How much energy can be stored in a battery?

Question

Can any one tell how much energy can be stored in the a single battery (12v) ?

If I want to store 10 kWh of energy then how to calculate the number of batteries required.

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Editing notes:

power -> energy
kW -> kWh

Answer 1

No, since batteries store energy, not power. Your question makes no sense since the units are wrong. It is like asking what percent interest your wallet holds.

Batteries store energy. Power is energy per time. This also means that energy can be expressed as power times time, like the kiloWatt-hours used to express the electric energy your house consumes during a billing period. Another common measure of energy is the Joule. A Watt (a unit of power) is one Joule per second. A kiloWatt-hour is therefore 3.6 MJ.

Batteries are usually rated in units of current times time. This does not directly tell you how much energy the battery can store, but can be a more useful value in deciding how long a circuit will run from a battery. For example, a car battery might be rated for 50 Ah. That means in theory it could source 50 A continously for 1 hour and then go dead. In practise it's never that simple, and there are various factors that effect battery capacity (the current*time rating), like temperature rate of discharge, previous history, etc.

Answer 2

10 kW from 12V -> 833Amps

10kWh from 12V batteries -> 833Ah capacity

Or seventeen 50Ah car batteries in parallel

Answer 3

Olin's answer is pretty good, but it's worth noting that batteries are rated in amp hours because many factors which affect the amount of voltage a battery can deliver in any particular situation have much less effect on the total amount of charge it will be able to deliver. A battery which would be 90% depleted after delivering 3600 Coulombs (1AH) at 12.0 volts under one set of circumstances would probably be 90% depleted after delivering 3600 Coulombs (1AH) at 10.2 volts, even though in the latter scenario it would have delivered 15% less usable energy.

It's also worth noting that trying to get charge from a battery quickly (i.e. trying to draw large amounts of current) will generally cause the output voltage to sag, reducing the amount of energy delivered per unit of charge consumed, and consequently reducing the total amount of energy one will be able to extract before the battery is depleted. Some batteries exhibit this behavior to a much larger extent than others. A simplified way of thinking about this is to think of a battery as being like a parking lot, with some combination of parking places and travel lanes. A parking lot in which every parking space had its own dedicated lane to the outside could be loaded and unloaded very quickly, but wouldn't be able to accommodate very many cars. A parking lot which crammed cars within a few inches of each other and had no dedicated travel lanes except right at the exit might hold ten times as many cars, but getting cars in and out would be very slow. Most parking lots are, of course, somewhere between those two extremes, but there is still considerable variation.

Answer 4

As people have noted, what is stored is, effectively, energy

Energy is a measure of how much work has been done or can be done.
Power is the rate and which work is done or the amount of work needs to be done or can be done.

A car may operate at 40 HP while driving under certain conditions.
That's power - as the name horsepower implies.
Power is the instantaneous measure of work being done.

If the same car operated for one hour at 40 HP then the energy used is 40 horsepower.hours. We do not usually hear HP.hours mentioned BUT we do hear of kiloatt hours or kWh when measuring electrical energy.

Batteries are often rated in Ampere.hours or Amp.hours or Ah.
A.h are actually NOT a measure of energy but they imply energy if we know the voltage as well.

The proper units of power (= instantaneous work rate) for a battery is Watts. The proper units of energy (= work done or doable) for a battery is Watt. seconds or Joules.

If we work for one second at a power of one Watt we do 1 Watt second of work or 1 Joule of work and use 1 Joule of energy.

For interest, we do about one Joule of work by lifting 0.1 kg a height of one metre against sea level gravity.

Now - all the above is true [E&OE] but liable to confuse. There is a vast amount about this on the internet. For now

Power = rate of doing work Watts or kiloWatts (1000 Watts = 1 kW.)
Energy or work done is measured in Joules.

1000 Joules = 1 kiloJoule = 1 kJ.

In one hour at one Watt we use 1 W x 3600 s = 3600 Joule = 3.6 kJ

Battery energy = Volts_average x Amp hours capacity = Watt hour capacity.

Battery energy density:

Energy density can be measured in two ways.

Volumetric energy density tells use how many Watt hours can b fitted into 1 litre
Mass energy density tells use how many Watt hours can be fitted into 1 kilogram.

How much battery capacity / mass / volume is needed to provide a certain number of Joule can be determined from data for the battery chemistry used.

Table below is somewhat out of date but gives some idea.

                    Wh/kg   Wh/l  

Carbon Zinc 9 60-120
Alkaline 162 398
Lithium 140-340 410-710
Lithium Ion 105-130 270-325
Lithium Polymer 120 250
NiCd 40-60
NimH 60-80
SLA 30
Silver oxide 130 500

Incomplete
More later maybe ...