Accumulator - A rechargeable battery or cell (see also Secondary battery).
Ampere or Amp - An Ampere or an Amp is a unit of measurement for an electrical current. One amp is the amount of current produced by an electromotive force of one volt acting through the resistance of one ohm. Named for the French physicist Andre Marie Ampere. The abbreviation for Amp is A but its mathematical symbol is "I". Small currents are measured in milli-Amps or thousandths of an Amp.
Amp Hour or Ampere-Hour - One amp hour is equal to a current of one ampere flowing for one hour. Also, 1 amp hour is equal to 1,000 mAh
Anode - The negative electrode of a cell. The anode gives up electrons to the load circuit and dissolves into the electrolyte.
Aqueous Batteries - Batteries with water-based electrolytes. The electrolyte may not appear to be liquid since it can be absorbed by the battery's separator.
Actual Capacity or Available Capacity - The total battery capacity, usually expressed in ampere-hours or milliampere-hours, available to perform work. The actual capacity of a particular battery is determined by a number of factors, including the cut-off voltage, discharge rate, temperature and method of charge and the life history of the battery.
Battery - An electrochemical device used to stores energy. The term is usually applied to a group of two or more electric cells connected together electrically. In common usage, the term "battery" is also applied to a single cell, such as a AA battery.
Battery Capacity - The electric output of a cell or battery on a service test delivered before the cell reaches a specified final electrical condition and may be expressed in ampere-hours, watt- hours, or similar units. The capacity in watt-hours is equal to the capacity in ampere-hours multiplied by the battery voltage.
Battery Charger - A device capable of supplying electrical energy to a battery.
Battery-Charge Rate - The current expressed in amperes (A) or milli amps (mA) at which a battery is charged.
Cutoff Voltage, final - The prescribed lower-limit voltage at which battery discharge is considered complete. The cutoff or final voltage is usually chosen so that the maximum useful capacity of the battery is realized. The cutoff voltage varies with the type of battery and the kind of service in which the battery is used. When testing the capacity of a NiMH or NiCD battery a cutoff voltage of 1.0 V is normally used. 0.9V is normally used as the cutoff voltage of an alkaline cell. A device that is designed with too high a cutoff voltage may stop operating while the battery still has significant capacity remaining.
C - Used to signify a charge or discharge rate equal to the capacity of a battery divided by 1 hour. Thus C for a 1600 mAh battery would be 1.6 A, C/5 for the same battery would be 320 mA and C/10 would be 160 mA. Because C is dependent on the capacity of a battery the C rate for batteries of different capacities must also be different.
Capacity - The capacity of a battery is a measure of the amount of energy that it can deliver in a single discharge. Battery capacity is normally listed as amp-hours (or milli amp-hours) or as watt-hours.
Cathode - The positive electrode of a voltaic cell. The electrode that, in effect, oxidizes the anode or absorbs the electrons.
Cell - An electrochemical device, composed of positive and negative plates and electrolyte, which is capable of storing electrical energy. It is the basic "building block" of a battery.
Charge Rate - The amount of current applied to battery during the charging process. This rate is commonly expressed as a fraction of the capacity of the battery. For example, the C/2 or C/5.
Charging - The process of supplying electrical energy for conversion to stored chemical energy.
Constant-Current Charge - A charging process in which the current applied to the battery is maintained at a constant value.
Constant-Voltage Charge - A charging process in which the voltage applied to a battery is held at a constant value.
Cycle - One sequence of charge and discharge.
Deep Cycle - A cycle in which the discharge is continued until the battery reaches it's cut-off voltage.
Shallow Cycling - Charge and discharge cycles which do not allow the battery to approach it's cutoff voltage. Shallow cycling of NiCd cells lead to "memory effect". Shallow cycling is not detrimental to NiMH cells and it is the most beneficial for lead acid batteries.
Cycle Life - For rechargeable batteries, the total number of charge/discharge cycles the cell can sustain before it's capacity is significantly reduced. End of life is usually considered to be reached when the cell or battery delivers only 80% of rated ampere- hour capacity. NiMH batteries typically have a cycle life of 500 cycles, NiCd batteries can have a cycle life of over 1,000 cycles. The cycle of a battery is greatly influenced by the type depth of the cycle (deep or shallow) and the method of recharging. Improper charge cycle cutoff can greatly reduce the cycle life of a battery.
Discharge - The conversion of the chemical energy of the battery into electric energy.
