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BATTERY CARE
HEAD
ASSAULT ON BATTERIES
INTRO
The battery is the hardest-working component
in your cellphone. They’re subjected to
continual abuse and lead short, miserable lives, but it doesn’t have to be like
that...
COPY
Did you wait for the low battery warning on
your phone to flash, before you put it on charge? Probably not, we’re all
guilty, but by continually re-charging a battery before it has properly
discharged, its life will almost certainly be shortened.
Nickel cadmium (nicad), and to a lesser
extent, nickel metal-hydride battery packs do not respond well to repeated
top-up charges, after a while they become accustomed to shallow
charge-discharge cycles and eventually their capacity will be reduced. That’s
only part of the problem, though. The fast-chargers supplied with most phones
actually shorten the lives of the cells inside the battery by over-charging
them slightly each time. The combined effects of this treatment typically
result in a halving of life expectancy, from a potential of 1,000 or more
cycles, to 500 or less, depending how often the phone is used. A battery that
might otherwise have lasted a couple of years may need replacing after just a
few months.
It doesn’t have to be like that, the first
thing to do is to avoid top-up charging. Leave the phone switched on when you
come home, and don’t put it on the charger until the battery warning comes on
or the phone switches itself off, that will go some way to help prevent
cell-imbalance, which gives rise to the so-called memory effect.
Cell imbalance or ‘memory’ occurs when the
cells inside the battery reach varying states of charge. Most fast chargers
work by sensing a small drop in voltage and a rise in temperature in the pack,
but this can happen when only one cell has reached full charge, leaving the
others with a partial charge, and hence a reduced capacity for the pack as a
whole.
However, careful charging won’t help
batteries that have already developed a memory, but there’s something you can
do about that as well. Cell imbalance can be eliminated by discharging all of
the cells in the pack, so that they’re on an equal footing the next time
they’re charged. In practice it can take several complete charge/discharge
cycles to completely restore the pack’s capacity, and even then it may never
fully recover, due to the damaging effects of fast charging, but if the battery
is still relatively new, regular discharging or ‘conditioning’ can
significantly extend a battery’s useful life.
Discharging is not simply a question of
draining the battery, moreover the contacts should never be short-circuited.
This will almost certain blow an internal fuse, or rupture the cells; in
extreme cases this could result in an explosive release of super-hot gasses,
and you would not like that! Nicad and NiMh cells must never be discharged to
less than 1 volt per cell, doing so risks a condition known as deep-discharge
or reverse polarity, which effectively destroys the cells.
That brings us to the subject of this months
accessory review. We’ve been looking at a selection of chargers, that have
built-in dischargers or conditioners. They have specially designed restive
loads that give a controlled discharge, with a safety cut-out, that protects
the cells from over-discharge.
To assess how well they work we’ve tried them
with a selection of batteries of known performance, both new and old, and
checked their capacities before and after each charge/discharge cycle using the
same procedures we developed for our standard battery tests. We also measured
the charge and discharge currents, and cut-off voltages, to ensure they
wouldn’t cause any damage to the batteries they’re used with. For the record
all the units were satisfactory, though one or two of them were quite close to
what we would consider to be the minimum safe cut-off voltage.
In general it’s inadvisable to discharge NiMh
batteries, they can develop cell imbalance but they have a higher
self-discharge rate than nicads and the charge will eventually drain away. If
you have a NiMh pack that has developed a memory put it to one side for two or
three weeks, and try again, it might well recover on its own. All of the
chargers we’ve tested say they can be used safely with both types of battery,
though none of them mention that NiMh packs have different charge
characteristics, and may not achieved full charge when the charging cycle is
completed. We have found that in most cases full charge is reached by removing
the battery for a couple of minutes, and replacing it on the charger.
For once we’ve managed to pin-down
manufacturers and suppliers to recommended or suggested retail prices, though
be warned they’re for guidance only and the street prices may be appreciably
lower. By the way, cell phone accessory dealers always leave off the VAT, the
prices we’ve shown are VAT inclusive.
ALLGON ALL-CHARGER
Unusual desk-top or wall-mount design with
flip out stand on the back. All-Charger can accommodate both the phone and a
spare battery, at the same time. The instructions are not very clear on this
point but it only discharges the battery pack, and not the battery which is on
the phone. The phone was a tight fit on our sample, we later discovered the
contact plate had worked loose, but it was a simple matter to click it back
into place. Charging starts automatically when the phone or battery is
inserted, discharge mode has to be manually selected. The indicator for the
solo battery back charger is a bit confusing, it changes to yellow whilst
discharging, and green when fully charged, but there’s not a lot of difference
between yellow and green. Discharge current is below 300mA, which gives a
discharge time of around 3-hours on a 1AH pack. Charge performance is good, all
batteries were restored to full capacity. Worth considering.
