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What is a battery?
Typical applications
Choosing the correct size of battery
Battery storage, care & maintenance
Battery safety
Jargon made easy


What is a battery?

A battery is an electric storage device which can be found in any number of shapes, sizes, voltages and capacities.

Battery Cell with positive and negative plates  A battery is an electric storage device which can be found in any number of shapes, sizes, voltages and capacities. When two materials (often dissimilar metals) are immersed in a solution they conduct electricity, between the "plates" causing an electrical potential. The value of this potential (or voltage) is dependent on the materials used, giving rise to a whole family of battery types each having benefits and restrictions in use. Examples are:- lead acid, nickel cadmium (Nicad), lithium, silver alkaline.

This manual is concerned only with one battery technology - the most successful - lead acid - lead and lead oxide immersed in sulphuric acid. Each cell having a 2 volt potential. A battery is simply a number of cells connected together with a given voltage and capacity. The more cells the higher the voltage, the larger the plates the higher the capacity (in general).

Purely for convenience, batteries are made in 12 volt blocks with 6 cells but are also available in 6 volt, 4 volt and even 2 volt, single cell blocks.

You can however connect blocks in series to the required voltage, and blocks in parallel to the required capacity (see Choosing the correct size of battery).

battery voltage in a lead acid battery


The lead-acid battery

There are two concepts in lead-acid batteries

  1. Sealed or Valve Regulated Lead Acid VRLA

  2. Open - Vented

There are three basic applications

  1. Industrial

  2. Automotive (starter i.e. cars, commercial vehicles)

  3. Traction (electric motor drive i.e. milkfloat)


This guide is focused on Industrial Standby applications and NOT Automotive and Traction use.


Industrial batteries

Industrial batteries are available from two distinct groups with the following features. Note that VRLA have superseded open-vented in many applications.

Older technology
Environmentally friendly
Require separate battery room Use directly in office. environment
Regular routine maintenance Low maintenance - 'Maintenance free'
Separate safety requirements Self-contained. Safe
Store/use in vertical position Store/use in any orientation
Can require extensive cabling Can be used internal or adjacent to load
VRLA has in many instances replaced the open-vented type.

Note - the term sealed lead-acid SLA is an old acronym considered misleading and is now replaced by Valve Regulated Lead Acid VRLA.

Typical applications

The Yuasa range focuses on VRLA technology.

Typical Battery Applications for Yuasa Batteries

To optimise battery duty and life for your application, make sure you choose the right product from the Yuasa range.

Choosing the correct size of battery

As mentioned earlier, batteries come in all shapes and sizes, from types no larger than a shirt button, to a battery system filling an entire room.

To find the size of battery you require you generally need two pieces of information battery load and back-up times. (Note; other factors may also have an effect).


Battery Load

Whether you power lights, motors, electronic equipment or a toy vehicle your equipment will draw a load in AMPS. If this is unknown then the equipment will have a rating expressed in Watts which may simply be converted to Amps by dividing the value by the normal voltage of the system.

Example You have chosen NPC for high cycle life and wish to drive a power tool rated at 120 watts 12 volts.

Load current = 120 divided by 12 = 10 Amps


Back-up time

This is the time you require the battery to support the load described above and is often called Autonomy or discharge time. Example, To power a cordless electric tool for a total of 3.0 hours before recharging. With these two pieces of information use our selection graph to plot an intersection point from which you will determine a required size or capacity in Amp. hours (Ah).

Our figure No. 1 has been rationalised into rounded figures of capacity. If your intersection point falls between two lines choose the next highest value.

Fig No.1 NP Types

Correct charging of a VRLA battery is essential in optimising battery performance and life.

Always choose a suitable sized battery from the ranges appropriate to your application.

You may notice that the chosen capacity in Amp hours is often higher than the Value of Amps x Hours used, in our example using 10 AMPS x 3 HRS = 30 Ah and the chosen option being 38Ah. This is because the capacity 'cA' of each NP battery is stated at the 20 hour discharge rate. You will only get full capacity if discharged over this length of time.

Note:- This explanation is a simplified version, if in any doubt call our Technical department on 01793-645753.

Simplified Selection Matrix
A = Excellent B =Good C =Fair
Float Life upto 5 years B A - B A
Cyclic Life C C A B B
Float Life upto 10 years - B - - A
High Rate Discharge B B - A B
Float Charge Applications A A B A A
Energy Density C20/C10 B B B B B
Specific Energy C20/C10 B C B B B
Specific Energy C1/0.5 B B B A B
Portable Applications C B A B -


Correct charging of a VRLA battery is essential in optimising battery performance and life. Although a constant voltage charge should be applied, optimum charging also depends on temperature (Nominally 20°C), charge current (max 1/4 battery capacity) and ripple current (minimum). Two basic categories of charging exist.


