DC Supply! Monthly Electrical Ezine

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

"...Maintaining a reliable DC supply."



- Editorial
- DC Can be Dangerous. (Article)
- Over wintering your Batteries(Article)
- Competition - Win FREE battery pack!.
- Readers Questions



Welcome to this months issue of "DC supply".
We were all appalled at the terrorist attacks on New York and Washington last month
and DC Supply would like to offer heartfelt sympathy to everyone effected by the
horrific events that took place. It is difficult to comprehend how individuals could have
such a lack of respect for the lives of so many innocent people. Unbelievable!
This month we are going to look at safety and maintenance issues.
Our article entitled "DC can be Dangerous" looks at an incident that took place
in the UK where an apparently safe 12v battery installation resulted in a rather
nasty accident. There is definitely a lesson for us all here.
The fall has arrived. Leaves are dropping and temperatures are dipping into single
figures on a regular basis. Like it or not, winter is just around the corner.
Now is a good time to prep up your cells for the cold months ahead.
Our seconds article looks at how to over wintering your batteries and
maintain cell performance during the cold spells. 
Last months competition was won by Helen Dukesbury in Bristol. Congratulation
Helen. With "AA" batteries being one of the most popular cells available, we
are repeating the competition again this month so good luck to you all!
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 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: DC can be Dangerous!. Author: Alan Fidler.

In last months Readers Questions, I was asked if batteries were dangerous.
At low potentials such as 12 and 24 volts, they are reasonably safe of course but still
have the potential to harm the end user.
The following account is true story and demonstrates just how easily a low voltage
battery can cause a great deal of pain and discomfort if abused.
Many years ago, when I was employed as a test engineer for a local UK charger
manufacturer, I witnessed a rather horrific accident. Nobody died but the result
was never the less painful and not something I would like to have suffered.
A colleague was connecting charging cables to a 12V lead-acid battery fitted inside
an enclosure. He was using a metal spanner/wrench to tighten the connections but
what he did not realise was that it was in direct contact with the wedding ring he
wore on his right hand.
His mind was not on the job and he accidentally allowed the wedding ring to come
into direct contact with the negative terminal of the battery just as he applied the
spanner to the positive terminal. The result was a dead short!
Almost immediately, a colossal amount of current flowed from one terminal of the
battery to the other through the wedding ring which was by now getting hotter
and hotter. Since the amount of conductive material in the ring was quite small,
it reached a temperature of over 85oC almost instantly and began burning its
way through my colleagues finger.
We were able to break the supply quickly but the damage was already done.
The ring caused serious burns and to make matters worse, swelling was
beginning to occur around the ring making it more and more uncomfortable.
Incidentally, we estimated that over 190 amps flowed through the ring and
Where batteries are concerned, none of us can ever afford to be to complacent.
Even a low voltage pack with no ability to deliver an electric shock as such can
still be very dangerous in the wrong hands.
Here is a quick list of do's and don' t's which will help keep you and your
batteries in good order:
1. Remove wedding rings and loose jewellery from your person when handling
batteries. This includes bracelets, necklaces and similar items.
2. Keep naked flames, cigars and cigarettes or any spark or heat source
well away from from batteries. Lead acid cells produce hydrogen gas which
is highly explosive.
3. NEVER allow the battery to become short circuit. This is VERY dangerous.
4. Do not connect or disconnect live appliances to a fully charged battery. The
resulting sparks could cause an explosion.
5. Always wear safety goggles or glasses when topping up wet lead-acid or
Nicad batteries.
6. Allow plenty of ventilation around batteries on charge. Never recharge a
battery inside a sealed enclosure unless directed by the battery manufacturer.
7. Never parallel batteries (+ to + and - to -) of different capacities.
8. Stay focused on what you are doing at ALL times.


*** NEW! 12 and 24V DC 60 Watt lamp dimmers ***

Dims single or multiple lamp assemblies with a maximum rating of 60 watts!
Lamps can be adjusted from a dim glow to bright light!
Regular use reduces battery power consumption and increase lamp life!

Go to http://www.cbcdesign.co.uk/chargers/dimmer.html and take a look at the
product in more detail NOW!.


ARTICLE: Over wintering your batteries: Author: Alan Fidler. 

With the fall upon us, winter is almost upon us so now is the time to look at
your batteries with a view to winter storage and maintenance.
Where cells are installed in automobiles or appliances that won't be used
at least once per month, they should be removed and stored in a cool dry
location, preferably in an ambient temperature of at least 15oC or so.
Clean the battery terminals and remove all traces of corrosion that may have
built up during the summer. Apply a liberal quantity of anti-corrosive jelly
to each terminal, making sure that the lead contacts are completely covered.
Wet lead acid cells may need to be topped up as per the manufacturers
instructions using distilled or de-mineralised water. NEVER use tap or
rain water since they contain impurities that lower the internal resistance
of the battery. Many people do not realise that in it's purest form, water is
an insulator.
The battery should be recharged at least once per month using a voltage
controlled charging system. A quality battery management charging system
automatically reduces the output from  a bulk mode to a trickle charge as
the battery charges. Chargers of this nature can be left permanently connected.
Inexpensive transformer/rectifier based chargers can be used to recharge
your cells on a month by month basis but you must make sure that the
battery is not over charged. In fact, it is now possible to convert the cheap
and cheerful charger into an automatic voltage controlled system by fitting
a suitable charge controller between the charger output and battery.
Permanently installed batteries should be recharged at least once per month
using a suitable external charger or on board alternator. The battery should
be recharged until the voltage reaches 2.3 volts per cell, about 13.8VDC on
a 12 volt installation. Using an on board alternator, the output current will
gradually drop as the battery voltage rises and once the charging current
is approx equal to the battery capacity divided by 600, the battery is charged.
If you have any doubts about the performance of your batteries, they can be
tested. For a traction battery, connect a load that simulates the discharge
current drawn during an engine crank. Your battery manufacturer will be able
to tell you how long to leave the load connected for and what the minimum
battery voltage should be at a given temperature during and after the test.
Leisure batteries can be tested in a similar manner. You simply apply a load
with a rating of 1/10th of the battery capacity and record the time taken to
discharge the battery to 1.75 volts per cell. If the battery performs as per the
manufacturers specification they can be returned to service.
In either case, if your batteries do not pass the discharge tests, replace them
as soon as possible. In many applications the batteries are an essential part
of the system and should be treated accordingly.
Look after your batteries and your batteries will look after you!.


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Questions from Andrew Shaw! What does OEM mean?

OEM stands for Original Equipment Manufacturer. It is a term reserved for companies
or individual who manufacture unique products. 

Question2! What is a Bespoke Product?

A Bespoke product is custom made to suit an individual application or client



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