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All You Need To Know About Lead-acid Batteries

Table of Contents

All You Need To Know About Lead-acid Batteries


1. Always rotate your stock. Practice FIFO (First In, First Out). Lead-acid Batteries slowly lose their charge, and good stock-rotation stops batteries going flat in storage and makes sure that the, customer buys a good battery. On the back of the battery. There is a label showing the expected period before the battery will require recharging. This makes it easy to identify the oldest and newest batteries in stock. Please use the recharge date to ensure that the oldest batteries leave your stock first. Recharge date is only an indication of recharge period as self discharge is subject to storage conditions.

2. Store Lead-acid batteries in a cool, dry, well-ventilated area.

3. Protect Lead-acid batteries from excessive heat. (Heat causes batteries to lose charge more quickly, and excessive heat can damage batteries).

4. Store Lead-acid batteries in an upright position. (To stop them falling over or leaking).

5. Do not stack batteries on top of other batteries. (To avoid scratching, and tearing labels. To avoid damaging terminals that stand proud of the lid).

6. Store shrink-wrapped batteries up to 3 high. (Any higher and there is a risk of them falling over and injuring people).

7. Do not remove any seals from dry-charged batteries until you are ready to commission the battery by filling it with acid. (The seal preserves the charge in the battery. If it is broken, air will enter and cause the battery to lose charge).

8. Store batteries on racks or on pallets, not on the floor. (Small stones or sharp points on a concrete floor can damage the base of the battery and cause leakage).

9. Make sure handles are left in the flat (down) position. Upright handles are more likely to be damaged.

Maintenance of Stock Handling and Recharging of Lead-acid Batteries

WET-Charged Batteries

  1. Lead-acid Batteries should be installed ideally within 15 months after manufacture. The voltage should be (worse case higher than 12.25 Volts) ideally higher than 12.4 Volts at the time of installation.
  2. Lead-acid Batteries require recharging when the voltage has dropped below 12.4 Volts due to extended warehouse storage. All safety precautions should be undertaken prior to recharging batteries. See charging instruction section in catalogue for further details. If a battery has been recharged, the recharge date on the back label should be updated by 6 months after second recharge date by physically notching the label. (Note: A maximum of two recharges are allowed prior to sale, and product should not be sold a maximum of 9 months after the expiry of first recommended recharge date).

2.1 A voltage check should be carried out as a matter of course, both to identify older stock and highlight batteries requiring recharge.

2.2 Use a digital voltmeter/multimeter with a minimum of 2 figure resolution (eg 12.76 Volts).

2.3 Scrap any batteries below 11.0 Volts (these batteries will have developed sulphation that cannot be completed reversed by charging and so will not give the expected performance and life to the customer.

2.4 Note Digital Conductance testers (such as Midtronics and/or Bosch BAT121) are: – NOT designed for the testing of new batteries. – Digital battery testers are not designed to check the fully developed cold cranking performance of a new battery. – They are designed purely for the testing and evaluation of faulty or used batteries. – Any CCA/state of health reading from the test on a new battery CANNOT be a reliable guide as to specification of the battery. – See comments on Digital Conductance testers.

DRY-Charged Lead-acid Batteries:Maintenance of Stock

Sales of dry-charged batteries within our range is very limited, usually for specialist markets and hence not listed in this catalogue.

  1. If you keep the batteries cool and dry, and do not remove the seal, dry-charged batteries do not need any other attention.
  2. The maximum storage time of dry-charged batteries before they are commissioned by filling with acid is 24 months.
  3. If the seal is damaged, the batteries should be wetted up immediately and the product then treated as WET-CHARGED batteries.

