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LIGHTS OF THE CHARGE BRIGADE
INTRO
It doesn’t matter how many fancy features
your phone has, it’s only as reliable as its battery. Rick Maybury looks at some
ways of keeping your power pack in prime condition
COPY
Every time you put your cellphone on charge
you damage the battery! The nickel cadmium cells used in most phone battery
packs should be able to withstand more than 1,000 complete charge/discharge
cycles, before there’s any significant reduction in capacity. That’s around
three to four years of daily use. In reality most people will be lucky to get more
than eighteen months of useful life out of their phone batteries; some start to
fade away in as little as six months.
So what’s going on? The main problem is fast-charging.
Nicad cells give their best when treated gently, charged slowly at the
so-called C/10 rate, which takes around 14 hours. Clearly that’s not very
convenient for a cellphone in daily use. We want to be able to re-charge our
batteries in an hour or two, consequently manufacturers supply fast chargers
with their phones. Most conventional fast chargers use a technique called negative
Delta/V, to determine when a battery has reached a full charge. Basically this
involves detecting a small drop in voltage and rise in temperature. This occurs
when the battery goes into an over-charge state. Every time this happens an
irreversible chemical reaction takes place inside the cells, slightly reducing
their ability to hold a charge. Over time it can reduce a nicad battery’s
useful life by 50% or more.
There’s more. Repeated top-ups, where the
battery is recharged before it has properly run down, encourages the so-called
memory effect. Eventually the cells inside the battery end up with different
states of charge. The charger doesn’t know this, it’s just looking for a tell-tale
change in voltage dip, that indicates one or more cells are fully charged, so
it switches off, and the rest of the cells end up being only partially charged.
This shows up as progressively shorter running times. Now for a bit of good
news; nickel metal hydride and lithium ion re-chargeable batteries do not
suffer from the memory effect, at least not to the same extent, and they don’t mind
top-up charges so much. The bad new is they also have a limited life expectancy,
and they tend to cost more than nicads; significantly so in the case of lithium
ion packs, (which also need special chargers).
Fortunately the nicad memory effect can often
be eradicated, which brings us to the subject of this month’s accessory review.
We’ve gathered together a selection of desktop chargers, that in one way or
another, can help to maintain your cellphone’s nicad battery, either by slow
and careful charging, or they have a conditioner/discharger circuit, that can
help to eliminate the memory effect. We gave each of the them a thorough
work-out, paying particular attention to charging current and minimum discharge
voltage. We’re please to say the results were reasonably encouraging. The electrical
tests were within recommended limits, cut-offs and safety features operated satisfactorily.
The only real problems concerned two mains
power adaptors, that were both dead as door-nails. They were clearly sourced
from the same Taiwanese factory, (though supplied with different makes of
charger). For the tests we substituted a third power supply (another one of the
same type). Our advice, if you’re buying from a shop, is to have the power
supply checked. If our experiences are anything to go by there could be a reliability
problem with this particular type of adaptor. They’re easily identifiable with
a large ‘Made In Taiwan’ Sticker on the back, bearing the code-number UJ-131000B
or UJ-131100BS.
REVIEWS
BTG DESKTOP TRICKLE CHARGER £30
BTG (a recent merger between Banner and
Twinchoice) have the only single-mode trickle charger in this roundup. It’s slow,
rated at just 70 mA, so reckon on a charge time of eight to twelve hours for a
standard pack, but you can almost hear the battery breathing a sigh of relief. It’s
very basic, there’s only a simple LED power indicator, and no automatic cut-off,
so remember not to leave it stewing for too long. It doesn’t come with any
instructions, though it’s reasonably self-explanatory, with little to go wrong.
Make/model BTG Desktop Trickle Charger
Typical price £30
To fit most popular makes and models
Indicators LED charge indicator
Charge current 70mA
Features reverse polarity and short-circuit
protection
Power source plug in mains adaptor
Performance ****
Ease of use ****
Build quality ****
Value for money ****
WC RATING 85%
BTG TWINCHARGER/DISCHARGER £40
Designed to simultaneously charge a phone
with battery, and second battery pack, this sophisticated design has a number
of useful features. They include fast and slow charging using a combination of
Delta V and timer control charge sensing, it has a simple test facility,
audible alarm and a discharger and the outfit includes a car cord. The unit
performed well, though we did have a little trouble getting it to work as the
mains power module supplied with our sample was completely dead.