This charging method is used in applications such as emergency back-up when the battery is required only upon mains failure e.g., Alarm Panels, Emergency Lighting, UPS. In each case the battery is continuously on charge and consequently the recommended voltages are slightly lower than cyclic charging so as not to damage the battery. (Float voltage for Yuasa NP range = 2.25-2.3 volts/cell). These figures may vary between different battery types.


Cyclic charging is used in applications where the battery is repeatedly discharged then charged, e.g. Portable equipment, Wheel Chairs, Golf trolleys etc.

A higher charging voltage is used but should NEVER be left on indefinitely since it will overcharge and destroy the battery. (Cyclic voltage for Yuasa NP range = 2.4 - 2.5 volts/cell)

For optimum performance always recharge a battery immediately after discharging.

Note - Consult the individual battery specification for the correct charging voltage or contact Yuasa Technical Department on 01793-645753

Battery storage, care & maintenance

The storage or shelf life of a VRLA battery is usually between 12 to 18 months at 20°C starting from a charged condition.

Warning - Never store in a discharged or partially discharged state.

Always store in a dry, clean, cool environment in a fully packaged condition.

If storage of 12 months or longer is required supplementary charging will be required.


Design Life

Each battery type will have a prescribed float design life. Please be aware of this life expectancy and replace the battery as end-of-life approaches. Keep a reference or label the battery to show its date of installation as this will indicate replacement at the right time.

Each battery suited to cyclic use will have a prescribed quantity of cycles to end of life and is dependant on depth of discharge. The depth of discharge is expressed as a percentage of the capacity required per duty cycle.

Near the end-of-life the standby capacity of the battery will reduce. When this reduction becomes persistently regular, this indication can also be used for the time of replacement.


Battery Care

Each Yuasa VRLA battery should be supplied in a charged condition having passed stringent quality checks.

To ensure optimum battery performance and life, it helps to take care of your battery by observing the following:



WARNING - Never leave a VRLA Battery in a discharged state.

If a battery has an open-circuit voltage lower than its rated value, then sulphation may well be the cause.

When a battery is left in a discharged state or for prolonged periods of storage lead sulphate crystals begin to form acting as a barrier to recharge and will prevent normal battery operation.

Depending on the degree of sulphation, a battery may be recovered from this condition by constant current charging at a higher voltage with the current limited to one tenth of the battery capacity for a maximum of 12 hours.

Note the applied voltage will exceed the normal recommendation and so the battery must be monitored (not left unattend) and removed from charge if excess heat is dissipated. The voltage required to "force" this maximum current into the battery will reduce as the battery recovers until normal charging can take place.

In extreme circumstances a battery may never fully recover from sulphation and must therefore be replaced.

If in doubt call Yuasa Technical Dept 01793-645753



As mentioned in Section 'Charging' optimum charging relies mainly on voltage, current and temperature factors which are interrelated and all of which can cause overcharge.

Excessive charge voltages will force a high overcharge current into the battery, which will dissipate as heat, and may cause gas emission through the safety valve. Within a short period of time this will corrode the positive plate material and accelerate the battery towards end-of-life.

Under these conditions the heat produced inside the battery can lead to thermal runaway due to the increased electrochemical reaction of the battery. The battery may swell before failing and will be irrecoverable from this state.



Warning -Heat Kills Batteries

Warning - Heat Kills Batteries

The recommended normal operating temperature is 20°° -25°C.

HIGH TEMPERATURE will reduce battery service life often quite dramatically (see figures 2 and 3), and in extreme cases can cause Thermal Runaway, resulting in high oxygen/hydrogen gas production and battery swelling. Batteries are irrecoverable from this condition and should be replaced.

Figure 2

Temperature (°C) 20° 25° 30° 35° 40° 45° 50°

% Expected Float Life








High temperatures in batteries give increased performance but only at a loss in life

Notice that high temperatures will give increased performance but only at a loss in life.

LOW TEMPERATURES will help to ensure a long service life but batteries used at low temperatures have reduced performance.

For detailed information contact Yuasa Technical Dept 01793 - 645753

Battery safety


Safety Batteries are electrically live at all times, take great care never to short-circuit the battery terminals.


High D.C. voltages, are more dangerous than the mains.


Batteries are often heavy, take care when lifting and transporting batteries. For weights above 24 kilos, lifting aids should be used.


Do not attempt to remove battery lid or tamper with the battery internal workings. VRLA Batteries are "low-maintenance" requiring no electrolyte top-up or measurement of Specific Gravity.

