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Editorial.
Welcome
to issue 18.
Well it
has been many many months since our last issue and I hope the
articles we
have
published in the past have proved useful to you. Based upon the
total absence
of
questions or comments since our last release, your existing
installations are
obviously working well
enough.
None of
us should ever be complacent where batteries are concerned and in
this issue,
I will
be discussing a problem which many of you will hopefully never
experience,
exploding laptop
batteries!
Enjoy the article and hope
you will continue to subscribe to our
publication.
Happy
Reading!
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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 Eighteen years and
has designed
charging equipment and battery monitors for some of the world
largest companies.
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ARTICLE: Battery Problems. Author:
Alan Fidler.
Over the
last 12 months or so, we have read reports of people who have
suffered a
catastrophic failure of their laptop caused by exploding
batteries. This raises concerns
about
the safety of the latest cell packs and it would be sensible to
understand
why it
happens so we can try to avoid problems
ourselves.
All of
the reports I have read focus on one type of battery, specifically
Lithium Ion
which
are rapidly replacing the older NiCad and NiMh cells which were so
popular just
a few
years ago.
There
were good reasons behind the changes in laptop power batteries, more
power,
less
weight and no memory effect were all positive reasons to switch to
lithium ion.
Unfortunately, many contain Cobalt Oxide which can in certain
circumstances go
into a
condition known as thermal runaway. This condition can be described
as a
substance or device which gets hot which results in
increased conduction or burning
which
results in more heat and so on and so forth until failure
occurs.
Explosive conditions are quite rare thankfully but they do
happen and when they go,
the
results is lots of smoke and possibly fire too. So why does it
happen and what can
we do to
avoid it?
Firstly,
it is imperative to avoid short circuiting the battery. This will
result in a large
uncontrolled current flow through the battery which will
generate a lot of heat. Never
short
out the battery terminals either directly or
indirectly.
Secondly, do not over charge the cells.
Again, heat will be the result and you could
push the
battery into thermal runaway quite easily.
Thirdly,
and this may sound obvious, do not expose the laptop and
battery to direct or
indirect sunlight or heat from any
artificial source. Keeping the battery cool at all
times
is the
key to avoiding problems.
Whilst
we are on the subject of heat, please remember that vehicles can get
quite warm,
particularly when left in full sunshine for most of the day.
You really cannot afford to
leave
your laptop anywhere in your car, including the
boot.
Fourth,
replace the battery at the end of its serviceable life.
If you
follow these simple guidelines, you should be able to avoid any
problems with
your
lithium ion cells. They are certainly very good batteries and as
long as they are
treated
with respect, will give many years of reliable
service.
Remember: Look after your batteries and
your batteries will look after you!
______________________________________________________________________
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CLASSIFIED ADS:
NEW:
AUTOMATIC NICAD CONDITIONER
Our
latest NiCad charger automatically conditions NiCad batteries by
discharging the
cells to a specified potential before
applying a 3 stage charging cycle to
recharge
the
cells safely and completely.
Features:
Automatic discharge as required before
charging cycle commences!
3 stage
charging, Constant Current (Boost) Float Charge and Trickle
charge!
Led
indications for Battery Connected, Discharging, Charging and Battery
Charged!
Available with 110/120 or 220/230 Mains
input!
RFI
Suppression!
Designed for fixed recharge
applications!
Ideal
for Switch Tripping applications!
Can be used to recharge Lithium Ion
Cells!
Go to http://www.cbcdesign.co.uk/
and click the "New Products!"
link for more information.
______________________________________________________________________
______________________________________________________________________
CLASSIFIED
ADS:
12 & 24V DC
DIMMER SWITCHES in 60W, 150W & 300W
*Adjust 12 or 24V lamps from a dim
glow to bright light with a CBC Dimmer
Assembly*
*Extends bulb life and reduces battery
power consumption*
*Works just like the dimmers in your
house*
*Easy to install with integral
connections*
*20 year industrial design
life*
________________________________________________________________________
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READERS QUESTIONS.
Questions from in-house
1.
What is the optimum charging voltage for Nicad or NiMH
Cells?
1.41 Volts Per Cell.
2. What is the preferred charging regime for
the same cells?
Constant current terminated by time,
voltage drop sensing or voltage
peak.
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SUBSCRIBER ADS.
These ads
are published by our subscribers. DC Supply & CBC Design is not
responsible
for the content of the websites
accessed via the links printed
below. Access these sites
at
your own
risk!
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______________________________________________________________________
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