Depth of Discharge - The amount of energy that has been removed from a battery (or battery pack). Usually expressed as a percentage of the total capacity of the battery. For example, 50% depth of discharge means that half of the energy in the battery has been used. 80% DOD means that eighty percent of the energy has been discharged, so the battery now holds only 20% of its full charge.
Discharge, deep - Withdrawal of all electrical energy to the end-point voltage before the cell or battery is recharged.
Discharge, high-rate - Withdrawal of large currents for short intervals of time, usually at a rate that would completely discharge a cell or battery in less than one hour.
Discharge, low-rate - Withdrawal of small currents for long periods of time, usually longer than one hour.
Drain - Withdrawal of current from a cell.
Dry Cell - A primary cell in which the electrolyte is absorbed in a porous medium, or is otherwise restrained from flowing. Common practice limits the term "dry cell" to the Leclanch, cell, which is the common commercial type.
Electrochemical Couple - The system of active materials within a cell that provides electrical energy storage through an electrochemical reaction.
Electrode - An electrical conductor through which an electric current enters or leaves a conducting medium, whether it be an electrolytic solution, solid, molten mass, gas, or vacuum. For electrolytic solutions, many solids, and molten masses, an electrode is an electrical conductor at the surface of which a change occurs from conduction by electrons to conduction by ions. For gases and vacuum, the electrodes merely serve to conduct electricity to and from the medium.
Electrolyte - A chemical compound which, when fused or dissolved in certain solvents, usually water, will conduct an electric current. All electrolytes in the fused state or in solution give rise to ions which conduct the electric current.
Electropositivity - The degree to which an element in a galvanic cell will function as the positive element of the cell. An element with a large electropositivity will oxidize faster than an element with a smaller electropositivity.
End-of-Discharge Voltage - The voltage of the battery at termination of a discharge.
Energy - Output Capability - expressed as capacity times voltage, or watt-hours.
Energy Density - Ratio of cell energy to weight or volume (watt-hours per pound, or watt-hours per cubic inch).
Final Voltage (see Cutoff voltage)
Float Charging - Method of recharging in which a secondary cell is continuously connected to a constant-voltage supply that maintains the cell in fully charged condition. Typically applied to lead acid batteries.
Galvanic Cell - A combination of electrodes, separated by electrolyte, that is capable of producing electrical energy by electrochemical action.
Gassing - The evolution of gas from one or both of the electrodes in a cell. Gassing commonly results from self-discharge or from the electrolysis of water in the electrolyte during charging.
Internal Resistance - The resistance to the flow of an electric current within the cell or battery.
Memory Effect - A phenomenon in which a cell, operated in successive cycles to less than full, depth of discharge, temporarily loses the remainder of its capacity at normal voltage levels (usually applies only to Ni-Cd cells). Note, memory effect can be will be induced in NiCd cells even if the level of discharge is not the same during each cycle. Memory effect is reversable.
Negative Terminal - The terminal of a battery from which electrons flow in the external circuit when the cell discharges. See Positive Terminal.
Nonaqueous Batteries - Cells that do not contain water, such as those with molten salts or organic electrolytes.
Ohm's Law - The formula that describes the amount of current flowing through a circuit. Ohm's Law - In a given electrical circuit, the amount of current in amperes (I) is equal to the pressure in volts (V) divided by the resistance, in ohms (R). V=I/R
Open Circuit - Condition of a battery which is neither on charge nor on discharge (i.e., disconnected from a circuit).
Open-Circuit Voltage - The difference in potential between the terminals of a cell when the circuit is open (i.e., a no-load condition).
Oxidation - A chemical reaction that results in the release of electrons by an electrode's active material.
Parallel Connection - The arrangement of cells in a battery made by connecting all positive terminals together and all negative terminals together. The voltage of the group remains the same as the voltage of the individual cell. The capacity is increased in proportion to the number of cells.
Polarity - Refers to the charges residing at the terminals of a battery.
Positive Terminal - The terminal of a battery toward which electrons flow through the external circuit when the cell discharges. See Negative Terminal.
Primary Battery - A battery made up of primary cells. See Primary Cell.
Primary Cell - A cell designed to produce electric current through an electrochemical reaction that is not efficiently reversible. The cell, when discharged, cannot be efficiently recharged by an electric current. Alakline, lithium, and zinc air are common types of primary cells.
Rated Capacity - The number of ampere-hours a cell can deliver under specific conditions (rate of discharge, end voltage, temperature); usually the manufacturer's rating.
Rechargeable - Capable of being recharged; refers to secondary cells or batteries.
Recombination - State in which the gases normally formed within the battery cell during its operation, are recombined to form water.