Removing Batteries and Installing Lead-acid Batteries on Vehicles

Removing Batteries

  1. It is good practice to tell the customer that, while you will do your best to keep the memory settings, it is possible these might be lost.
  2. Make sure the hand-brake is on, and that the car is in neutral or park. Switch off all electrical loads and remove the ignition key from the car. Note: On some cars, the doors will lock when the battery is disconnected so this is why the key should be removed from the car. Also switch off any non-factory -fitted alarms.
  3. Check that the cigar lighter is still working. If not, turn the ignition key to the auxiliary position. Install a Computer Memory Saver (CMS).
  4. Disconnect the earth-connector first. (This is normally the negative on modern vehicles). This can result in the loss of memory settings; please refer to the vehicle handbook.
  5. Disconnect the live-connector second. If a CMS is used, the connector will still remain live after it has been disconnected. To prevent the connector shorting against the car, place an insulator such as a rubber glove over the connector.
  6. Remove the hold-down clamps.

Preparation of a Lead-acid Battery for Fitting

  1. Check that the battery has the correct polarity for the vehicle.
  2. Check that the battery has the correct height for the vehicle. (If a battery is too high, it can short out on the bonnet or the bottom of a seat, or it can damage the bonnet).
  3. It is good practice to place the old and new battery side by side to compare polarities, hold-downs and performance-levels. Some batteries have hold-downs at both the sides and ends. Only the ones used for securing the battery on the vehicle need to be checked.
  4. Check that the battery is clean and dry.
  5. Check that the vent-plugs or manifolds are firmly in position.
  6. Check that the battery has a voltage above 12.40 Volts. If not, charge the battery or use another that has a voltage above 12.40 Volts.
  7. Ensure the 2 terminal caps are still fitted at this stage.

Preparation of the Vehicle

  1. Clear away any items on the battery-tray which might damage the battery. (Placing a heavy battery on a piece of sharp grit can puncture the bottom of the battery).
  2. Check that the connectors, the hold-down clamps and the tray are clean and corrosion-free. (If there is any corrosion, hot water will instantly remove this). If there is severe corrosion which might affect the stability of the battery or has affected other parts of the engine compartment, have the vehicle checked by an authorised distributor.
  3. Check that the alternator drive-belt tension is correct. Refer to the vehicle handbook or service manual.
  4. It is recommended that the electrical system, and particularly the charging system, of the vehicle be checked to make sure it is operating correctly. Refer to the vehicle handbook or service manual.

Installing the Lead-acid Battery

  1. Fit and tighten the hold-down clamps. These should be tight enough to secure the battery and not allow it to move. DO NOT OVERTIGHTEN.
  2. Connect the live-connector first to the correct battery-terminal (normally the positive) after removing the terminal cap. DO NOT OVERTIGHTEN.
  3. Connect the earth-connector to the other terminal after removing the terminal cap. DO NOT OVERTIGHTEN.
  4. Place the 2 terminal caps on the old battery that has been removed from the vehicle to avoid the possibility of short-circuits.
  5. Replace onto the new battery any components that have been taken from the old battery such as exhaust tubes, vent-elbows, terminal covers, removable hold-down strips (widgets) etc.
  6. The use of petroleum-jelly (Vaseline) is not necessary on modern polypropylene batteries, but there is no disadvantage in using it. Smear lightly on the terminals. It is still recommended for hard-rubber batteries. Do not use grease.
  7. Remove the CMS. 8. Start the engine. 9. For non-automotive applications, install the battery in line with the equipment-supplier’s recommendation.

Charging Off-Vehicle

  • Do NOT charge a battery if its temperature is below 3°C as the electrolyte may have frozen.
  • Charging the battery on the vehicle is not recommended.
  • Refer to Section F for information about removing the battery from the vehicle.
  • ‘Sealed and AGM’ vehicle batteries should be charged only on constant potential chargers or ‘smart’ chargers. Do not charge on constant current chargers or boost chargers. ‘Sealed’ vehicle batteries do not allow any access to the electrolyte, and so cannot be topped up. There are no removable vent-plugs or manifolds. The battery is able to vent gases through breathing holes, and so it is not strictly sealed.
  • A new, unused battery with a voltage below 11.00 Volts should be scrapped and not charged.


