Frequently Asked Questions

General Automotive Questions

Having a battery you can trust is more important than some may realize. Not only does it provide the power to start your vehicle, but it also plays other important roles in its operation of your vehicle.

The main function for most vehicle batteries is to supply power to the starter and ignition system so the engine can be cranked or started.

The battery also supplies the extra power necessary when the vehicle’s electrical load requirements exceed the supply from the charging system. This means that your battery must also help power all the electronics and accessories that come installed or that are plugged into your car or boat. East Penn’s AGM or Absorbed Glass Mat batteries have no free-flowing acid. Special micro-fiber glass mats absorb the acid so the battery will not spill or leak. This glass mat material helps reinforce the battery’s internal components improving its ability to withstand the demands of multiple accessory loads (your vehicle’s many electronics). The battery also acts as a voltage stabilizer in the electrical system. The battery smoothes out or reduces high voltage spikes, which can occur in a vehicle’s electrical system when loads are abruptly shut off. These excessively high voltages could damage other components in the electrical system if it were not for the protection provided by the battery.

Even in cool climates, a battery under the hood of your vehicle can reach damaging high temperatures. Tighter engine spaces and increased service demands have made under-hood-temperatures rise higher than ever before.

When it’s cold, engines are harder to start, and your battery is put to the test. Its ability to start your car can depend on how well it withstood times of higher under-the-hood temperatures.

That’s why Ultimate batteries utilize special features within the battery to withstand higher temperature conditions. Precision-filled pure electrolyte, reinforced internal components, and a special reactive formula are just some of the features used to deliver superior life and maintenance-free performance in any climate.

EMS’s lead-acid batteries are one of the most recyclable products on the planet. Lead-acid batteries have a higher recycling rate than glass, aluminum, and newspaper. In fact, virtually 100% of every battery component can be recycled to make a brand new battery.

When two unlike materials such as the positive and negative plates (the electrodes) are immersed in an electrolyte (such as a solution of sulfuric acid and water) voltage is developed. The voltage developed depends on the types of materials used for electrodes and on the electrolyte used. The voltage is approximately 2.1 volts for a lead-acid battery cell. A typical lead-acid battery consists of six cells and is called a 12-volt battery. Electrical current is produced by the chemical reaction between the electrodes and the electrolyte when there is a complete circuit between the positive and negative terminals. If a battery is rechargeable, such as a lead-acid battery, forcing current through the battery in the opposite direction with a charger will restore the electrodes and electrolyte to their original states.

The battery is part of a system. When installing your new battery, it is wise to check related components. Follow all safety instructions when handling batteries! Always disconnect grounded cable first and connect it last to prevent dangerous sparks! Do not attempt the following vehicle maintenance without training or proper instructions:

  • Check cables
  • Clean corrosion off battery hold-downs, cables, and trays
  • Verify voltage regulator and alternator output meet proper specifications
  • Repair shorts (any load that is on when it should be off) in electrical system
  • If a load is left on and battery becomes discharged, recharge promptly
  • Tighten cables properly and always secure the battery properly

Do not keep your battery at a low state-of-charge for long periods of time. Batteries will self-discharge if not used. Conventional automotive batteries perform best when they are at a full state-of-charge.

NOTE: Remember to always wear safety glasses and a face shield when working on or near batteries. Always protect your eyes!

No. Optimized power is not always reflected by CCA ratings. AGM batteries deliver power quickly to start the engine. A CCA rating measures cranking over a 30 second period. Cars today start in milliseconds due to improved electrical systems.

Fuel injection, computerized starting controls, and other enhancements allow vehicles to start quickly without the need for extended cranking. Premium batteries should deliver the right balance of life, power, and durability – not just starting power.

Unlike fuel consumption, a longer length of driving time can be both beneficial and detrimental to the longevity of a battery. Beneficial in the sense that frequent starting without enough time for the alternator to recharge the battery can be hard on it over time. Conventional automotive batteries perform best when they are at a full state of charge.

Adversely, the longer the vehicle is in use, the more vibration and shaking it undergoes. This can also cause additional wear on the battery over time as well. The hardest scenario on a battery; however, is not using it at all. Batteries that sit for long periods of time can lose power or self-discharge. If discharged for too long, this can cause permanent damage to the battery to the point where it cannot be recharged.

