 9 notes I use on Series and Parallel Circuits and their water analogies – plus the questions!
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New Member
A battery is a collection of one or more cells contained within a single unit.

Thanks Grit, perhaps I should have used a ;)
I agree, it is a great example of two intelligent people having a difference of opinion without having an argument. Thanks for a stimulating discussion.


4x4 Earth Contributer
Here are those notes on the Water Analogy I use with my Year 9 students. I think most of them get the simple water analogy pretty easily, especially with the series circuits, but many have a bit of trouble using it with the parallel circuit diagrams. The main thing is it stretches those brain cells and makes them think. A few of them really catch on quickly, and hopefully enjoy their new found skill. With a bit of luck some of them might find a career as an electrician or in the electronics industries.


  • Water Analogy.zip
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New Member
Hi Millsy
Millsy said
"I found the specification values of 2.5V 0.3A interesting. When you work out the resistance using these values you get about 8 Ohms! Much greater than anything I measured. So how do you interpret that? Maybe it means that you should not apply more than 2.5 Volts"
I will have to do some checking on that one but it will probably be a while before I come back, a pretty serious health problem with daughter will have my undivided attention for some time .


4x4 Earth Contributer
Thanks oldetrack123. Sorry to here the bad news about your daughter. Wish her the best from us on the forum. We will be thinking of her, and yourself and family, and hoping she gets up and going as good as ever, as quick as possible.

Thanks also for that bit about the 60W house bulb. If not for that info I would not have thought to just go and spend 10 minutes in the lab and get the facts, rather than waffling on. All the best, Millsy.


Well-Known Member
I'd love to get to get GRIT and me ol mate MILLSY around a campfire! Couple of beers each, and slip in a VALIUM! Could make for a hilarious night!!:rolleyes: It would be like a slow motion headbutting comp! Onya lads, keep up the good work!!:D hehehehe:D


Okay Frosty, lets not bring goats into this! :p

The reason it may have seemed a bit like watching paint dry is that I usually just have this forum and several others running in background as I spend way too many hours working at this computer. Often, by the time I get to actually reading something & responding, most have called it a day.

I guess in the case of this particular thread it was similar to on-line chess, where each player gets but a small window of time each day to see which piece was moved and respond by repositioning your pieces. <in-joke>

It made for an excellent digression from the chores at hand & it would be quite an honour to catch up with Millsy for a beer by the camp-fire some time.
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New Member
i need help in getting a new deep cycle battery,my bond brand battery died exactly to the day,the warranty ran out..........not happy.


On a more serious note everyone is wrong. This is how a battery really works

And now I reveal a well kept secret - everything you always wanted to know about electricity.

Forget all that nonsense about magnetic fields and the flow of electrons along a conductor, for it is just that, a myth put about by auto electricians to support their lavish lifestyle at your expense. The reality is ...smoke! When you think about it all becomes startlingly obvious - smoke makes all electrical things function. If smoke escapes, the component stops working. For example, the last time you had to grovel under the car to replace the starter motor, didn’t it start smoking before it ceased working? Of course!

The wiring loom in your car carries smoke from one device to another, pumped around the system by the dynamo, and when a wire springs a leak it lets all the smoke out and everything stops. The starter motor requires lots of smoke to work properly so it has a very thick wire going to it. The battery stores up lots of smoke dissolved in the battery acid, which is why they were once called accumulators, until it became apparent that we unwashed home mechanics would twig to the secret. Naturally. if you try to, dissolve too much smoke in your battery it will escape through those little holes in the top, which is why those new fangled batteries with sealed tops explode when they get too much smoke in them.

With regard to Joseph Lucas and his wrongfully sullied reputation, why is he so maligned? Why are Lucas components more likely to leak smoke then, say, Bosch or Marelli? Because Lucas is British and British things always leak. British motorcycles leak oil, British sports cars leak oil, British hydrolastic units leak fluid. and British governments, leak military secrets. So, naturally, British electrical components leak smoke


4x4 Earth Contributer
Very funny! I think your'e right. I remember when I bought an old second hand Tandy 1000 personal computer a few years ago. After only a couple of days use, I smelt that nasty acrid smell that an appliance often gives off in its death throes.

Then the picture on the monitor shrank slowly into the middle of the screen. And just as it became a tiny dot in the centre, this sorry little plume of blue smoke curled up from the back of the unit.
I thought I was watching a bugs bunny cartoon. It was just as they portray it in the kid's shows on the tele!

Had a big laugh when I saw that plume of smoke slowly rise.

But now I know why siegreich! Thanks for that. It all makes good sense to me now.
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My god you all need to get a life, information explosion, I just want to know which battery I should buy to run as my auxiliary battery for the fridge and should my winch be hooked to the main battery or the auxiliary battery. LMAO:D


Batteries are the heart of any vehicle's electrical system. To understand why use of battery enhancement technology aids overall vehicle performance, it is important to understand the 3 functions of a battery
1. Supply power to the starter and ignition system so the engine can be started.
2. Supply extra power when the vehicle's load requirements exceed supply from the charging system.
3. Act as a voltage stabilizer in the electrical system, reducing temporary high voltages, which occur in the vehicle electrical system. These high voltages would damage solid-state components in the electrical system if it were not for the protection provided by the battery.