These maintain a fixed, constant, preset voltage throughout the charging period. The current cannot be set and will fall as the battery state-of-charge increases.

Charging Procedure with Constant Potential and Modified Constant Potential Chargers 

  1. These chargers are normally designed to charge one battery at a time.
  2. Stop charging when the battery is gassing freely and the battery-voltage shows no increase over a period of at least 2 hours.
  3. Note: The majority of constant potential chargers are incapable of charging a severely over-discharged (below 11.00 Volt) battery in a realistic period of time. A minimum of 24 hours is normal. It might be impossible to charge an overdischarged battery.


The majority of commercial chargers, particularly home-chargers, are of this type, and allow neither the voltage nor the current to be preset.

Charging Procedure with Modified Constant Potential Chargers

  1. Use the same procedure as for Constant Potential Chargers in the paragraph above.


The latest generation of chargers is able to check the battery condition, and to supply automatically a controlled charge that will charge the battery in the fastest time without damaging it and without overcharging it at the end of the charge. Some ‘smart’ chargers have a special setting for all-calcium batteries and will charge these from flat, which most other chargers are unable to do.

Charging Procedure with ‘Smart’ Chargers

  1. Follow the manufacturer’s instructions.
  2. These chargers should be able to charge overdischarged (below 11.00 Volt) batteries. Note that some have a special setting for all-calcium batteries.


These provide a very high initial current, and are used mainly to put some charge into a flat battery when it is needed urgently by the customer. The current falls as the battery state-of-charge increases, and the battery temperature is monitored to make sure it does not overheat.

Charging Procedure with Boost Chargers

  1. Boost charging is not recommended except in exceptional circumstances eg a stranded customer, as this will reduce battery life, especially if a battery is boost-charged more than once.
  2.  Never boost-charge any battery that is below 11.00 Volts as it will be too sulphated to accept a charge; scrap the battery or charge normally.
  3. Only use a boost-charger that limits the charging voltage to a maximum of 14.2 Volts and that has a temperature monitor.
  4.  Follow carefully the charger-manufacturer’s instructions. 

Checking Lead-acid Battery Performance


  1. The latest generation of testers is digital. Examples are Midtronics and Bosch testers. These will give an immediate decision on about 80 per cent of batteries in service, including flat ones. In the remaining 20 per cent of cases, the batteries need recharging before testing.
  2. These testers show whether the battery is in a good, charged condition, whether it is discharged or whether it needs replacing.
  3. Note: This is the preferred method of checking batteries as it does not take any charge out of the battery. It is also easier, quicker and safer.


As reported by most battery manufacturers, some confusion has been created within the battery industry regarding the apparent performance of batteries after tests conducted with digital conductance testers (e.g. Midtronics, Bosch BAT121 being the most common types currently on the market). It is important that the purpose of these tester is clearly understood.

Digital conductance battery testers are not designed to check the Cold Cranking Performance of a new battery.

They are purely designed for testing and evaluation of suspect or used batteries. Any CCA or state of health reading from the test CANNOT be a reliable guide as to the specification of the battery.

The BCI and European EN standard as a testing benchmark for manufacturing process.

Brava Batteries is one of the big manufacturers worldwide of lead-acid automotive batteries and its batteries are designed to confirm to the internationally recognised standards.

For example, the initial performance testing procedure according to the EN50342.1 A1 Nov 2011 requires a minimum of 12 working days of testing and significant resources in equipment to validate batteries. All Brava branded batteries sold into the market and regularly audit tested to ensure conformance to the relevant standard.

The EN 50342 standard has created further confusion in the market by listed two conformance level standard for high rate cold cranking performance which are not clear to the end user without full access to the ETN part number listing.

Maintenance in Service


Always refer to the information contained in the handbook or brochure supplied with the vehicle or equipment.