Accidental power drains (like leaving your headlights or dome lights on) that discharge the battery to the point that it doesn’t have enough power to start the vehicle. Draining the battery to a very low state-of-charge can do permanent capacity damage.

Another common cause of battery failure is from putting the wrong battery in the wrong application. For instance, if the vehicle requires a certain amount of starting power, installing a battery that isn’t designed to provide that much starting power will quickly wear out to the point of a no-start situation. Also, if the battery’s dimensions don’t align with the vehicle’s recommendations, it might not have a good fit and suffer damage from vibration or clearance issues. Always pay close attention to the Battery Application Guide and specifically follow its instructions.

Higher temperatures also have a detrimental effect on battery life. However, in the cold, oil and transmission fluids are more viscous so getting the car started requires more energy. In general, extreme temperatures, hot or cold, have an adverse effect on battery life. However, it’s the heat that does most of the damage, but more batteries actually fail when they’re put to the test in the cold.

The consumer driving experience continues to expect increased electrical functions and features, which forces vehicle electrical systems, and the batteries that help power them, to become more durable and efficient. The automotive industry is on an upward trend toward the use of Enhanced Life Flooded and AGM (Absorbed Glass Mat) products as a vehicle’s Original Equipment battery. These enhanced battery technologies add additional durability to the battery’s design to enable it last longer under less than ideal circumstances and demanding accessory loads. This helps accommodate complex vehicle electronics and the demand they put on the battery. An AGM design is also spillproof and valve-regulated. This makes it safer to put in more non-traditional locations like under the seat or other areas that would allow for more space under the hood for other engine components.

Mostly towards the end of the 1990’s, some of the biggest consequences to disconnecting the battery resulted in losing radio settings, seat positions, and side-view mirror adjustments. As we progress into the 21st century, the stakes of not taking the proper precautions before and after disconnecting the battery have increasingly become much higher as well as the need for more sophisticated methods and a broader knowledge base for adhering to these precautions.

For example, for most modern vehicles, the engine’s computer records things like engine misfires and oxygen-sensor performance, and confirms that, over time, the emission-control system is doing its job. Once battery power is disconnected, those settings are cleared and the vehicle needs to relearn this data. The impact of losing data collected by the vehicle can result from something as inconvenient as to failing an emission’s test (depending on the state of inspection) to something much more serious like damaging the battery due to incorrect voltage output settings. Several BMW, Audi, and Lexus vehicle models require the computer system to be reset after battery replacement. Mercedes-Benz models have specific instructions in the owner’s manual for electrical set up requirements, and a few Infiniti models even require the shift release to be reset after battery replacement.

While more extensive procedures can be found in higher end vehicles, other models are in no way immune to extra steps involved when disconnecting the battery. Hundreds of vehicle models require additional steps or precautions when replacing a battery which include:

  • Battery disconnection precautions
  • Power window, locks, and sunroof programming
  • Convenience accessory programming
  • Supplemental restraint and ABS system precautions
  • Resetting engine and body control systems

Any who replaced a battery should closely regard the need for system resets, safety precautions, or specific instructions when replacing batteries in modern vehicles. Be informed of what the individual owner’s manuals require for battery replacement as well as the numerous guides and resources that solely focus on battery replacement and reset procedures.

EN Batteries

Automotive manufacturers provide a designated amount of space to accommodate the battery’s size. They also require batteries meet certain specifications and performance requirements. Standards are developed to meet these needs through structured sizes, maximum overall dimensions, terminal arrangements, and other special features that may affect the battery’s fit. As cars become more sophisticated, the tolerance of these battery requirements become even more stringent to best handle the complicated needs of today’s vehicle.

EN is short for European Norm. The European Norm is an agreement between the countries in Europe to consolidate the specification of standards to enhance the efficiency of commerce. In Europe, EN Standards are gradually being adopted as a more uniform alternative to many different national standards. This EN Standard has been applied to automotive batteries.

It all comes down to one key objective, consolidation. Just as Europe has tried to improve international commerce by consolidating national standards, car manufacturers are applying this as a global strategy. In addition, European car manufacturers are located all over the world and have been most influential in the direction of the global industry. By choosing to adhere to a consolidated line of EN battery types, these manufactures can gain new efficiencies in reducing the variability across multiple vehicle platforms while meeting the increasing complexity of today’s vehicles. As a premier auto parts supplier, meeting this standardization helps increase your level of confidence in the compatibility and fit of an aftermarket battery as an OE replacement.

