Battery requirements capture
The important thing about getting what you want is knowing what you want!
All pretty straightforward, and if you are designing a new bit of kit, and want a battery for it, you will probably think a few key performance markers will be all that is required. You would be surprised at how often a battery is specified by voltage alone, or sometimes even just the space envelope. There are occasions where these single main requirements are so important in a design that they swamp the need to examine and specify other parameters. It is all too easy to focus on one design defining factor and lose sight of all the things that go to make up a battery that adds value to a successful design. If your battery falls short of the performance you thought it would give you because of a parameter you had not realised was important, and failed to identify it in your requirements specification (you did prepare one didn’t you?), how do you think the battery supplier will respond when you go back and tell them the battery design they advised you on is not good enough?
It is always worth preparing a requirements specification for the battery. It provides the details of what you need and helps a potential supplier come up with the best power solution for your device. Being able to ask the same question of multiple suppliers will put you in a superior position when choosing who your supplier is going to be. It will also help clarify in your mind what are the must haves are and the performance goals you can be more flexible with. Ultimately the requirements specification will be key in determining which power solution gives the best value.
So what do you need to include in your requirements spec?
This will vary depending on application, and this is where taking on some expert help is advisable if you are unsure. Broadly speaking, the main categories are;
Physical Parameters : Such as dimensions and mass but also electrical connector and case material, especially if not entirely housed within the host equipment.
Electrical Parameters : Basics are the energy required from the battery related to voltage and temperature, power demand also with reference to temperature – but other factors may need inclusion depending on the complexity of the requirement.
Added Features : Such as state of health & state of charge information and how this is displayed to the user.
Environmental: Vibration, shock, acceleration, immersion are examples of things that may need to be considered. In some cases electro magnetic compatibility may need consideration.
Safety : Certain applications may require a battery that is designed with added layers of safety. Protection against inadvertent charging, especially if there is both a rechargeable and non-rechargeable battery option for the equipment. These are examples of things that require addressing at the battery design stage.
Operational Use : Will the battery be stored for lengthy periods of time when not in use? If so, under what conditions? If the battery is going to be stored for many years, what are the minimum performance requirements?
Transportation : Certain types of battery have restrictions placed on them regarding methods of transportation as well as added regulation. Knowing that frequent movement by air (for example) is required, enables the battery designer address this avoiding potential delays and extra costs later.
Through Life Issues : Equipment disposal and obsolescence management for example.
As well as a section covering specifics relating to your project!
Information under each heading above is only an indication of the type of data required, and for some parameters can be quite complex. Of course there may be no specific requirement for some of these categories at all, just asking yourself the question is sometimes enough to know it has been addressed. The difficulty is knowing when the information you think is irrelevant is actually quite important to battery function, for example if a particular cell type behaves differently depending on its orientation. In this case if you know that your kit is required to be used for long periods of time inverted, there may be some cell types that are unsuitable!
If this seems a bit daunting, don’t panic. Enlisting the help of an independent battery expert who can guide you through the creation of a battery requirements specification will enable you to address those categories that need inclusion whilst omitting those that don’t. The result – cost effective battery selection and a gold star for battery selection!
For further information please contact me at firstname.lastname@example.org or use the contact form on the website.