Definition of Maintenance-Free

  1. Our starter batteries for cars and commercial vehicles conform to the relevant sections of EN50342.1 A1 Nov 2011 for maintenance-free characteristics. This means that in normal vehicle applications in temperate climate operation, it is not necessary to add water.
  2. Our batteries are designed to be topped up with water if water should be lost owing to, for example, a charging system fault, prolonged operation in hot climates, excessive off-vehicle charging etc.
  3. Note: The term maintenance-free applies only when the battery is used in an approved automotive or commercial vehicle application.

Definition of Low Maintenance

  1. Low maintenance batteries in normal vehicle applications in temperate climate operation need water-addition only at yearly intervals.
  2. Our batteries are designed to be topped up with water if water should be lost owing to, for example, a charging system fault, prolonged operation in hot climates, excessive off-vehicle charging etc.
  3. Note: The term low maintenance applies only when the battery is used in an approved commercial vehicle application.

Lead-acid Battery Maintenance in Automotive Applications

  1. Carry out the checks below at the recommended vehicle service intervals.
  2. Check the electrolyte-level and top up with water if necessary.
  3. Check that the battery is clean and dry and that the vents are not obstructed.
  4. Check that the terminal-connectors and the hold-down clamps are securely connected and corrosion-free.
  5. If the battery is on a vehicle that is not to be used for an extended period (more than 1 month), disconnect it from the vehicle. Refer to Section F for information about removing the battery from the vehicle. Modern cars have electrical accessories that slowly discharge the battery even when the ignition key has been removed. Some accessories such as alarms, trackers, and phones can cause a battery to become discharged in a few weeks.
  6. Fully charge the battery before storage and give it a refreshing charge every 3 months.

Lead-acid Battery Maintenance in Non-Automotive Traction and Deep Discharge Applications

  1. Typical applications are lawnmowers, electric wheelchairs, caravans etc. The Leisure Battery range is recommended for these applications; standard vehicle batteries are not suitable.
  2. Ensure that the battery is always kept in as high a state-of-charge as possible. Always recharge immediately after use.
  3. Check the electrolyte-levels on a regular basis dependent upon use. Charging batteries regularly on a non-vehicle charging system may result in a higher rate of water-loss.
  4. Check that the battery is clean and dry and that the vents are not obstructed.
  5. If the battery is not to be used for an extended period (more than 1 month), fully charge it before storage, and give it a refreshing charge every 3 months.

Lead-acid Battery Maintenance in Non-Automotive Float Applications

  1. Typical applications are motor-generators, stand-by applications etc. The Leisure Battery range is recommended for these applications; standard vehicle batteries are not suitable.
  2. Batteries used in these applications should be changed every 2 years or more frequently. (Continuous charging, even from a well-controlled charging system, will result in internal degradation of the battery. This could result in the battery not giving its predicted output when required even though the battery appears to be fully-charged).
  3. Ensure that the battery is always kept in as high a state-of-charge as possible without causing excessive overcharge. Always recharge immediately after use.
  4. Check the electrolyte-level on a regular basis dependent upon use, but not less frequently than monthly. Charging batteries continuously on a non-vehicle charging system may result in a higher rate of water-loss.
  5. Check that the battery is clean and dry and that the vents are not obstructed.
  6. If the battery is not to be used for an extended period (more than 1 month), fully charge it before storage, and give it a refreshing charge every 3 months. See Section G.
  7. Best practice is to define a regular maintenance-routine, and to record the results. This should include such variables as the amount of water added to each cell, specific gravities in each cell, battery voltage etc.

