Battery Definitions - battery university

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Battery Definitions

Batteries come in all shapes and sizes and there could be as many types as there are species of dog. Rather than giving batteries unique names as we do with pets, we

distinguish batteries by chemistry, voltage, size, specific energy (capacity), specific power, (delivery of power) and more. A battery can operate as a single cell to power a

cellular phone, or be connected in series to deliver several hundred volts to serve a UPS (uninterruptible power supply system) and the electric powertrain of a vehicle.

Some batteries have high capacity but cannot deliver much power, while a starter battery has a relatively low capacity but can crank the engine with 300A.

The largest battery systems are used for grid storage to store and delivery energy derived from renewable power sources such as wind turbines and solar systems. A

30-megawatt (MW) wind farm uses a storage battery of about 15MW. This is the equivalent of 20,000 starter batteries and costs about $10 million. One mega-watt feeds

50 houses or a super Walmart store. Lets now examine each of the battery characteristics further.

Chemistry

The most common chemistries are lead, nickel and lithium. Each system requires its own charging algorithm. Unless provisions are made to change the charge setting,different battery chemistries cannot be interchanged in the same charger. Also observe the chemistry when shipping and disposing of batteries; each type has a different

regulatory requirement.

Voltage

The imprinted voltage refers to the nominal battery voltage. Always observe the correct voltage when connecting to a load or a charger. Do not proceed if the voltage

differs. The open circuit voltage (OCV) on a fully charged battery can be slightly higher than the nominal; the closed circuit voltage (CCV) represents the battery voltage

under load or on charge and the readings will vary accordingly.

Capacity

Capacity represents the specific energy in ampere-hours (Ah). Manufacturers often overrate a battery by giving a higher Ah rating than it can provide. You can use a

battery with different Ah (but correct voltage), provided the rating is high enough. Chargers have some tolerance to batteries with different Ah ratings. A larger battery will

take longer to charge than a small one.

Cold cranking amps (CCA)

CCA specifies the ability to draw high load current at 18C (0F) on starter batteries. Different norms specify dissimilar load durations and end voltages. See

Abbreviations / Conversions.

Specific energy and energy density

Specific energy or gravimetric energy densitydefines the battery capacity in weight (Wh/kg); energy density or volumetric energy densityis given in size (Wh/l). A battery

can have a high specific energy but poor specific power (load capability), as is the case in an alkaline battery. Alternatively, a battery may have a low specific energy but

can deliver high specific power, as is possible with the supercapacitor. Specific energy is synonymous with battery capacity and runtime.

Specific power

Specific power or gravimetric power densityindicates the loading capability, or the amount of current the battery can provide. Batteries for power tools exhibit high specific

power but have reduced specific energy (capacity). Specific power is synonymous with low internal resistance and the delivery of power.

C-rates

C-rates specify charge and discharge currents. At 1C, the battery charges and discharges at a current that is par with the marked Ah rating; at 0.5C the current is half, and

at 0.1C it is one tenth. On charge, 1C charges a good battery in about one hour; 0.5C takes 2 hours and 0.1C 10 to 14 hours. Read more about What is the C-rate?

Load

A load draws energy from the battery. Internal battery resistance and depleting state-of-charge cause the voltage to drop. Physical work over time is energymeasured in

Watt-hours (Wh).

Watts and Volt-amps (VA)

Power drawn from a battery is expressed in watts (W) or volt-amps (VA). Watt is the real powerthat is being metered; VA is the apparent powerthat determines the wiring

sizing and the circuit breakers. On a purely resistive load, watt and VA readings are alike; a reactive load such as an inductive motor or florescent light causes a drop in the

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power factor (pf) from the ideal one (1) to 0.7 or lower. For example, a pf of 0.7 has a power efficiency of 70.

Comments

On April 24, 2011 at 12:48am

Richard Sergeant wrote:

Power is always V.I. cos.f. Can cos.f, the phase angle, be other than unity for power supplied by batteries?

On August 5, 2011 at 4:50am

Mr Varrie Adamson wrote:

I have a BT5500 Freelance Phone with 550mAh batteries - I have had problems finding same to replace. Can I use 900mAh instead?

On August 9, 2011 at 8:54pm

Dave Anderson wrote:

Electromotive Force is expressed in Volts. It is not a load.

On August 13, 2011 at 4:16pm

Alex wrote:

Mr Adamson,

as long as voltage and battery type are the same a higher mah rating is fine, as it means it will just last longer. A 900mah battery will last nearly twice as long as 500 mah.

So yes if its correct type get that one!

On October 15, 2011 at 5:10am

sharmilawrote:

require updates from battery


sharmilawrote:

whats the difference between capacity and specific capacity


jackie wrote:

Have added my comments a few moments ago. How should i search to find out what units i can use my existing but undefinable battery on? (identification info is the battery adapter, 0801S

model number D12-03A. I tried to translate your battery identication from your Univserity info., but to no avail - all slipped right over my head. Im asking for a few search steps and or

shortcuts so I may learn where I may plug this adapter into rather than simply tossing it out & tomorrow find out maybe that was the adaptor I required. thank you Ill wait to read youjr email .


Muruhan wrote:

Sharmila, Specific capacity is not discussed in this page with respect to battery.

On February 1, 2012 at 6:04pm

De wrote:

I read through all the comments and they are useful. Thanks to all

I also have 12V 4Ah battery for the alarm system. I did not read the label before buying new one on ebay and I already bought 12V 7Ah and can not return. According to Alex I can use the 7Ah

as long as it is the same Voltage.

Question is can my system charge this higher 7Ah battery?

On May 16, 2012 at 7:46am

Ron wrote:

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Theoretically, the only problem would be that the amount of time it would take to charge the higher Ah battery would be greater, since the charging circuite would be supplying the same current

as before. i.e. if the charging circuit supplies say 1A, it would take 4 hours to charge your old and 7 to charge your new battery.

However, it is my personal experience that when a charging circuit is designed for a lower capacity battery, a higher capacity battery does not charge as properly. But i am still investigating why

that is, and i think it is due to a voltage mismatch between the charging circuitry required for the two different batteries.

Anyway, i realised now from your comments timestamp that my answer is now redundant.

On May 23, 2012 at 4:11pm

larry wrote:

Minor error on this page under Load. The Volt is the unit of Electromotive Force (EMF). It is a measure of the motive force that drives current through a load. The unit of current is the amp.

Of course, basic OHMs law applies at DC ie., E=IR.

On November 4, 2012 at 12:14am

Peter R trevallion wrote:

As a complete novice of solar and wind generating low voltage power, I find that the pages on your internet site are an invaluable source of information for me.

Many, many thanks.

P.R.T.

On November 29, 2012 at 6:36pm

Bee Tee wrote:

I have need to replace Golf Buggie 2x12 volt 75ah deep cycle batteries for which I am being asked 460:

I have found web sites offering similar spec batteries for half that price. Do you think there are quality differences which justify buying the higher price ones?

I have zero knowledge of this subject and am learning from your interesting site -Many thanks -BT

On December 3, 2012 at 8:42pm

Pratik wrote:

I am planning to buy a mobile, but the cell gives less back up. Other features are perfect.

What will happen if i replace the battery by increasing just the Amphere of the cell, keeping voltage constant.

On December 29, 2012 at 3:25pm

Terri wrote:

I am trying to find the smallest battery needed for my waverunner to only charge my cell phone, GPS and wireless speaker. Can you tell me the best battery I would need? -Thanks TL

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Battery Definitions - battery university