DIN stands for the Deutsches Institut für Normung. Recognized by the German Federal Government as Germany’s national standards body, DIN has been a member of the International Organization for Standardization (ISO) since 1951. While these standards were developed for Germany, many of their automotive standards have been used to develop EN standards but they are not always the same. It is important to remember that EN standards are for all of Europe and not just for one country.

In Asia, manufacturers conform to the Japanese JIS standard, while the Battery Council International (BCI) maintains the standards and specifications for North American battery manufacturers. In many cases, BCI a has assigned an equivalent number for either the EN or JIS size.


Marine Master
Marine Master batteries are renown for their proven dependability and solid performance. This flooded battery line offers a complete array of starting, dual purpose, and deep cycle solutions for virtually any marine need. Even under challenging marine conditions like wave pounding vibration, stubborn engine starting, heavy house power, auxiliary, and trolling, Marine Master batteries rise to the top in user-friendly, marine-tough service, and extended reliability.

Intimidator AGM marine batteries go above and beyond conventional flooded designs providing an enhanced durability that powers more accessories longer. This premium spillproof, maintenance-free battery has pioneered a new era in user-convenience and safety while delivering the optimum combination of starting, cycling, and deep cycle power.

Dominator Gel marine batteries take deep cycle service to even deeper levels. An innovative gelled electrolyte technology protects the battery from ultra-deep discharges providing the trolling and heavy house power to handle even the most serious boating and fishing needs.

Marine Master

  • DEEP CYCLE/STARTING (Dual Purpose)





Ideally, you could have one battery for starting and an auxiliary deep cycle battery for the trolling motor and accessories. If however, you can only have one battery on board, the one you choose depends on the power draw required.

For light to moderate-duty low amp draw service, choose the dual purpose battery, specially designed to handle both starting and cycling. For heavy-duty cycling, choose the deep cycle battery. This will give you enough cranking amperage to start your engine, and the most reserve power to keep your trolling motor and accessories running longer. (Always be sure that the replacement battery CA and CCA meet minimum engine starting requirements.)

Marine Master
Designed for Dependability

  • EXCLUSIVE MOLDED-IN DUAL TERMINALS provide an easy connection with post or corrosion resistant stainless steel stud.
  • OPTIMIZED FULL-FRAME PLATES better withstand severe service demands and provide maximum current transfer.
    • EXTENDED LIFE SYSTEMS include special separators to prevent life-robbing electrical shorts and protect power producing components.
  • FORTIFIED CURRENT CARRYING COMPONENTS resist vibration and maximize performance throughout the battery’s life.

AGM Enhanced Electrolyte Suspension System

  • SHOCK-ABSORBING SEPARATORS resist vibration and damage.
  • ENHANCED DURABILITY DESIGNS withstand wear of extended cycling service.
  • SUPERIOR ELECTROLYTE RETENTION prevents dry out and acid leaks.
  • LOWER CURRENT RESISTANT SEPARATORS improve current flow for faster starts.

Extreme Performance Gel

  • THICK, SHOCK-ABSORBING GEL AND HIGH DENSITY PLATES provide superior resistance to vibration and damage.
  • GELLED ELECTROLYTE CONSISTENCY prevents ultra-deep discharge damage from a uniform acid gravity.
  • SOLID GEL STATE won’t leak or spill like liquid electrolyte.
  • REINFORCED FIBERGLASS MAT AND EXCLUSIVE TANKFORMED PLATES prevent shorts and enhance electrical performance.

AGM (Absorbed Glass Mat) Batteries In Heavy-Duty Truck Applications

Unlike a “flooded” lead-acid battery, an AGM battery does not have free-flowing electrolyte. Separators made of mostly fine glass fibers hold the electrolyte like a partially saturated sponge.

AGM batteries are Valve Regulated Lead-Acid (VRLA) batteries that recombine the hydrogen and oxygen created during charge and discharge, back into water. This recombination keeps the battery water levels within proper limits. For this process to work, VRLA batteries must be charged at specific voltages.

Each cell contains its own valve. If the battery is overcharged, gas pressure builds within the cell rapidly. If the pressure exceeds one and a half PSI, the valve(s) will open and let the gas escape, thus the term “Valve Regulated”. If this continues, the battery will dry out and fail much like an overcharged flooded battery.

