Here are some of the most common questions that we are asked. Some are easy to answer in full, whilst others can only be addressed in general within this section. Our aim is to help you toward identifying the right solutions for you.

Approvals (6)

The approval for standard off the shelf batteries is usually already taken care of. Manufacturers like Enersys or GNB (Exide) for example, which we work with closely, have all the approvals you require to market your products anywhere in the World.

Additional approvals are only generally required when you are using a series of standard cells to make a new type of battery pack.

Lithium cells are always combined with a Protection Circuit Module (PCM) and usually also require leads and a connector to be attached to the PCM to attach to your product. It is also quite common to add thermal protection (either a PTC or NTC resistor, or sometimes both)

With so many different component parts and each being dependent upon your power requirements it is quite unusual to find a fully approved battery pack that fits your needs exactly.

By working with Freeway at the initial point of defining a battery specification we can give you a series of options. We will always try to offer combination of component parts that are already UL approved.

We always try to match UL approved cells to your requirements. Cells are approved to UL1642.

However, even if cells are approved the battery pack (including circuit protection and interconnect) will still need to go through UL2054 Approval to be considered UL approved for North American sales

We have direct links with UL in both Asia and Europe.  Working with both sites has really helped us to understand the processes more and we can pass on this experience to you.

The result is a smoother path to approval with minimised costs and time-line.

You will probably already be in discussions with, or have employed, an approvals specialist.  We can also help you through our manufacturing partners, who have experience that can be passed on to you.

Battery Basics (19)

An electric battery is a device consisting of one or more electrochemical cells that convert stored chemical energy into electrical energy. Each cell contains a positive terminal, or cathode, and a negative terminal, or anode. Electrolytes allow ions to move between the electrodes and terminals, which allows current to flow out of the battery to perform work..

Batteries are not 100% efficient – some energy is lost as there are heat and chemical reactions when charging and discharging. If you use 1000 watts from a battery, it might take 1200 watts or more to fully recharge it. Slower charging and discharging rates are more efficient. A battery rated at 180 amp-hours if charged and discharged over 6 hours might be rated at 220 AH at the 20-hour charge/ discharge rate and 260 AH at the 48-hour rate.

A primary battery is a battery that can only be discharged once and is not rechargeable.

A secondary battery is a rechargeable battery that can be charged and discharged many times.

Primary batteries, or primary cells, can produce current immediately on assembly. These are most commonly used in portable devices that have low current drain, are used only intermittently, or are used well away from an alternative power source, such as in alarm and communication circuits where other electric power is only intermittently available. Disposable primary cells cannot be reliably recharged and should be disposed of once drained.

In general, these have higher energy densities than rechargeable batteries, but disposable batteries do not fare well under high-drain applications.

Common types of disposable batteries include zinc–carbon batteries and alkaline batteries.

A rechargeable battery, storage battery, or accumulator is a type of electrical battery. It comprises one or more electrochemical cells, and is a type of energy accumulator used for electrochemical energy storage. It is technically known as a secondary cell because its electrochemical reactions are electrically reversible.

Rechargeable batteries come in many different shapes and sizes, ranging from button cells to megawatt systems connected to stabilise an electrical distribution network.

Rechargeable batteries have a lower total cost of use and environmental impact than disposable batteries. Some rechargeable battery types are available in the same sizes as common consumer disposable types. Rechargeable batteries have a higher initial cost but can be recharged inexpensively and reused many times.

A battery’s capacity is the amount of electric charge it can deliver at the rated voltage. The more electrode material contained in the cell the greater its capacity. A small cell has less capacity than a larger cell with the same chemistry, although they develop the same open-circuit voltage.Capacity is measured in units such as amp-hour (Ah).

The rated capacity of a battery is usually expressed as the product of 20 hours multiplied by the current that a new battery can consistently supply for 20 hours at 68 °F (20 °C), while remaining above a specified terminal voltage per cell. For example, a battery rated at 100 Ah can deliver 5 Amps over a 20-hour period at room temperature.

The cycle life of a battery is the number of times a battery can be charged and discharged before performance reduces to a level considered to be no longer within specification in terms of its charge capability and performance.

The C-rate is the multiple of the current over the current that a battery can sustain for one hour. A rate of 1 C means that an entire 1.6Ah battery would be discharged in one hour at a discharge current of 1.6 A. A 2C rate would mean a discharge current of 3.2 A, over one half-hour.

Disposable batteries typically lose 8 to 20 percent of their original charge per year when stored at room temperature (20°–30 °C). This is known as the “self-discharge” rate, and is due to non-current-producing “side” chemical reactions that occur within the cell even when no load is applied. The rate of side reactions is reduced for batteries are stored at lower temperatures, although some can be damaged by freezing.

Yes – old rechargeable batteries self-discharge more rapidly than disposable alkaline batteries, especially nickel-based batteries; a freshly charged nickel cadmium (NiCd) battery loses 10% of its charge in the first 24 hours, and thereafter discharges at a rate of about 10% a month. However, newer low self-discharge nickel metal hydride (NiMH) batteries and modern lithium designs display a lower self-discharge rate (but still higher than for primary batteries).

