Frequently Asked Questions
Questions About Custom Battery Packs
Q. What is involved in getting a custom battery pack designed?
A. Alexander Battery Technologies has experienced Project Managers and Technical staff that will work with you through every stage – from Specification to Production - keeping you aware of costs and timescale throughout. Please call 641-423-8955 in the USA or +44 (0) 191 587 2787 in Europe for quick and experienced responses to your questions.
Q. What is the typical lead time to develop a custom battery pack?
A. Every battery pack is different – but Alexander Battery Technologies minimizes your time to market by leveraging your packs design from an extensive pool of design experience. Our customers’ requirements range from simple fast-turn projects of only a few weeks to complex and challenging projects with custom tooling and extensive regulatory requirements – this is where we excel as we can flex our approach to meet your project deadlines.
Q. How much would my custom battery pack cost?
A. Alexander Battery Technologies' target is to provide you a cost estimate within two weeks. We manufacture battery packs for many well-known OEM’s, and providing you can describe your performance requirements and production volumes, we can offer you a number of approaches to the design with varying costs for you to select the approach that works for you. There is usually a trade-off between cost, timescale and NREs – but we never compromise on safety and quality. Some considerations we will discuss with you are:
- Cell selection
- Number and configuration of cells needed to meet your electrical requirements
- Charge/Discharge requirements of your application
- Environmental considerations (temperature., humidity, where it's being used, etc)
- Pack enclosure options
- Testing and Certifications required for your application (UL, CE, ATEX, IATA UN38.3)
- There are many other factors as well. To help you develop a scope of your battery pack project please contact our experts for more guidance.
Q. What is the difference between a Cylindrical Cell, Prismatic cell, Pouch cell, and a Polymer cell?
A. Cylindrical cell refers to a battery cell that has the shape of a cylinder. The cans are typically rigid and metallic. The can may be stainless steel, aluminum, or steel. The cells will typically be vented at its positive end and may have a button top.
Prismatic cell: is battery cell that is rectangular in shape with a rigid metallic can. Furthermore, the chemistry will be a descriptive qualifier of the cell, i.e. NiMH prismatic, or Lithium Ion prismatic, etc.
Pouch cell: Commonly referred to as a Lithium Ion battery cell with a liquid electrolyte that is enclosed in a flexible, bag-shaped vessel that is sealed on its sides.
Polymer cell: A Polymer cell is similar to a Pouch cell; however, the key difference is that a Polymer cell uses a polymerized electrolyte whereas a Pouch cell will have a liquid electrolyte.
Q. What is the typical voltage cutoff when charging a Lithium Ion battery?
A. The maximum charge voltage is typically 4.2V per cell; however, for increased cycle life a lower cutoff can be utilized. Some newer LiIon cells emerging on the market may have a higher charge voltage (4.35V per cell) to increase the initial capacity of the cell, but the cycle life is typically lower with this type of cell.
Q. What is the typical cutoff voltage when discharging a Lithium Ion battery?
A. The discharge cutoff voltage of a Lithium Ion battery is 3.0V to 2.5V per cell. However, if increased cycle life is desired a slightly higher voltage cutoff can be utilized.
Q. What is the typical cutoff voltage for when charging and discharging a LiFePO4 (LiFe) battery?
A. The voltage of a LiFe battery is 3.2V per cell, slightly lower than a Lithium-Ion cell, therefore the charge and discharge cutoff voltages are also different than that of a Lithium Ion cell. The typical discharge cutoff voltage is 2.1-2.5V with 2.8V giving an increase in cycle life. The maximum charge voltage is 3.6-3.8V per cell.
PLEASE NOTE: The charge and discharge voltages of all LiIon Chemistries vary depending on temperature, exact chemistry composition of the cell, and the manufacturer specifications. Be sure to consult the experts at Alexander Battery Technologies and the cell manufactures' specifications for exact charge and discharge information.
Q. What is C-rate?
A. C-Rate describes the continuous discharge or charge rate in relation to the cell capacity
For example, discharging a 1 Amp hour cell at 1 amp would be a rate of 1 C, and will provide 1 hour of runtime.
Cells in parallel will allow for increased C-rates, however, safety circuit limitations may not allow for an increased charge or discharge rates
PLEASE NOTE: C-ratings from the cell manufacturer should be followed for safety and for best performance and depending on your requirements, our designs can manage this for you to ensure optimum performance is always achieved, and cell design parameters are not exceeded.
Q: What is the drain rate of a battery?
A. Drain rate is how rapidly energy is released from a battery. The drain rate is the speed at which its electrical charges are depleted. C/10, C, 2C, 3C are examples.
Different battery chemistries and cell types provide better drain rates than others. Example: LiIon Energy Cells will typically have more capacity but discharge at a lower rate than a LiIon Power Cell.
Q: What is battery self-discharge?
A: “Self-discharge” refers to the shelf-life of a primary cell or the rate of loss of charge in a rechargeable battery. A battery is said to be “end of life” when the battery cannot deliver at 60 to 80% of its manufacturer's rated capacity, depending on the battery type and chemistry.
Primary cells can last for several years in proper storage at room temperature.
Rechargeable batteries will lose their charge while being stored:
Lithium-Ion batteries are best stored at a partial state of charge (30-50%), and self-discharge about 2-4% every month
NiMH batteries can lose their charge in three to four weeks
PLEASE NOTE: Batteries stored at higher than ambient temperatures during storage will significantly reduce the shelf life of all types and chemistries batteries.
Q: What is a battery’s charge rate?
For secondary, or rechargeable, batteries the charge rate refers to how long it takes to recharge a battery.
- Some NiMh cells (C/20 to C/30) are designed for float or trickle charges for “stand by” applications. A 14-hour charge (C/10) is “standard” for NiMH batteries.
- Seven-hour fast charges are possible for most rechargeable chemistries.
- Li-ion, lithium polymer, and LiFe batteries typically may require up to 3 hours to completely charge to 100%.
Q: Does temperature affect batteries?
Absolutely! Temperature does indeed affect the performance of a battery and it should be a major design consideration when selecting a cell for your battery pack. Batteries do not function well at low temperatures, and high temperatures are negative to self-discharge.
- Most batteries perform best in the 20° to 60°C (68° to 140°F) range.
- Special “high temp” LiIon and NiMh cells are available that are designed to perform at higher temperatures.
Q: Why are LiIon batteries shipped at 30% charge level?
As of April 2016, the IATA Regulations UN38.3 requires that all LiIon batteries be transported at a state of charge (SOC) of no more than 30%. For more information on the shipping of LiIon battery packs please contact our battery experts.
For information about Battery Care and Maintenance please refer to this page.