AGM batteries offer superior starting power, high reserve capacity, and long lasting life. The advanced AGM technology and dual-purpose design makes East Penn’s AGM battery excellent for quick starts and for powering accessories and creature comfort items when your engine isn’t running. An East Penn AGM battery is also excellent for battery powered HVAC systems. The group 31 AGM battery has the same case/cover configuration as a traditional group 31 battery, which allows it to be used as an original equipment battery or as a drop in replacement.

AGM batteries can be used in several applications including truck starting, dual-purpose, and deep cycle applications. Similar to flooded, AGM batteries have different designs ideal for specific applications.

  • AGM Starting batteries are designed for larger engines that need high cranking power like dump trucks and loggers.
  • AGM Dual Purpose batteries are designed for starting and dual purpose applications such as day cab, sleeper cab, and pick up and delivery.
  • AGM Deep Cycle batteries are a dual-purpose/deep cycle version designed for applications where the battery is the power source such as a battery-powered HVAC system.

No, you cannot mix AGM and flooded batteries within the same battery pack. AGM batteries should be paired together with AGM batteries of similar age and ratings within the same battery pack.

AGM (Absorbed Glass Mat) Technology

AGM stands for Absorbed Glass Mat.

A highly absorbent, micro-porous mat made of special glass fibers. The specially designed mats are an essential component in the battery’s electrolyte suspension system. All of the electrolyte is absorbed into this material enabling a spillproof design.

AGM batteries will replace a flooded battery in any typical alternator voltage regulated system. These systems generally maintain a voltage at 13.8 to 14.4 volts (cars, trucks, commercial trucks, boats, etc.). In fact, the efficient recharging of the AGM battery design can cause less wear on the vehicle’s alternator system over time.

AGM and conventional flooded lead-acid batteries are one of the most recyclable products on the planet. Lead-acid batteries have a higher recycling rate than glass, aluminum, and newspaper. In fact, virtually 100% of every battery component can be recycled to make a brand new battery. East Penn operates one of the most modern and environmentally-safe facilities in the world. This enables our customers to assure their customers that they are recycling their batteries with someone they can trust.

Yes. This advanced AGM technological design offers superior performance over conventional flooded batteries. All automotive batteries are expected to meet a certain level of performance standards for engine starting and to provide reserve power for the vehicle’s electronics. AGM batteries, however, are expected to excel in certain key aspects of battery use such as:


As the electrical, high heat, severe service, and durability demands continue to intensify for today’s vehicles, conventional flooded batteries may not deliver the dependable performance and service life needed under these conditions. This is not only the trend for cars and trucks, but now commercial trucks, marine vessels, and power sports vehicles are requiring a more evolved type of battery power.


Why do customers need better cycling performance from their batteries?
Today’s vehicles, and those to come, are being built with more factory-installed electronics and more places to plug in portable devices. For example, cars and other passenger vehicles have to provide power for items like LCD viewers, GPS systems, stereos and speakers, powered windows or doors, cell and smart phone charging, and anything else that plugs in or turns on. Boats need power for accessories like live-wells, GPS systems, stereos, hazard lighting, fish finders, and any other item that plugs in or turns on. Cars that utilize stop/start functions, like Micro Hybrid Electric Vehicles, demand extra durability and a better charge acceptance from their battery. As more types of electric vehicles evolve, so will the need for a higher cycling tolerance from the battery.

How do AGM batteries help to deliver better cycling performance?

AGM battery technology withstands these additional accessory power and cycling demands while still having the power to start the vehicle. An AGM battery’s enhanced durability and charge acceptance makes it an essential component for many stop/start and other electrical system technology. Its ability to have over twice the cycle life of a conventional flooded design gives it a clear advantage for its implementation into progressing electric vehicle technology.


Why do customers need better severe service durability from their battery?
Severe service and higher temperature conditions continue to escalate because there is less open space under-the-hood with more demand on the battery. Also, more vehicles undergo stop-and-start driving conditions, further increasing the need for enhanced durability.

How do AGM batteries help deliver better severe service durability?

AGM battery technology can be utilized to help offset these increasing power and durability demands. The AGM battery’s ability to withstand severe service and accessory power demands under elevated temperatures and stop-and-go conditions will better safeguard performance and extend battery life.


Why do customers need a better deep discharge resiliency from their battery?