Battery plate sulfation occurs and increases every time your battery is used. It is part of the chemical reaction, which takes place in the battery. When a battery is sulfated, its voltage is depressed. The battery no longer meets the demands of the vehicle electrical system, and from an electrical perspective it "disappears". Electronic and electrical components then receive current directly from the alternator, and are subject to over-voltages. This results in premature failure of electronic components.

A lead acid battery is an electrochemical device, which stores chemical energy. This chemical energy is converted to electrical energy when the battery is connected to an external load such as a vehicle starter. The chemical energy is created by the chemical action between the materials which form the positive and negative plates of the battery, and the electrolyte:

Lead Dioxide (PbO2) Positive Plate
Sponge Lead (Pb) Negative Plate
sulfuric Acid (H2SO4) Electrolyte.

A battery relies upon clean plates and strong electrolyte to receive charging current and offer discharge current. When the battery is connected to a load, the sulfate (SO4) in the electrolyte combines with the active materials of the plates to form lead sulfate (PbSO4) and release electrical energy. Electrons flow from the negative terminal to the load and back to the positive terminal of the battery.

The Battery specific gravity (ie. the unit of measurement of the sulfuric acid content of the electrolyte) of a fully charged 12-volt battery is 1.300 at 26.7 deg C. This means that the sulfuric acid of a fully charged battery is 1.3 times heavier than pure water. As a battery becomes discharged, the strength of the specific gravity decreases because sulfur is leaving the electrolyte as it forms lead sulfate which adheres to the battery plates

State of Charge Specific Gravity Voltage (12V battery)
State of Charge Specific Gravity Voltage (12V battery)
100% 1.300 12.84
75% 1.250 12.50
50% 1.200 12.20
25% 1.155 11.90
Discharged 1.120 11.00

Thus by the time the battery is discharged, the acid becomes dilute as the sulfur has adhered to the plates of the battery as lead sulfate crystals. When a discharged battery is recharged, the chemical processes within the battery operate in reverse. The majority of the sulfate leaves the plates of the battery and returns to the electrolyte. However, a residue of sulfate remains on the plates of the battery. The quantity of this residue increases with each charge/discharge cycle of the battery. Over time, the battery plates become coated with an insulating layer of sulfate and the electrolyte is weakened because of the loss of Lead sulfur molecules from the solution. Both these factors serve to inhibit the electron transfers and thus the energy producing function of the battery.

Over time the sulfate deposits on the plates become hard and crystalline. When in this condition, plates will not accept a charge under normal conditions, and the accumulation of lead sulfate may cause short circuits during recharging or other mechanical damage to the battery. Often, hairline cracks appear in the plates causing open circuit conditions.

When a lead acid battery discharges or remains inactive, lead sulfate forms on the battery plates. Over a short period of time, sulfate gradually accumulates and crystallizes clogging the plates to the point where the battery will not accept or hold a charge. This process, known as sulfation happens to all lead acid batteries in all application. It is the leading cause of battery failure. Megapulse technology reverses sulfate accumulation in all lead batteries and it prevents sulfation from ever developing in new batteries. By pulsing a carefully controlled DC current into the battery, it re-energizes crystallized sulfates deposited on the plates and returns them to the electrolyte as active sulfur molecules. With the plates kept clean, batteries will provide more power, faster recharge and longer battery life.

Batteries commonly fail because of sulfation. sulfation occurs when a battery is discharged. The deeper the discharge, the more serious the sulfation. A battery relies on clean plates and strong electrolyte to both receive charging current and offer discharge current. A sulfated battery can do neither. sulfation also occurs when batteries are in an undercharged state. Battery theory states that cell voltage should read 2.45 volts per cell (i.e. 14.7 volts in the case of a 12 volt battery) from time to time to allow the negative plate to "form". If this does not occur, the negative plate remains mushy and subject to erosion from motion, vibration, etc. In automotive systems, alternators seldom exceed 14.2 volts. Battery theory states that 12-volt batteries must receive a minimum of 14.1 volts to maintain a charged state.

Hi, i had a new Century Hi Performance battery put in my Prado in April this year. My dual battery display always showed both batteries to be at 12.8 (obviously the aux. goes down when fridge on in car and car not running). I noticed in the last month or so that the main battery was showing 12.4, in the mornings before i started the car, it was always 12.8 before. I quizzed my local electrician and he said that 12.4 was normal after a battery had rested. He checked the acid and said it was fully charged at 12.4. Does this sound right? My display will show it charging at 14.0 for a while once driving but after some time will charge at 13.5. I gather this goes down when the batteries are full?
As you can gather i know very little about batteries!!!!!


New Member
You have given a very nice information about battery, I would also like to include something a battery is an electrical storage device, which can be found in a number of shapes, sizes, voltages and capacities. When two conducting materials are immersed in a solution, an electrical potential between them. When connected via a closed circuit, a current.