Use of Lead-acid Battery Additives

  1. We do not recommend the use of battery additives.
  2. The use of these invalidates the guarantee.


What’s AGM & EFB Lead-acid Battery

  • Improved active mass efficiency, through better absorption of the acid
  • Increased lifespan due to minimal active material shedding due to battery design
  • Higher cold start values
  • Totally maintenance free – zero water consumption
  • Spill proof/leak proof
  • Designed to meet latest OEM vehicle demands
  • Compatible with sensitive electronic equipment
  • AGM technology now factory fitted to numerous luxury cars and “Stop-Start” vehicle where increased AGM battery features are required

Brava’s world leading motorcycle and industrial AGM (absorbent glass mat) technology comes to the automotive market. The Brava automotive AGM battery has been engineered to meet the growing extreme power demands of recently introduced vehicles now starting to enter the European aftermarket. Brava’s automotive AGM experience comes from vehicles such as the Mazda MX5 and the famous Toyota Prius and has now been launched for European vehicle battery designs.

The new Brava AGM European 096 and 019 sized batteries provide reliable starting whilst coping with the extreme power needs of the modern vehicle. Laboratory evaluation is boasting 4-5 times the cyclic durability of standard conventional flooded product and typically 16% higher starting power, even at lower temperatures. Increased reaction surface area ensures increased energy densities for faster engine rotation during starting and therefore maximising fuel efficiency.

The AGM batteries utilises the same absorbent glass mat technology as used in Brava Motorcycle and Industrial batteries which have been on the market for over 10+ years. This absorbent glass mat absorbs the battery’s acid, enabling a more efficient use of the cell’s volume without the need for electrolyte reservoirs, as needed with conventional flooded batteries. The absorbent glass mat gives a number of key benefits to the design of the lead acid battery:

  • Within normal operating conditions, the use of the individual cell valve design and glass mat plate separation ensures gas recombination occurs and ensures that no water is lost therefore negating the need for electrolyte reservoirs and freeing the user from maintenance.
  • One way venting system providing partial pressure in each cell ensuring 100% leak proof and safe handling.
  • The acid absorption of the glass mat means that the battery packs can be operated under higher pressures than conventional flooded batteries this has benefits including significantly prolonging battery cycle durability by minimising paste shedding.


What are the differences between flooded and AGM lead-acid batteries?

See above, AGM batteries are built using a glass mat separator which enable all the electrolyte required by the battery to be stored within the glass mat, also allowing any gasses given off during charging to be recombined into water meaning that the batteries are totally maintenance-free. The design benefits of the glass mat over conventional flooded batteries enable the battery pack to operate under higher pressure without the fear of insufficient electrolyte between the plates, leading to the step change in durability offered by AGM batteries over flooded. The quality of the glass mat is a critical item in ensuring the optimum life of the battery versus its application. This experience has been gained by Brava from over 10+ years experience in the field using this technology. The automotive application battery designs are balanced with greater high rate starting performance and cycle life for the increased service/technological requirements of modern vehicle designs.

What are the differences between GEL and AGM (starved) batteries?

Both are recombinant batteries (i.e. under normal operating conditions they recombine the gases given off during charging to form water) and both are classified as sealed valve regulated. The major difference is that in the AGM, the electrolyte is fully soaked into a special absorbed glass mat separator which immobilises the acid, whereas in the GEL batteries the acid is mixed with Silica to form a GEL also immobilising the acid. The benefits of AGM over GEL are that with the use of absorbed glass mat, the battery pack can be operated under a greater operating pressure so improving cyclic durability. With GEL, similar pack pressure can not be used so durability is usually provided by increased paste density which is good for life but not as good for high rate startability performance as required for automotive applications.

Why is charging voltage so critical to both GEL and AGM Lead-acid batteries?

Charge voltage is critical with these types of batteries as both are recombinant batteries. This means that the oxygen that is normally produced on the positive plate in all lead acid batteries recombines with hydrogen given off by the negative plate. The recombination of the hydrogen and oxygen produces water, which recycles back to the battery acid, therefore the battery is maintenance free and does not need topping up. The sealing vent used in the design ensures that a positive internal pressure is maintained to ensure the recombination of the gases occur and not allow the cell to dry out and fail.

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