DC Supply! Monthly Electrical Ezine

CBC Design (tm) - August 2001 Issue. ISSN 1475-3464
Email: cbc_design@btconnect.com

"...Maintaining a reliable DC supply."



- Introduction
- How to maintain your batteries. (Article)
- Ripple free supplies (Article)
- Competition - Win a FREE battery tester!.
- Readers Questions



Welcome to the August issue of "DC supply".
Batteries play an important role in the modern high-tech world in which we live. Just think about the appliances and equipment in your own home that run on batteries and you will begin to see just how important they are. Everything from small household appliances and automobiles to large ocean going vessels all depend upon a smooth DC supply.

If you own a lap-top computer, a mobile home, boat or barge, electric vehicle or any household appliance that uses batteries as a primary power source, this ezine is sure to interest you. If your kids own toys that run on batteries, we can show you how to reduce your costs.

Each month we'll look at the latest developments in battery technology, DC power supplies, battery maintenance and how you can save money as a result. Learn how to recondition your laptop batteries so you can use your computer, self powered, like you did when it was new.

We'll be producing seasonal care guides for boat owners, campervan and camping enthusiasts, divers & laptop computer owners. Concise information on just how you can make sure your batteries continue to work, even on those cold winter mornings!.

Are you tired of paying electricity bills?. We can show you how to generate your own DC & AC supplies from solar and wind power generators for marine and domestic applications.

Over the coming months, the articles in this publication can be printed, saved and used as a valuable reference that you can refer too time after time, after all, batteries are expensive!. Why throw money away buying new ones when all that your old batteries need are a bit of TLC (tender loving care).

We hope you find our content interesting and welcome any comments, questions, suggestions or relevant articles you may have.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Editor: Alan Fidler.

Alan is the owner and manager of CBC Design, a leading battery management company based in the UK. He has worked in the industry for over seventeen years and has designed charging equipment and battery monitors for some of the world largest companies.

ARTICLE: How to maintain your batteries!. Author: Alan Fidler.

Batteries are probably one of the most mis-understood power sources available today. Fit them and forget them seems to be the most common philosophy but does this lead to premature failure?.

Sadly, YES!. Often a total lack of maintenance leads to a gradual reduction in performance which eventually leads to an unreliable DC supply just when you need it most.

Those of us with lap-top computers are all too familiar with the above scenario but by following a few simple guidelines, much can be done to prevent batteries failing before they should. With the right care, batteries can last for years at a time and in some cases, an entire decade.


Often the lack of maintenance is due to limited knowledge rather than a reluctance to give them the attention they need and deserve. If you look after your batteries, your batteries will look after you.

Like most of us, batteries need to be exercised in order to perform to the best of their ability. By following the guidelines below, you should be able to reduce your consumption of new batteries, increase the performance of your existing ones and save money as a result.


Nicad batteries (Nickel Cadmium) are widely used in most household appliances including Laptop Computers, calculators, personal organisers, electric toothbrushes etc.

Nicad batteries must be charged and discharged correctly in order to obtain the best possible performance from them. If your Nicad are not lasting as long as they should, you need to change the way in which you use them.

Cycling the batteries will result in a considerable improvement. Simply put, cycling involves discharging the battery COMPLETELY, then recharging it. Maintain the battery by using this regime at least once per week.

Use your battery until it's flat and only then use an external DC supply should you wish to continue using the appliance. All too often, laptop computer owners for example, use an external DC supply rather than the battery. Unfortunately, Nicad batteries have a characteristic called memory. The battery remembers how much it is used and becomes incapable of working for longer periods as a result. Cycling the battery compensates for this phenomenon.

We will be looking at Nicad batteries in more detail next month!.


NiMH batteries (Nickel Metal Hydride) are similar to Nicad's but without the inherent memory effect. Maintenance is simply a matter of recharging the cells at the correct current level for a fixed period of time.

NiMH cells can be recharged following a partial discharge however its difficult to judge how much current needs to be replenished so overcharging the battery is a possibility.