Make/model Allgon
All Charger
Typical price £50
Suitable for most
makes, inc. Maxon 450, Ericsson 237/337, Motorola 5200, 7200, 8200, Flare,
International, Elite, Nokia 2010, 2110, Orange 2140
Indicators green
LED for power on, dual colour (red & yellow) LEDs for charge and discharge
Features simultaneous
charge for battery and phone, discharge on pack only
Power source plug-in
mains module
Performance ****
Ease of use ***
Build quality ***
VERDICT 80%
Contact ALLGON
ANTENNAS, Unit 11, The Courtyard Whitwick Business Park, Stenson Road,
Coalville, Leicester LE67 3JP. Telephone (01530) 510013
HAMA IC HANDY CHARGER
Neat desktop charger/discharger unit for a
single battery pack. Various types and styles of battery can be accommodated
using an interchangeable adaptor plate. The device automatically senses battery
voltage (4.8, 6 or 7.2 volts), which is displayed by one of three red LEDS.
Battery capacity is shown graphically by a small LCD panel. Charging starts
immediately, the discharge mode has to be manually selected by pressing a small
button. Discharge time is around 2.5 hours on a 1AH pack with a current of
350mA. A buzzer sounds and LED flashes
when charging is complete and unit reverts to a trickle charge condition. It
gets quite warm, so avoid leaving it on highly polished or delicate surfaces. A
little pricey though performance is good and the discharge cut-off point on our
sample was spot on the 1.0 volt safety limit.
Make/model Hama
41060
Typical price £70
Suitable for Ericsson
GH337, Motorola Micro TAC, Nokia 1011/2110, Seimens S1
Indicators LCD
capacity indicator, LEDs for power, charge, discharge and battery voltage
Features single,
multi-voltage battery charger with audible alarm
Power source plug-in
mains adaptor and car battery cord (supplied)
Performance ****
Ease of use ****
Build quality ****
VERDICT 75%
Contact HAMA
Unit 4 Cherrywood, Chineham Business Park, Basingstoke, Hants RG24 OWF.
Telephone (01256) 708110
ORA FAST CHARGER PLUS
Simple desktop charger for single battery
packs. Slot in the battery and the charging cycle begins, accompanied by a
slightly irritating high-pitched whine. When charging is complete the red LED
indicator flashes green. Discharge is manual, by pressing a small button on the
top panel. There’s no power indicator, so unless a battery has been inserted
there’s no way of knowing if the unit has been switched on or not. Charge
current is a little below average, so it’s fairly relaxed in operation, but
that’s no bad thing, a 1Ah pack takes just over 3-hours to charge from flat.
Discharge current is 300mA, giving a discharge time of around 3-hours. Good
performance with all packs fully charged. Good value, reccomended.
Make/model Ora
Fast Charger Plus
Typical price £40
Suitable for most
popular makes
Indicators dual-colour
LED for charge cycle and single colour LED for discharge
Features single
battery charger/discharger
Power source plug
in mains module
Performance ****
Ease of use *****
Build quality ****
VERDICT 85%
Contact ORA 28/29 Faraday Road, Aylesbury, Bucks HP19
3RY
Telephone (01296) 415445
ORA QUICK CHARGER CONDITIONER
Smart-looking desk-top charger for a single
battery pack. Easy to use, charging starts as soon as the pack is connected,
with the option to run through a discharge cycle. Built-in sensor automatically
checks if battery suitable for fast charging (i.e. no internal thermal cut-out)
and alerts user with warning buzzer. Plenty of good advice and warning messages
in the instructions, though they incorrectly state that it is powered from a
120 volt AC source. Charge state shown by a row of LED. Higher than average
charge current will charge a 1Ah pack in around an hour. No power-on indication
when unit is connected to the mains (but not operating). Discharge current of
just below 400mA, a little on the high side but satisfactory. Cut-off voltage
very close to 1.0 volt. Good performance, all packs fully charged. Worth
considering.
Make/model Ora
Quick Charger Conditioner
Typical price £50
Suitable for most
popular makes
Indicators LEDs
for charge level and discharge mode
Features single
battery charger/discharger
Power source plug-in
mains adaptor, car power cord (supplied)
Performance *****
Ease of use ****
Build quality ****
VERDICT 80%
Contact ORA 28/29 Faraday Road, Aylesbury, Bucks HP19
3RY
Telephone (01296) 415445
UNIROSS UNIVERSAL FAST CHARGER/DISCHARGER
Very similar to the Hama unit (some might say
identical...), though on paper at least it’s a tad cheaper and the discharge
cut-off voltage on this particular sample was very slightly higher. Similar
general comments apply though, it runs quite warm, and even though the guide
price is a little lower it is still quite pricey.
Make/model Uniross
UCC1
Typical price £64
Suitable for most
makes (with suitable adaptor plate)
Features single,
multi-voltage battery charger with audible alarm
Power source plug-in
mains adaptor and car battery cord (supplied)
Performance ****
Ease of use ****
Build quality ****
VERDICT 78%
Contact UNIROSS
Unit 4, Blackfriars Road, West End Trading Estate, Nailsea, Avon BS19 2DJ. Telephone (01275) 858101
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Ó R. Maybury 1995 1110
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