True memory effect is specific to sintered-plate nickel-cadmium cells. If a Ni-CD battery is only partially discharged (to 25% of capacity for example) and is then recharged, and this is repeated often, then the battery can behave like a fully discharged battery at the level at which it is usually put back on charge (in this example 25%).

Yes – there are two methods to remove the effect: firstly deep discharge at trickle current (i.e. 0.1C to 0V), secondly several full charge and discharge cycles at high currents (e.g. 1C).

Yes. A common process often mistaken for memory effect is voltage depression. In this case the peak voltage of the battery drops more quickly than normal as it is used, even though the total energy remains almost the same. In modern electronic equipment that monitors the voltage to indicate battery charge, the battery appears to be draining very quickly. To the user it appears the battery is not holding its full charge, which seems similar to memory effect. This is a common problem with high-load devices such as digital cameras.

Voltage depression is caused by repeated over-charging of a battery, which causes the formation of small crystals of electrolyte on the plates. These can clog the plates, increasing resistance and lowering the voltage of some individual cells in the battery. This causes the battery as a whole to seem to discharge rapidly as those individual cells discharge quickly and the voltage of the battery as a whole suddenly falls. This effect is very common, as consumer trickle chargers typically overcharge.

Li-ion (Lithium Ion). This is one of the newest cell types available. It is also the lightest battery type currently available on a commercial basis and can provide more power than the other main cell types. There are no known problems of memory effect with this battery type and it is the easiest battery type to care for. The downside of this battery is that it has the highest engineering costs and therefore the price is usually considerably higher than other cell types.

Typically, the individual cells in a battery have somewhat different capacities and may be at different levels of state of charge(SOC). Without redistribution, discharging must stop when the cell with the lowest capacity is empty (even though other cells are still not empty); this limits the energy that can be taken from and returned to the battery. By matching batteries at point of manufacture a set of batteries with similar characteristics can be grouped. This minimises the potential for unbalanced cells in a battery pack and ensures strong performance.

Battery balancing and battery redistribution refer to techniques that maximize a battery’s capacity to make all of its energy available for use and increase the battery’s lifetime. A battery balancer or battery regulator is a device in a battery packthat performs battery balancing. Balancers are often found in Lithium ion battery packs for cell phones and laptop computers. They can also be found in battery electric vehicle battery packs.

A full battery management system (BMS) might include active balancing as well as temperature monitoring, charging, and other features to maximize the life of a battery pack. In the vast majority of applications it is more cost effective to match cells at point of production. A BMS will make the battery last longer, but in most applications a matched cell approach is good enough and much more cost effective.

Battery Charging (3)

Battery balancing and battery redistribution refer to techniques that maximize a battery’s capacity to make all of its energy available for use and increase the battery’s lifetime. A battery balancer or battery regulator is a device in a battery packthat performs battery balancing. Balancers are often found in Lithium ion battery packs for cell phones and laptop computers. They can also be found in battery electric vehicle battery packs.

A battery charger or recharger is a device used to put energy into a secondary cell or rechargeable battery by forcing an electric current through it.

Different types of batteries can be matched with different type of battery charger.

The charging protocol depends on the size and type of the battery being charged. Some battery types have high tolerance for overcharging and can be recharged by connection to a constant voltage source or a constant current source; simple chargers of this type require manual disconnection at the end of the charge cycle, or may have a timer to cut off charging current at a fixed time. Other battery types cannot withstand long high-rate over-charging; the charger may have temperature or voltage sensing circuits and a microprocessor controller to adjust the charging current, and cut off at the end of charge

A Simple Charger

A simple charger works by supplying a constant DC or pulsed DC power source to a battery being charged. The simple charger does not alter its output based on time or the charge on the battery. This simplicity means that a simple charger is inexpensive, but there is a tradeoff in quality. Typically, a simple charger takes longer to charge a battery to prevent severe over-charging. Even so, a battery left in a simple charger for too long will be weakened or destroyed due to over-charging. These chargers can supply either a constant voltage or a constant current to the battery.

Trickle Chargers

A trickle charger is typically a low-current (5–1,500 mA) battery charger. A trickle charger is generally used to charge small capacity batteries (2–30 Ah). These types of battery chargers are also used to maintain larger capacity batteries (> 30 Ah) that are typically found on cars, boats, RVs and other related vehicles. In larger applications, the current of the battery charger is sufficient only to provide a maintenance or trickle current (trickle is commonly the last charging stage of most battery chargers). Depending on the technology of the trickle charger, it can be left connected to the battery indefinitely. Some battery chargers that can be left connected to the battery without causing the battery damage are also referred to as smart or intelligent chargers.

Timer Based Chargers

The output of a timer charger is terminated after a pre-determined time. Timer chargers were the most common type for high-capacity Ni-Cd cells in the late 1990s for example (low-capacity consumer Ni-Cd cells were typically charged with a simple charger).

Intelligent Chargers

The output current of a smart charger depends upon the battery’s state. An intelligent charger may monitor the battery’s voltage, temperature or time under charge to determine the optimum charge current and to terminate charging.

A typical intelligent charger fast-charges a battery up to about 85% of its maximum capacity in less than an hour, then switches to trickle charging, which takes several hours to top off the battery to its full capacity