Why I do this!

Apologies, but a bit of self indulgence in this months blog. Every now and then it is good to take stock and just reaffirm why I do what I do!

I offer a battery consultancy service allowing my clients to access my experience of over 36 years working with, and developing advanced battery solutions. Benefits include;

• Accurate battery type selection
• Improved product performance
• Superior integration of the battery into a system
• Selection of the best supplier
• Reduced costs

Having worked for one of the largest manufacturers of battery solutions in the UK for so long, I often found myself meeting clients who, although they had a good idea of what they wanted, did not know all of the options available to them. Of course, my advice had to be tailored to the product portfolio of my employer. It was very frustrating knowing that there were better options out there from other battery suppliers that, until now, I could not promote.

Most development and design engineers will have spent some time learning battery basics and followed this up with looking at the various articles available on the internet covering battery matters. That’s fine if the battery manufacturers are putting like for like data in their publicity. But they don’t. This makes comparing products very tricky.

Knowing how a particular battery responds to the loads and environments required, especially whilst you are still developing the product is tricky. Yes, a supplier will do some lifetime and performance calculations for you, but if the goal posts are moving as your product develops, they will not be as keen when you go back again and again asking for the calculations to be repeated. Of course they will do it with a smile on their face, but this activity has a cost, and you can be sure that it will be recovered eventually.

So how much more convenient it would be to have access to someone who can do these predictions for you before getting a potential supplier on board. Especially as you will know they are working for your interests and not those of the supplier.

I look forward to helping you in the future!

Careful thought needs to be given to the interaction of the battery, the device it is powering, the environment it is operating in and the skill set of the eventual user. The availability of ever more powerful and energetic batteries, and the rules and regulations regarding transport and disposal, mean that battery selection is not as straightforward as seems at first. The use of an independent expert to give guidance to your design team can save a huge amount of time and cost to new project development. If you are interested in finding out more, please contact DM Power Solutions using the contact form on this website.

#AskAnExpert

Finally it looks like we are at least having a little bit of summer here in the UK. After the summer so far everyone should be out there making the most of it. If your thing is lounging in a hammock with a cool drink, or energetically walking up as many hills as possible, the aim is the same: switch off from the workday grind and get on and clear the mind to be positive and creative for the challenges ahead.

 
But can you really switch off when your project is running late and you know that on your return there is a looming deadline? This is where a specialist can take the load of your mind. By identifying issues and having an expert come in a sort them out, you can go off on your holidays and chill out knowing that that irritating problem is being taken care of.

 
So don’t ruin your holiday by worrying about what awaits your return to the office. Free your mind to come up with something inspirational and let a subject expert do the hard graft for you!

 
Happy Holidays!

 

Costly Mistakes

I see that in the US there is yet another issue with the batteries in self balancing scooters (hoverboards) resulting in a large scale recall, somewhere over 500,000 is a figure being widely banded about. The problem is with scooters made before a new standard was introduced, which seems to be a boost for all those associated with the generation of industry standards.

 
Why the problem with batteries in these particular devices? After all, the technology is in effect the same as that used in your smartphone. Think of all the millions of hours of safe, reliable use the batteries in those devices have clocked up. The reality is that there is a big difference between the single cell battery typically used in smartphones and the multi cell packs designed for other applications.

 
Often it is the way cells are packaged into batteries, and then the enclosure in which they are located, that is overlooked at the design stage. Just assuming that you can link multiple cells into a series and/or parallel arrangements and multiply the cell level performance accordingly is a potential problem in the making. Add to this enclosing the battery in a sealed compartment with little or no air movement, and a high discharge rate, the risk of battery failure rises to a point that is unacceptable.

 
There is nothing inherently wrong with multi cell batteries. Provided the cells chosen are capable of the required discharge rate,  allowances made for de-rating as dictated by the way the battery is housed, a properly designed battery will provide reliable performance over the projected lifetime in a safe and user friendly manner.

 
Expecting your equipment designer to be a battery application expert is a big ask, especially with all the other details that need to be addressed. Having access to an independent battery expert will provide a cost effective solution to help avoid those common, and not so common, battery design and use errors.

 
For more information please email enquiries@dmpowersolutions.co.uk or use the form on the contacts page of this website.

Information Overload!

The day is almost here, it is make your mind up time. June 23rd seemed so far away at the start of the year yet now it is upon us.

It should be simple, only the one question to which you have a binary answer. The only options are ‘0’ or ‘1’. The problem is an almighty bundle of information being thrown out by supporters of whichever side of the argument they are on, often contradictory to what may or may not have been said before. It is inevitable that this information will be skewed in favour of the argument putting it forward, and what is seen as factual by one side is labelled misleading by another. Inevitably the average voter has more of a life to get on with than wading through all the argument and counter argument to come to a reasoned decision. It is difficult to remain balanced and make sure that there is a reasonable equality of both views being received. Everyone will have an opinion based on what the most important factors are to them, sovereignty, economy, immigration, security and so on and there will be a tendency to filter information based on personal importance at the risk of excluding other vital data.

What relevance does this have to a blog on a website about battery selection and design? Well, imagine how much easier it would be to make your referendum choice if you could talk to an expert who has a completely neutral opinion regarding the final result, they just advise on what the right result is for you. Someone that you could talk to about what is important to you and objectively look at what all the options are, and give you a straight, unbiased answer as to what you should logically decide. Then all that time you would have spent researching is yours again, to spend as you see most useful and productive to you.

Selecting the best battery type and configuration is just as complicated, if not more so with various manufacturers and distributors all vying for your business. Plus, with so many variables to consider, the potential to fog the argument concerning a parameter vital to your product is significant. What you need is a truly independent advisor who is working just to your requirements who can give you a straight call on which option is best for you.