Reduction - A chemical process that results in the acceptance of electrons by an electrode's active material.
Seal - The structural part of a galvanic cell that restricts the escape of solvent or electrolyte from the cell and limits the ingress of air into the cell (the air may dry out the electrolyte or interfere with the chemical reactions).
Secondary Battery - A battery made up of secondary cells. See Storage Battery; Storage Cell.
Self Discharge - Discharge that takes place while the battery is in an open-circuit condition.
Separator - The permeable membrane that allows the passage of ions, but prevents electrical contact between the anode and the cathode. Series
Connection - The arrangement of cells in a battery configured by connecting the positive terminal of each successive cell to the negative terminal of the next adjacent cell so that their voltages are cumulative. See Parallel Connection.
Shelf Life - For a dry cell, the period of time (measured from date of manufacture), at a storage temperature of 21 degrees C (69 degrees F), after which the cell retains a specified percentage (usually 90%) of its original energy content.
Short-Circuit Current - That current delivered when a cell is short-circuited (i.e., the positive and negative terminals are directly connected with a low-resistance conductor).
Starting-Lighting-Ignition (SLI) Battery - A battery designed to start internal combustion engines and to power the electrical systems in automobiles when the engine is not running. SLI batteries can be used in emergency lighting situations.
Stationary Battery - A secondary battery designed for use in a fixed location.
Storage Battery - An assembly of identical cells in which the electrochemical action is reversible so that the battery may be recharged by passing a current through the cells in the opposite direction to that of discharge. While many non-storage batteries have a reversible process, only those that are economically rechargeable are classified as storage batteries. Synonym: Accumulator; Secondary Battery. See Secondary Cell.
Storage Cell - An electrolytic cell for the generation of electric energy in which the cell after being discharged may be restored to a charged condition by an electric current flowing in a direction opposite the flow of current when the cell discharges. Synonym: Secondary Cell. See Storage Battery.
Taper Charge - A charge regime delivering moderately high-rate charging current when the battery is at a low state of charge and tapering the current to lower rates as the battery becomes more fully charged.
Terminals - The parts of a battery to which the external electric circuit is connected.
Thermal Runaway - A condition whereby a cell on charge or discharge will destroy itself through internal heat generation caused by high overcharge or high rate of discharge or other abusive conditions.
Trickle Charging - A method of recharging in which a secondary cell is either continuously or intermittently connected to a constant-current supply that maintains the cell in fully charged condition.
Vent - A normally sealed mechanism that allows for the controlled escape of gases from within a cell.
Volt - The unit of electromotive force, or difference of potential, which will cause a current of one ampere to flow through a resistance of one ohm. Named for Italian physicist Alessandro Volta (1745-1827).
Voltage, cutoff - Voltage at the end of useful discharge. (See Voltage, end-point.)
Voltage, end-point - Cell voltage below which the connected equipment will not operate or below which operation is not recommended.
Voltage, nominal - Voltage of a fully charged cell when delivering rated current.
Wet Cell - A cell, the electrolyte of which is in liquid form and free to flow and move.
What's the difference between a rapid charger and a fast charger?
Both terms are essentially meaningless. There is no standard in the industry, so manufacturers can use the terms in different ways. One of the problems with terms like these is that the amount of time it takes to charge a battery is dependent on the capacity of the battery being charged. A charger that can charge a standard capacity AAA NiCD battery (180 mAh) in just one hour might take 8 hours to charge a high capacity NiMH (1500 mAh) battery. It's best to ignore such terms and make a rough calculation of how fast a charger can charge batteries. (To do this you How long will it take a charger to charge batteries?
It's pretty easy to estimate how long it will take. Simply divide the capacity of the battery by the charge rate of the charger, then increase the amount of time by about 20% to allow for a certain amount of inefficiency. As an example, a battery with a capacity of 1600 mAh will require about 4 hours to be fully charged by a charger with a charge rate of 500 mA. (1600 mAh/500 mA x120%). Incidentally, this example would apply to a standard AA NiMH battery and a typical "rapid charger". Keep in mind that a battery that is only partially discharged will be recharged in less time. Can a battery charger damage a battery (shorten its life or reduce its capacity)?
Yes. The most common cause of premature battery failure is overcharging. The type of chargers most likely to cause overcharging are the 5 or 8 hour so-called "rapid chargers". The problem with these chargers is that they really don't have a charge control mechanism. Most of them are simple designs which charge at their full charge rate for a fixed period of time, typically five or eight hours, and then shut off or switch to a lower "trickle" charge rate. If they are used properly, these chargers are fine. If they are used improperly they can shorten a battery's useful life in a couple of ways.
