What Cellphone

 BootLog.co.uk

HOME   SOFTWARE   TOP TIPS   ARCHIVE   GLOSSARY   OTHER STUFF

LIGHTS OF THE CHARGE BRIGADE

 

INTRO

It doesnít matter how many fancy features your phone has, itís 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 thereís any significant reduction in capacity. Thatís 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 whatís 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 thatís 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 batteryís useful life by 50% or more.

 

Thereís 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 doesnít know this, itís 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 donít 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 monthís accessory review. Weíve gathered together a selection of desktop chargers, that in one way or another, can help to maintain your cellphoneís 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. Weíre 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 youíre 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. Theyíre easily identifiable with a large ĎMade In Taiwaní 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. Itís 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. Itís very basic, thereís only a simple LED power indicator, and no automatic cut-off, so remember not to leave it stewing for too long. It doesnít come with any instructions, though itís 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. Weíre 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 donít 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 oneís an old friend. We first saw it last year, and itís still going strong. Itís 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 itís 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. Itís 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 itís only moderately quick, a typical full charge from flat, for a standard pack, takes between 2 - 3 hours, so itís not quite as Ďbrutalí as some of the others weíve seen. Operation is very straightforward, though itís the only charger to Ďwhineí. 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

 

---end---

R. Maybury 1996 1209

 


 

[Home][Software][Archive][Top Tips][Glossary][Other Stuff]


Copyright (c) 2006 Rick Maybury Ltd.

admin@rickmaybury.com