Getting an advisor involved is simple and cost effective. Take the next step in selecting the best battery for your project now by filling in the simple contact form on the contacts page of this website, or send an email directly to enquiries@dmpowersolutions.co.uk asking for help.

As for the referendum question, good luck!

Understanding Battery Data Sheets

In the perfect world it would be possible to get all the information you need, and compare different manufacturers product, by referring to their data sheets. But this is not a perfect world, and battery manufacturers seem to have gone out of their way to make it difficult to compare like with like. Even product from the same manufacturer often does not include a consistent presentation of performance across their range of products.

 
If you are looking for general performance guidelines cell and battery data sheets are fine. A lot of effort goes into compiling them and making sure data is accurate. Data is normally presented for stand alone tests, at cell level this means a discharge curve is at a specific current under controlled conditions such as temperature and orientation. The test subject will be a cell that is no more than a couple of months old, and correct test methodology, such as separate current and voltage monitoring connections, will have been implemented. It is also likely that connections to the test cell are through resistance welded tabs, especially for higher current tests.

 
Sometimes there may be some representation of pulse capability, where a higher current pulse is superimposed on a low base load. Again, this is useful general information on how a specific cell will perform, but quite minor changes from the load profile presented are likely to give different results.

 
The use of data presented on charts with logarithmic scales gives the opportunity to present lots of data in a relatively compact form. But as always, the devil is in the detail. Having a chart that shows performance at -20, +20, +40 and +60°C is not much good if you want to know what happens at +5°C. This is a particular problem if you have a high amplitude pulse infrequently applied, you may be able to make a reasonable estimate for what happens to the base load, but the pulse is little more than a guess!

 
And have you ever looked at a cell data sheet where a value for peak current is given in the text, but the charts stop a long way short of showing what actual performance you can expect? These things are often wrapped up in caveats in the small print, involving asking for the manufacturer to evaluate your application on an individual basis. You can be sure that all sorts of detail about how the product will be used will be required such as detailed load definition and environmental temperature profile before any sort of prediction is made. Even then the information the manufacturer provides will be hedged using terms such as ‘expected’ or ‘typical’ performance! And of course they will only tell you the good bits – try and get a cell manufacturer to guarantee the performance figures they give you.

 
This all indicates that the performance shown on data sheets is unlikely to be reproduced in a real world application. If you are trying to decide what cell type, from which manufacturer, you want to use in your new product then relying on data sheets alone is a risky option.

 
Even more risky is using cell data sheets to predict likely performance of a battery made up of multiple cells to give higher voltage, higher capacity batteries. Issues such as localised heating can affect performance considerably. In some cases additional features need to be included in multi cell batteries for safety reasons. When these should be implemented and how they affect to overall battery performance are critical issues. There are so many potential combinations it would not be practical to include these on data sheets, expert advice is a must. Once you have chosen your battery supplier they will of course make sure the product they provide is safe. But if you have done your initial development work based on what you think the voltage output would be, only to find that you need a couple of diodes in the battery, there is a nasty performance shortfall on its way.

 
Experience is key in understanding how data sheet information relates to likely real world performance. Using an expert early in your new product design process to select what cell type, and in what configuration will give the best performance based on a realistic assessment of manufacturers data will help reduce you project risks. If this article has got you thinking, please contact me using the enquiries form on the contacts page of this website. I am always happy to give a no obligation chat through the issues of battery selection and use

Battery Requirements Capture

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 enquiries@dmpowersolutions.co.uk or use the contact form on the website.

 

Do You Really Need Hi-Tech Batteries?

Is a Hi-Tech battery right for you?
An area that I think is often overlooked is the detailed selection of the battery to power equipment, or more precisely, the chemistry of the battery. There is the understandable pressure to select a battery that has an image in keeping with the hi-tech nature of the equipment it is intended to power. This tends to lure designers into selecting a lithium battery because of the draw and aura of having a battery perceived as hi-tech, no doubt with a little persuasion from a marketing angle too!

Making the right battery choice
Is the tendency to specify a lithium battery founded on good judgement and fact? As with most things there are pros and cons with whatever approach is taken. Sometimes the choice may not even rest with the battery performance alone, weight volume and even ease of transport are examples of factors that need to be considered. Additionally, variations in the way different battery types respond to increased loads and the operating temperature will mean that a battery that seems ideal at one end of the performance envelope is woefully inadequate at the other.

Key Parameters Check
As a quick comparison I have looked at three different primary (non-rechargeable) battery chemistries across a range of parameters, comparisons based on the same cell size.
Cell Type A
Highest energy cell
Best Operating Temperature Range
Poor rate capability (typically a few 10’s of mA, low 100’s under favourable conditions)
Start up delay needs managing in certain applications
Cell Type B
Highest Power Density
Good operating temperature range
High discharge currents (Amps) maintained down to -30°C
Minimal start up delay
High cost
Cell Type C – Low tech option
Significantly lower cost (around 20% of Type A)
No Transportation Issues
No ‘start up’ delay
Good rate capability (100’s of mA)
Low energy density
Not much performance below -5°C

Even from this relatively short comparison it can be seen that if weight and volume are not a problem, but cost and transportation are, the ‘low tech’ route really is worth considering.

Taking the correct guidance
Of course in a short blog like this it would be difficult to examine all the performance levels and present them clearly. Each new design will have its own key drivers which may push the battery selection in a different direction. That is why it is vitally important to capture all the requirements that the battery will need to meet in your design, prioritise these, and then match different battery types to them. Calling on the expertise offered by an independent expert who can examine options from a wide variety of sources, can ultimately save you time and money in your new development process.