First; suppose fully charged or partially charged batteries are put into the charger. The charger has no way to sense this, so it will give the batteries the full charge it was designed to deliver. It is not unusual to put partially charged batteries into a charger since it's pretty easy to mix batteries up and inadvertently put fully charged batteries into a charger. Do this enough times with one of these battery chargers and the capacity of the battery will start to drop.
Another common situation is for the charge cycle to be interrupted part way through the charge. The charger is unplugged to see how warm the batteries feel or to use the electrical outlet for something else. Then the charger is plugged back in. Unfortunately, this will cause a complete charge cycle to start again, even if the previous charge cycle was almost complete.
The easiest way to avoid these scenarios is to use a smart charger, a charger with microprocessor control. A smart charger can determine when a battery is fully charged and then depending on its design, either shut off entirely or switch to trickle charge. Most of our chargers use microprocessor control. For s
What is trickle charge?
Theoretically a trickle charge is a charge rate that is high enough to keep a battery fully charged, but low enough to avoid overcharging. Maintenance charge is another way to describe trickle charge. Determining the optimum trickle charge rate for a particular battery is a bit tricky to describe but is generally accepted to be around ten percent of the battery capacity - i. e. Sanyo 2500 mAh AA NiMH optimum trickle charge rate is at or below 250mA. One of the reasons it is important for you to understand the optimum trickle charge rate for your charger and batteries is to compensate for the self discharge of NiCD and NiMH batteries. Another reason is because overcharging a battery will definitely reduce it's useful life. Although most manufacturers do not recommend that you leave a battery in the charger for long periods of time, many people leave their batteries in the charger on trickle charge for days or weeks to keep their batteries "ready to use". If you know the rate of trickle charge that your charger puts out and it is around one tenth of the battery capacity or less, then you should be alright if you are just going to do this occasionally. Generally speaking, though you do not want to leave a battery charger plugged in unattended for long periods of time.
Is trickle charging harmful to batteries? Many battery manufacturers do not recommend long term ( months at a time) trickle charging. If trickle charging is used then the charge rate should be very low or only intermittent. The best smart chargers will only send an occasional pulse charge to the battery once it is charged. They do not apply a continuous low rate of charge. Some battery resellers state that applying a continuous trickle charge of about 1/10th the battery's capacity is not harmful. However, we have not seen any battery manufacturer condone the practice. It is better to fully charge batteries and then store them fully charged in the freezer than to leave them on trickle charge for very extended periods of time.
Does rapid charging reduce the life of batteries?
Not significantly. So long as it is done using a properly designed smart charger, most NiMH batteries can be recharged in about an hour without any damage or significant reduction in their life. However, NiMH batteries must only be rapid charged with a charger specifically designed for charging NiMH batteries. Chargers designed to rapidly charge NiCd batteries can overcharge NiMH batteries. While it may be true that rapid charging NiMH batteries can reduce battery life by a small amount (probably less than 10%), this should be more than offset by the inconvenience of always slow charging batteries.
What's the difference between a NiMH battery charger and a NiCd battery charger.
The biggest differences are in the charge rate (how fast the charger can charge batteries) and the charge control (how the charge determines when to stop the charge). Many of the inexpensive NiMH battery chargers are simply NiCd chargers that have been modified slightly. Typically a 5 hour NiCd charger has a switch that allows the charge time to be increased from five hours to eight hours. Thus a 5 hour NiCd charger becomes an 8 hour NiMh charger. As we mentioned above, we do not recommend this type of charger design. While a timer type charger is less expensive to manufacture than a smart charger, it can lead to overcharging and battery damage if batteries are frequently charged before they have been discharged (that is, the batteries are used for a short time and then fully charged again). NiMH smart chargers have actually been designed to detect when a NiMH battery is fully charged and then shut off or go into a trickle charge mode. Because of the more complex circuitry, this type of charger costs more to make, but should lead to greater battery life. Some of these chargers only cost slightly more that the "dumb" chargers. We strongly recommend investing in a smart charger for your NiMH or NiCd batteries.
Can I use an older NiCd battery charger to charge NiMH batteries?
The answer to this question depends on the type of NiCd charger. Depending on the type of NiCd charger you have, the older NiCd charger may undercharge NiMH batteries (most likely), it may overcharge them (less likely), or it may charge NiMH batteries properly (but it's not likely to do so automatically and could take a very long time). Let's take a look at the three cases.
