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EDITORIAL. 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!
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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
spanner.
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.
______________________________________________________________________
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______________________________________________________________________ ______________________________________________________________________ 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.
TESTING YOUR BATTERIES
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!.
______________________________________________________________________ ______________________________________________________________________ CLASSIFIED ADS: YOUR url ON over 600,000 sites FREE! For a limited period, you can get your website submitted FREE to over 600,000 search engines, directories and classified ad sites. Email your url to enquiries@searchenginesubmituk.com with the words "FREE SUBMISSION" in the subject line. Free OPTIMISATION included!. http://www.searchenginesubmituk.com ______________________________________________________________________ COMPETITION: Subscribe to our ezine and you will be automatically entered into our competition where you can win a FREE Nicad "AA" battery pack. Simply send your email address (No free email) to cbc_design@btconnect.com with the words "SUBSCRIBE" in the subject line. ______________________________________________________________________ READERS QUESTIONS. 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 requirement. ______________________________________________________________________ UNSUBSCRIBE. This ezine is sent to companies or individuals who have chosen to subscribe to "DC Supply". If you wish to unsubscribe, send an email with the words "UNSUBSCRIBE" in the subject line and we will cancel your subscription. ______________________________________________________________________ "You may distribute this ezine to whomever you wish as long as it is sent in its entirety." (c) copyright 2001 CBC Design. Subscribe TODAY! by sending an email with "SUBSCRIBE" in the subject line. |