Vehicles that aren’t used every day have a higher risk of not starting because of parasitic accessory power loads. Parasitic loads, or even leaving something on when the ignition is off, can completely drain the battery’s power.

How do AGM batteries help deliver better deep discharge resiliency?

AGM battery technology delivers a higher deep discharge abuse tolerance. This helps protect the battery longer from situations like infrequent use, parasitic power drains, or other deep power discharge (like leaving your vehicle’s lights on when the ignition is off).


Why do customers need a battery that resists vibration damage?
Vibration resistance is extremely important to protecting the battery’s life in almost any application that moves. Vibration or jolting movements can lead to electrical shorts or the loss of electrical storage capacity that can significantly decrease the battery’s performance.

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Cycle Life In AGM Batteries

A CYCLE is a single occurrence when energy is taken out of the battery and then put back in. CYCLE LIFE is the ability of the battery to do that over and over again and continue to deliver reliable performance.


Claims that a battery has extended LIFE could simply mean it survives longer than average in a typical automotive application in an average climate. In the real world, actual battery life is highly variable and unpredictable. The stresses on a battery differ by climate, vehicle differences, and user habits. A battery may last a long time under ideal conditions, but fail with only minimal abuse.

A battery with extended CYCLE LIFE survives longer than average under more grueling demands that portray a more realistic picture of real world use. This includes warmer climates, higher under-hood temperatures, longer than typical hours of usage, higher annual miles of operation, and frequent electrical loads while the engine is off.

Today’s vehicles, and those to come, are being built with more factory-installed electronics and more places to plug in portable devices. For example, cars and other passenger vehicles have to provide power for items like LCD viewers, GPS systems, stereos and speakers, powered windows or doors, cell and smart phone charging, and anything else that plugs in or turns on. Boats need power for accessories like live-wells, GPS systems, stereos, hazard lighting, fish finders, and any other item that plugs in or turns on.

Newer cars are also utilizing additional electronic functions in areas that were traditionally powered by the engine. This is not only the case for Hybrid Electric Vehicles, but is also being incorporated throughout a variety of standard automotive designs. These additional electronic services demand extra performance from the battery. As more types of vehicles evolve further into electrification, so will the need for the higher cycling tolerance and overall durability in a battery that can be found in the AGM design.

EMS’s AGM batteries have special glass mats that are strategically wrapped around the battery’s power producing components. The main reason for this mat is to absorb all the battery’s acid so the battery won’t leak or spill if turned over or if cracked. However, these mats also provide an added layer of protection for these components. This added protection enhances the battery’s durability against continual power drains like electronics. In fact, EMS’s AGM batteries have 2x the cycle life over traditional maintenance-free flooded batteries to power more accessories for much longer. This enhanced durability also protects the battery from vibration, high temperatures, the rigors of stop-and-go driving and frequent vehicle use.

VRLA AGM & GEL Batteries

Valve-Regulated Lead-Acid or VRLA, including Gel and AGM (Absorbed Glass Mat) battery designs, can be substituted in virtually any flooded lead-acid battery application (in conjunction with well-regulated charging). Their unique features and benefits deliver an ideal solution for many applications where traditional flooded batteries would not deliver the best results. For almost three decades, East Penn has been manufacturing valve-regulated batteries using tried and true technology backed by more than 65 years experience. EMS produces a complete line of Gel, AGM, and conventional flooded products for hundreds of applications. This diverse product offering enables EMS to be objective as to the advantages of each type of battery. EMS’s VRLA (Gel and AGM) products have the reputation of being the highest quality VRLA batteries available.

A VRLA battery utilizes a one-way, pressure-relief valve system to achieve a “recombinant” technology. This means that the oxygen normally produced on the positive plate is absorbed by the negative plate. This suppresses the production of hydrogen at the negative plate. Water (H2O) is produced instead, retaining the moisture within the battery. It never needs watering, and should never be opened as this would expose the battery to excess oxygen from the air. In addition to damaging the battery, opening it also voids the warranty.

Flooded electrolyte batteries do not have special one-way, pressure-relief valves, as they do not work on the recombination principle. Instead, flooded designs utilize a vent to allow gas to escape. They contain liquid electrolyte that can spill and cause corrosion if tipped or punctured. They should not be used near sensitive electronic equipment.

They can only be installed “upright.” Flooded batteries lose capacity and become permanently damaged if:

  • Left in a discharged condition for any length of time (due to sulfation). This is especially true of designs that require water maintenance.
  • Continually over-discharged (due to active material shedding). This is especially true of automotive starting types.