Many of the older NiCd chargers are the simple timed type charger which will charge batteries for a fixed amount of time and then shut off. Unfortunately, since NiCd batteries have a much lower capacity than NiMH batteries, the timer is likely to shut off long before the NiMH batteries are fully charged. This won't harm the batteries, but the NiMH batteries won't be fully charged since the timer will have stopped the charge cycle too soon.
Also common among older NiCd chargers are the so called "overnight" chargers which charge batteries at a low rate as long as the charger is plugged in. This type of charger can fully charge NiMH batteries, but it might take a very long time to do so. It's possible that an old NiCd charger could take as long as 48 hours to fully charge new high capacity NiMH batteries! This type of charger is not likely to damage NiMH batteries unless the batteries are left in the charger for weeks at a time.
The final possibility is that the older NiCd charger is a rapid charger that will charge NiMH batteries but will not have the necessary circuitry to stop the charge cycle once the NiMH batteries are fully charged. If the NiCd charger is designed to charge batteries in less than two hours it may be this type. In this case the risk is that the older charger will overcharge NiMH batteries. This will be apparent if the batteries get very hot during the charge cycle. (It is normal for NiMH batteries to get warm as they become fully charged, especially in a rapid charger). If the NiMH batteries get too hot to handle and stay that way for more than 20 or 30 minutes, then the NiCd charger is most likely overcharging the NiMH batteries and may shorten their life. You would be most likely to encounter this type of charger if the charger was designed for rapid charging radio control (RC) vehicle batteries. We would recommend that you not use an NiCD rapid charger to charge NiMH batteries.
Which are better, NiCD or NiMH batteries?
This really depends on what you are going to use them for exactly. NiCD batteries are commonly used for power tools and in that capacity they are in many ways superior to NiMH batteries. For high drain digital devices where weight is of primary importance, NiMH batteries are the best choice. NiMH batteries are also considered an environmentally friendly battery chemistry. NiCD's are toxic and recycling them is mandatory.
What is battery conditioning or exercising?
When you intentionally discharge a battery down to a certain minimum voltage and then recharge it this is known as battery conditioning or reconditioning . It is also sometimes referred to as battery exercise. This is particularly important to reduce what some call the memory effect experienced using NiCD batteries if you habitually do not fully discharge them each time you use them. For NiCD batteries this must be done periodically, approximately every 10 charge/discharge cycles or so, or the batteries will begin to lose capacity. For NiMH batteries conditioning is not really needed to reduce any memory effect because that is negligent in this type of battery. However, reconditioning is very convenient for both NiMH and NiCD batteries because brand new batteries are not charged when you receive them and they must be charged and discharged three to five times before they reach their full capacity. In addition, occasionally conditioning rechargeable batteries helps to ensure that they give you years or service and save you as much money as possible, before you recycle them and get new ones.
What is a charge channel or charge circuit?
Battery chargers have one or many charge channels aka charge circuits. Each charge channel can charge one or more than one battery. for example, it is common for a AA, and AAA battery charger to have four charge stations and two charge channels. This means that each charge channel charges two batteries in the same circuit. This is why you see lots of folks recommend that you keep your batteries in sets to optimize their charging. Mostly, this is recommended because you are probably using a charger that has two batteries in each charge channel, like our TurboCharger 4000 for example.
What is a charge station?
In a battery charger, the charge station is where you place the battery to recharge it. Many battery chargers have charge stations that accommodate multiple kinds and sizes of batteries. For example, most AA chargers will also accept AAA batteries, and some "universal" chargers will accept other kinds as well in the same charge station. e.g.- AA, AAA, C, and D cells. Still other kinds universal chargers have adapters that come included, or must be obtained separately, to use different kinds and sizes of batteries.
What makes a charger a "smart charger"?
Any charger that uses a computer chip to control various aspects of the charging process can be considered a smart charger. Technically even a charger that can detect and adjust the charge rate based on the battery inserted into the charge station can be considered a smart charger, but anything that is either manual (steady charge rate as long as it is plugged in) or uses a timer to manage the charging process, we do not consider a true smart charger. There are even various levels of smart chargers. Different features that work together, sometimes in mysterious ways because there are just so many variables with batteries and chargers. In order for us to consider a battery charger a smart charger it needs to have a common charging feature known as negative delta V. Negative delta V is basically a technical method for a charger to know when a battery has reached its charge capacity and then shut the charging off, or sometimes change to trickle charge mode. Other features that contribute to a battery chargers smart status are: temperature sensor, discharge and conditioning features, battery test features and even timers to limit the total length of the charge so even if you leave it plugged in, it turns itself off after a preset time.