Battery Safety is important batteries are for powering machinery


disposal of batteries all all kinds of batteries and automotive batteriesFinally, when a battery has reached the end-of-life it must be returned to the point of sale or to a licensed battery dealer for recycling. Please observe the following points.


caution do not throw away batteries because they are dangerousCaution

Do not throw batteries in a bin at end-of-life. VRLA batteries contain substances harmful to the environment so return to your supplier or take to your Council tip for disposal.


Never bury in the ground or incinerate at end-of-life. Batteries contain harmful substances making this unsafe.

always return spent batteries to a stockist of batteriesAlways

Return the spent battery to your Stockists, the Local Council tip or any licensed battery dealer for recycling.


Jargon made easy


VRLA - Valve regulated lead acid battery.

SLA - Sealed Lead-acid.

CCV - Closed - circuit voltage.

OCV - Open - circuit voltage.

WPC - Watts per cell.

Pb - Chemical symbol for lead.

UPS - Uninterruptible power supply.

Ah - Amp hour. The unit of battery capacity.

DOM - Date of manufacture.

EOD - End of discharge.

VPC - Volts per cell.

NC - Number of cells.

Vf - Float Voltage.

VS - Starting Voltage.

IAV - Average current.

Sg - Specific gravity

cAn - Defined capacity of the battery to the 'n' time period.

20 hr Rate - The capacity a battery will deliver over 20hrs.



Battery - one or more cells

Float/Standby - Continuous charging for use in a emergency or back-up application

Cyclic - Continual discharge/recharge application often associated with traction applications.

Battery String or Bank - A number of batteries connected in series will constitute one string. Strings can then be connected in parallel to achieve the required capacity.

Monobloc - A phrase used to describe a multi - celled single block.

Wet/Flooded - Open-vented lead-acid cells which need topping up, i.e. not maintenance free.

Stationary -Applications using static placed batteries.

Top - charging - A service charge during or after storage, usually at a level slightly higher than normal float V.


Did You Know?

In addition to one of the widest range of Valve Regulated lead acid batteries available in the world - Yuasa also offer Lithium Primary Cells; Nickel - Metal Hydride rechargeable batteries and Nickel - Cadmium batteries. Full technical information on these battery types are available on request.


PowerFilm Lithium Cell
The Yuasa 'PowerFilm' is a Lithium 3 volt cell that is, only 0.2 mm thick and uses solid polymer electrolyte (SPE). Measuring only 29.3 mm x 22.3 mm its construction incorporates a Lithium Anode and a manganese dioxide cathode separated by a solid polymer electrolyte. These are encased between two micro-thin metal foils that also act as an external case and the positive/negative collector. A significant packaging development is the sealing of the outer edges of these collectors using a sealing compound that also provides the electrical insulation between the two polarities of the current collectors. This feature makes it the safest Lithium Primary Cell available. The Yuasa 'PowerFilm' also represents the highest power density SPE Lithium Primary cell in commercial production.

Nickel - Metal Hydride
Yuasa Nickel-Metal Hydride batteries are designed for applications covering portable electronic OEM products, computers, and telecommunications.

Yuasa 'Prismatic' Nickel - Cadmium batteries
These batteries offer what is believed to be one of the highest energy profiles available in Nickel Cadmium compared to similar sized batteries.


Yuasa has applied over 80 years of experience of lead acid battery technology in the production of VRLA type batteries with a choice of 60 different models from six different ranges.

Standard NP
Available in a wide range of sizes to suit general applications.

High performance batteries specially designed for applications requiring high rate discharge supplying up to 50% more power (watts) for short durations when compared to conventional NP models.

The extended service life version of the NP designed for normal standby and float service applications. NPL's now available to BS6290pt4.

Specifically designed to suit the arduous requirements of cyclic applications allowing increased cycle life (at least double that of conventional types).

The premium long life battery from Yuasa (that) fully complies with BS6290pt4 and 1EC896pt2.

Extra long life batteries. 15 year design life.

We have Quality Assurance Standard BS5750 ISO 9000 Part 2 for our UK battery manufacturing plant. Our customers can be assured that when they choose Yuasa they are choosing a state-of-the-art power source manufactured to the highest attainable quality standard.


For further information on our products your local distrubutor or stockist is fully qualified to help you.

You are of course welcome to make contact direct with any of our Sales & Marketing Companies in the UK, Germany, France and Italy.


Hawksworth Industrial Estate
Swindon Wiltshire SN2 1EG UK
Tel: (01793) 645700 Fax: (01793) 645701

Centre D'Affaires Evolic
14 Rue de Bruxelles
38070 Saint-Quentin Fallavier France
Tel: 00334 749 59098 Fax: 00334 749 59081


European Manufacturing Plant

Ebbw Vale Gwent Wales