Deep Cycle, Deep Discharge Applications

  • Marine Trolling
  • Electronics
  • Sailboats
  • Electric Vehicles
  • Wheelchairs/Scooters
  • Golf Cars
  • Portable Power
  • Floor Scrubbers
  • Personnel Carriers
  • Renewable Energy
  • Village Power (Solar, Wind)
  • Marine & RV House Power
  • Commercial Deep Cycle Applications

Standby and Emergency Backup Applications

  • UPS (Uninterrupted Power Systems)
  • Cable TV
  • Emergency Lighting
  • Computer Backup
  • Renewable Energy
  • Frequency Regulation (Solar, Wind)
  • Telephone Switching

Other Applications

  • Race or High-Performance Cars
  • On-Highway Trucking
  • Off-Road Vehicles
  • Wet Environments
  • Marine & RV Starting
  • Diesel Starting
  • Cars and Light Trucks
  • Vehicles with Accessories
  • Start-Stop Systems

VRLA technology encompasses both gelled electrolyte or gel batteries and absorbed glass mat or AGM batteries. Both types are regulated by special one-way, pressure-relief valves and have significant advantages over flooded lead-acid products.

AGM (Absorbed Glass Mat) batteries

The electrolyte in AGM batteries is completely absorbed in separators consisting of matted glass fibers. This causes them to be spillproof, meaning they don’t leak acid like a flooded design if tipped on their side. The glass mats in AGM batteries are wrapped around the positive plate, which helps prevent damage from vibration and extend cycling. The battery’s groups are packed tightly in the case partitions also protecting its power producing components. AGM battery designs can have over twice the cycle life of a conventional flooded product in the right application.

Gel or Gelled Electrolyte batteries

The electrolyte in a Gel battery is permanently locked in a highly viscous gelled state instead of the traditional liquid form. Because there is no liquid-type electrolyte, it will not leak out of the battery if tipped on its side. The thick, gelled electrolyte and tightly packed groups also protect the battery’s power producing components. Gel battery designs have a superior deep discharge resiliency and can deliver over two to three times the cycle life of an AGM product in the right applications.

Batteries utilize special one-way, pressure-relief valves and must never be opened.

  • Requires no electrolyte maintenance unlike deep cycle flooded batteries that require frequent checking and adjustment of electrolyte levels.
  • Uses a recombination reaction to prevent the escape of hydrogen and oxygen gases normally lost in a flooded lead-acid battery (particularly in deep cycle applications).
  • Spillproof design enables installation in virtually any position (upside-down installation is not recommended).
  • Has a higher tolerance against damage from deep discharge. These batteries have optimized amounts of electrolyte (which is also referred to as “acid-starved”) so that they use the power in the acid before they use the power in the plates. This minimizes the destructive nature of ultra-deep discharges. Ultra-deep discharging is what causes plate shedding, which can destroy a battery.

A Gel battery is better suited for super-deep discharge applications, which means it can withstand deeper discharges without damaging the battery’s performance. However, due to the physical properties of the gelled electrolyte, Gel battery power declines faster than an AGM battery as the temperature drops below 32ºF (0ºC). AGM batteries excel for high current, high power applications and in extremely cold environments. AGM batteries deliver a better dual purpose solution for a combination of starting and accessory power.

All lead-acid batteries release hydrogen from the negative plate and oxygen from the positive plate during charging. VRLA batteries have one-way, pressure-relief valves. Without the ability to retain pressure within the cells, hydrogen and oxygen would be lost to the atmosphere, eventually drying out the electrolyte and separators.

Voltage is electrical pressure (energy per unit of charge). Charge (ampere-hours) is a quantity of electricity. Current (amperes) is electrical flow (charging speed). A battery can only store a certain quantity of electricity. The closer it gets to being fully charged, the slower it must be charged. Temperature also affects charging. If the right voltage is used for the temperature, a battery will accept charge at its ideal rate. If too much voltage is used, charge will be forced through the battery faster than it can be stored.

Reactions other than the charging reaction also occur to transport this current through the battery—mainly gassing. Hydrogen and oxygen may be given off faster than the recombination reaction. This raises the pressure until the one-way, pressure-relief valve opens. The gas lost cannot be replaced. Any VRLA battery will dry out and fail prematurely if it experiences excessive overcharging.