Make/model BTG Twincharger/Discharger
Typical price £40
To fit most popular makes and models
Indicators LED charge/status and discharge, audible
warnings
Charge current 400mA (phone & battery), 600mA (battery only)
Features microprocessor controlled, timer
controlled
Power source plug-in mains adaptor, car power
cord
Performance ****
Ease of use ****
Build quality ***
Value for money *****
WC RATING 90%
(assuming a working mains adaptor...)
GRM ULTRA TWIN CHARGER £40
This is a well-specified twin-slot charger,
with a space at the front for the phone and battery, and a second slot for a
battery only. Charge currents are lower for the phone and battery together, for
safety reasons only the battery slot has a discharge function. We’re not very
impressed with the indicator labelling or instructions; what on earth are A.F,P,D,F
and B supposed to mean? The answer is printed on one of the flaps of the
cardboard packaging. The instructions, such as they are, consist of a few lines
on the back of the box, so don’t throw it away! The mains adaptor supplied with
our sample was a dud. The tests were carried out using an identically rated
power module from Hama, and it works well, but the manufacturers really should
do something about the labelling and instructions.
Make/model GRM Ultra Twin Charger
Typical price £40
To fit most
popular makes and models
Indicators charge condition, status, power and discharge
Charge current 450mA (both slots), 800mA (rear slot only)
Features discharge function, microprocessor
controlled
Power source mains adaptor and car power cord
Performance ****
Ease of use **
Build quality ****
Value for money ****
WC RATING 85%
HAMA 41060 IC HANDY CHARGER £85
This one’s an old friend. We first saw it
last year, and it’s still going strong. It’s a clever design, that can be used
to charge a range of re-chargeable batteries, by using an interchangeable
adaptor plate. It automatically senses battery voltage and type, and adjusts
its charging circuits accordingly. The state of charge is shown on a small LCD
indicator. It works well but it is a tad expensive. It might be worth
considering if you have a range of battery powered devices (camcorders, other
makes of phone etc.), but be warned that extra adaptor plates cost around £15
each.
Make/model Hama IC Handy Charger
Typical price £86 (includes
adaptor plate)
To fit most
popular makes and models
Indicators LCD capacity meter, LEDs for power,
charge, status and discharge
Charge current 500 to 800mA
Features automatic voltage selection, audible
alarm, discharger
Power source mains adaptor and car power cord
Performance *****
Ease of use ****
Build quality ****
Value for money ***
WC RATING 75%
HAMA 36401 PR-OFFICE CHARGER £100
At last, someone has put a little effort into
the design and styling of a desktop charger. Unfortunately it’s reflected in
the price, which is somewhat steep; £100
seems rather a lot to ask for a dual slot charger, with a fairly routine specification.
To be fair the LCD display panel is quite smart, with lots if useful information,
including a simple capacity meter. It’s easy to use, it works well, and it is
very eye-catching, but that hefty price tag is a problem.
Make/model Hama Pro-Office Charger
Typical price £100
To fit most popular makes and models
Indicators multi-function LCD panel, charge
mode/status, audio warning,
Charge current 400mA front phone socket, 800mA rear battery-only socket
Features discharger, LCD display, audible
warning
Power source plug-in mains adaptor
Performance ****
Ease of use ****
Build quality ****
Value for money **
WC RATING 70%
ORA FAST CHARGER PLUS £40
This is a battery-only
fast-charger/discharger. In fact it’s only moderately quick, a typical full
charge from flat, for a standard pack, takes between 2 - 3 hours, so it’s not quite
as ‘brutal’ as some of the others we’ve seen. Operation is very
straightforward, though it’s the only charger to ‘whine’. The high-pitched
whistle emitted by our sample became quite irritating. Nevertheless, everything
else checked out, and it has a good pedigree. Worth considering.
Make/model Ora Fast Charger Plus
Typical price £40
To fit most
popular makes and models
Indicators charge status and discharge
Charge current 400mA
Features discharge
Power source plug-in mains adaptor
Performance ****
Ease of use *****
Build quality ****
Value for money ****
WC RATING 82%
CONTACTS
BTG plc telephone (01992) 825825
GRM Ltd., telephone (01253) 773177
Hama UK, telephone (01256) 708110
ORA Electronics Ltd., telephone (01296)
415445
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Ó R. Maybury 1996 1209
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