Choosing a battery for your application is often overlooked, and left until the very end of the product design cycle. Often the product will grow during development and fill ever increasing amounts of a maximum size envelope. Finally the space remaining is devoted to powering the unit and the disappointment sets in after initial conversations with your chosen battery pack manufacturer.
Involving a knowledgeable battery pack manufacturer early will help ensure that the product lives up to your marketing teams expectations as you move into full production. Furthermore correct battery selection made early will have other ramifications that must be understood clearly.
Primary or secondary is the first choice, or in layman’s terms single use or rechargeable. Both have their place and obvious benefits and drawbacks.
|Primary (single use) battery||Secondary (rechargeable) battery|
|High energy density (lots of energy for a given size)||Lower energy density (less energy in a given size)|
|Low continuous current capability||High continuous current capability|
|Very low self discharge (natural capacity loss of the cell over time). A few percent of capacity annually.||Some self discharge, varies according to the cell type. Li-ion around 3% per month, others as much as 20% per month.|
|Affordable but has to be replaced each time||More expensive but recharges many times. Remember to factor cost of charger into calculations.|
|Simple, usually doesn’t need electronics to function||More complex, often requires electronic circuits integrated into the battery to be safe and add capacity information capability (nb. Lithium batteries always require an electronic safety circuit)|
Self discharge is a term used to describe the energy that is lost from a battery over time with no useful work being done by it. A battery stored on a shelf, disconnected from all apparatus will over time deplete itself ultimately to a point where no useful energy is left within it. The self discharge of a particular battery is also affected by its initial state of charge (how full), the temperature it is stored
Examples of the two battery types are numerous, examples of common packs follow.
Primary – GPS tracking devices, electronic tags, flow metering instruments (water/gas/oil etc), subsea monitoring etc. You’ll also know them from watches, hearing aids, childrens toys, torches etc. Essentially if the product requires a low amount of power and usually for a long period of time, often primary batteries are the right choice. It may be that the equipment battery is remote or in environmentally difficult conditions, often this means a long life is paramount because of difficulties replacing them.
Secondary – Everything that plugs in to recharge, laptops, medical devices, cars, emergency lighting, PPE equipment, scooter, e-bikes, cars and so on. These applications tend to need a lot more power but don’t usually need so much run time before they can be recharged.
Once an understanding of what is required at this high level, more detail can be gone into to further nuance what is actually the right solution for the application. Each type of battery has many chemistry groups within it e.g. alkaline, zinc carbon, silver oxide, lead-acid, lithium, nickel metal cadmium, lithium ion, lithium thionyl chloride, lithium iron phosphate (or ferrophosphate) and so it goes on. Creasefield builds batteries using all these types, every application is different and each chemistry has strengths and weaknesses that must be understood and considered before a design decision is made.
The earlier you can involve your chosen battery pack builder, the better the outcome of getting the right solution for your energy supply need.