Note: It is too much voltage that initiates this problem, not too much charge — a battery can be “over-charged” (damaged by too much voltage) even though it is not fully “charged.” Never install any lead-acid battery in a sealed container or enclosure. Hydrogen gas must be allowed to escape.

In many respects, undercharging is as harmful as overcharging. Keeping a battery in an undercharged condition allows the positive grids to corrode and the plates to shed, dramatically shortening life. Also, an undercharged battery must work harder than a fully charged battery, which contributes to short life as well.

An undercharged battery has a greatly reduced capacity. It may easily be inadvertently over-discharged and eventually damaged.

One of the major disadvantages of nickel-cadmium (Ni-cad) batteries is that after shallow discharge cycles, the unused portions of the electrodes “remember” the previous cycles and are unable to sustain the required discharge voltage beyond the depth of the previous cycles. The capacity is lost and can only be restored by slowly discharging completely (generally outside the application), and properly recharging. VRLA lead-acid batteries do not exhibit this capacity robbing effect known as memory.

Although all valve-regulated batteries have the electrolyte immobilized within the cell, the electrical hazard associated with batteries still exists. Work performed on these batteries should be done with the tools and the protective equipment listed below. Valve-regulated battery installations should be supervised by personnel familiar with batteries and battery safety precautions.

Protective Equipment
To assure safe battery handling, installation and maintenance, the following protection equipment should be used:

  • Safety glasses or face shield (Consult application specific requirements)
  • Acid-resistant gloves
  • Protective aprons and safety shoes
  • Proper lifting devices
  • Properly insulated tools


Consult user manual of specific application for safety & operating requirements. The following safety procedures should be followed during installation: (Always wear safety glasses or face shield.)

  1. These batteries are sealed and contain no free flowing electrolyte. Under normal operating conditions, they do not present any acid danger. However, if the battery jar, case, or cover is damaged, acid could be present. Sulfuric acid is harmful to the skin and eyes. Flush affected area with water immediately and consult a physician if splashed in the eyes. Consult MSDS for additional precautions and first aid measures.
  2. Prohibit smoking and open flames, and avoid arcing in the immediate vicinity of the battery.
  3. Do not wear metallic objects, such as jewelry, while working on batteries. Do not store un-insulated tools in pockets or tool belt while working in vicinity of battery.
  4. Keep the top of the battery dry and clear of all tools and other foreign objects.
  5. Provide adequate ventilation as regulated by Federal, State and Local codes and follow recommended charging voltages.
  6. Extinguishing media: Class ABC extinguisher. Note: CO2 may be used but not directly on the cells due to thermal shock and potential cracking of cases.
  7. Never remove or tamper with pressure-relief valves. Warranty void if vent valve is removed.

NO! Never install any type of battery in a completely sealed container. Although most of the normal gasses (oxygen and hydrogen) produced in a VRLA battery will be recombined and not escape, oxygen and hydrogen will escape from the battery in an overcharge condition (as is typical of any type battery).

These potentially explosive gasses must be allowed to vent to the atmosphere and must never be trapped in a sealed battery box or tightly enclosed space!

Yes! The harder any battery has to work, the sooner it will fail.

The shallower the average discharge, the longer the life. It’s important to size a battery system to deliver at least twice the energy required, to assure shallow discharges.

Follow these tips for the longest life:

  • Avoid ultra-deep discharges. The definition of ultra-deep discharge may vary with application and battery type.
  • Don’t leave a battery at a low stage of charge for an extended length of time. Charge a discharged battery as soon as possible.
  • Don’t cycle a battery at a low state of charge without regularly recharging fully.

Use the highest initial charging current available (up to 30% of the 20-hour capacity per hour) while staying within the proper temperature-compensated voltage range.

The appropriate charge voltage depends on the battery temperatures. A warmer battery requires a reduced voltage. If the voltage is not reduced, current accepted by the battery increases. When the current increases, the internal heating increases. This can rise to destructive levels if not taken into consideration.

Thermal runaway can be prevented with:

  • Temperature compensation monitoring at the battery —not at the charger.
  • Limiting charging currents to appropriate levels.
  • Allowing for adequate air circulation around the batteries.
  • Using timers or ampere-hour counters.
  • Using smart chargers that recognize the signature of a thermal runaway event which will shut the charger down.