To get the best performance over time, it is safer to discharge the battery completely between recharge cycles. This will help to extend the life of the battery, which is important since the number of cycles is fixed to between a few hundred and 1000 cycles in most cases depending upon the manufacturer.

We will be comparing NiMH cells to Nicad in more detail in next months issue!.


Lead-acid traction batteries are designed to deliver large discharge current for short periods of time. Your automobile battery is a typical example of a traction battery. They are also used in trucks, boats, forklift and platform lifts to name but a few applications.

Many of today's traction batteries are maintenance free which means there is not much that needs to be done to look after them properly.

As long as the charging alternator or generator is functioning correctly and the terminals are protected from corrosion, the battery should perform as per the manufacturers spec for its full service life.

Wet lead-acid batteries may need to be topped up using distilled or de-mineralised water. The liquid inside the battery known as the electrolyte is normally maintained at 1cm above the lead plates although this can vary so check with the battery manufacturer.


Leisure batteries are used in applications where a gradual discharge occurs. Typical examples would include caravan or campervan supplies for lights, TV's etc.

Unlike traction batteries, they need to be cycled on a regular basis and recharged using a battery management charging system or well regulated alternators to get the best performance characteristics. There may be ripple implications too so make sure your charger is smoothed if necessary. See our article on ripple for an explanation.

Nowadays, leisure batteries are all maintenance free and topping up is not required. Maintenance is limited to applying an anti corrosive substance to the battery terminals.


To get the best performance and the longest life from any battery depends upon how well it is maintained. By following the guidelines above, it is perfectly feasible to extend the life of a battery by months and in some cases years.

"Look after your batteries and your batteries will look after you!"



Do you use non-standard batteries that are difficult to obtain through retail outlets?

CBC Design can supply a wide range of special application cells for everything from camcorders & laptop computers to calculators, watches and dive computers.

Go to http://www.cbcdesign.co.uk/chargers/order.html and complete the details including the type of battery you require.


ARTICLE: Ripple Free Supplies: Author: Alan Fidler.

Ripple is AC superimposed on a DC supply. In simplistic terms, ripple can be thought of as a variation of the dc voltage in a positive and negative direction around the actual DC voltage required. A 12V DC supply with 1% of ripple would vary from 11.88VDC to 12.12VDC a number of times per second (Hertz) depending upon the frequency of the incoming mains source to the power supply.

Batteries are pure DC sources so ripple is not present. DC Power supplies which are powered from 110 or 230V AC supplies will have a certain amount of ripple which is related to the amount of filtering fitted to the supplies output stage. The ripple is normally at the same frequency as the mains supply, 50 or 60HZ unless the supplies use switch-mode technology. We will be looking at switch-mode in more detail next issue!

The ability to withstand ripple varies from one type of battery to another and indeed from one type of appliance to another too.

Inexpensive automobiles chargers are rarely smoothed and can have a ripple factor as high as 20%. Whilst your automobiles battery is designed to withstand, ripple, leisure batteries are less tolerant.

In extreme cases, excessive ripple can actually cause overheating of the battery which causes the lead plates to buckle thus reducing the performance of the battery. The components inside your equipment can suffer in a similar manner.

Make sure your power supply has a ripple factor that does not exceed the ratings of your battery and equipment. You can check for ripple on your power supplies by connecting an oscilloscope (set to "AC") to the DC output or use a digital multimeter set to "AC" to get an average figure.

If you are purchasing new power supplies or charging equipment, make sure it meets your requirements by asking the manufacturer to specify the output ripple for you. If they are unable too, you should consider using a different supplier.



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Subscribe to our ezine and you will be automatically entered into our competition where you can win a FREE battery tester for your automobile, campervan or boat.

Simply send your email address (No free email) to cbc_design@btconnect.com with the words "SUBSCRIBE" in the subject line.



Questions from Kevin Spinks! What does ampere hour mean?

Ampere hour is an expression of the battery rating. A 10AH battery can deliver ten amps for 1 hour or 1 amp for ten hours, hence the 10 ampere hour rating.

Question2! What are milliamps?

A milliamp is one amp divided by 1000. A 100mA battery is therefore a 0.1A battery.



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