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BACK IN CHARGE...

 

INTRO

Feeling run-down, drained, no energy? What Cellphone has been testing an assortment of replacement battery packs, to perk up your phone-calls and put you back in charge

 

COPY

Who built Stonehenge, where do wire coathangers come from and why does the low-battery warning on a cellphone always start bleeping at the critical point in a conversation? They’re some of the great mysteries of our time. We don’t know the answers to the first two, but maybe we can help you avoid the third one, by suggesting that you buy a new battery for your mobile phone.

 

Even if your current phone battery lasts all day you’ll have to buy a replacement sooner or later. Re-chargeable batteries have a finite life, and depending on how the phone is used, may last for as little as six months, before they need replacing. It’s getting better though, the nickel-cadmium (NiCad) and nickel metal hydride (Ni Mh) re-chargeable batteries used on most mobile phones are improving all the time, moreover newer lithium-ion batteries, now being introduced on some models, they give longer talk times, and need replacing less often.

 

However, for a while at least most of us are stuck with nicad and NiMh batteries, and when you come to buy a new one you’ll be faced with a bewildering choice. In short the world and his wife now market cellphone batteries. They range in quality from manufacturer’s own replacements, to cheap and sometimes nasty unbranded packs that give out after only a few months. But how do you sort the wheat from the chaff? It’s not easy, you can’t easily open them up to see what sort of cells are being used, and even if you could that wouldn’t necessarily tell you much. We’ve even heard of battery packs containing low-grade Chinese cells bearing ‘Made in Japan’ labels.

 

There are other factors to consider as well, including the choice between nicad, and newer nickel metal-hydride types, which have a higher capacity, and do not suffer anything like as much from the dreaded energy-sapping memory effect.

 

NO THANKS FOR THE MEMORY....

Memory is a catch-all term used to describe a range of maladies that afflict nicads, and to a lesser extent, nickel metal-hydride batteries. The end result is the same, though, and that’s a reduction in capacity after a just a few months use. In theory a nicad battery can withstand around 1,000 charge/discharge cycles, before its capacity or ability to hold a charge begins to tail off. Most cellphone users will be lucky to get half that much, and some heavy-duty users may notice a marked reduction in running time after just a few weeks.

 

The most common cause is something called cell-imbalance. Inside a cellphone battery there’s a number of separate cells -- five in the case of most 6-volt packs -- connected together in series. In an ideal world they would be carefully matched to have same charge/discharge characteristics, in practice they vary widely. Most ‘fast’ battery chargers use a technique known as Negative Delta V, to sense charge condition. When a cell in a battery is fully charged it undergoes a small rise in temperature and a slight voltage drop. However, unless the cells are matched they will not all achieve full charge simultaneously. Over time the disparity can increase, so that maybe only two or three cells ever reach full charge, the others only get a partial charge, resulting in progressively shorter running times.

 

Fortunately this particular effect can be reversed, by taking all the cells in the pack through a series of deep charge/discharge cycles, so they’re all on an equal footing once again. Some accessory chargers and one or two chargers supplied as standard with phones have a ‘refresh’ facility that, if used regularly, can help prevent the build up of cell imbalance.

 

The other problem concerns the life-shortening effects of fast-charging itself, and these are irreversible. Ideally a nicad battery should be charged at what’s known as the C/10 rate, which typically takes around 12-14 hours, which is great for the battery, but inconvenient for mobile phone use. Fast chargers -- that take only an hour or so -- actually damage the battery every time they’re used. Delta V, which chargers use to sense when a battery is full charged, occurs when the battery has gone in to a state of overcharge, and every time that happens, however briefly, some breakdown of the battery chemistry occurs. The amount of damage is quite small, but it all adds up, and the effective lives of some heavily-used batteries can easily be halved.

 

WHICH TYPE?

Nickel metal hydride batteries are less prone to memory effects, and have a higher capacity, but they are more expensive, take longer to charge and earlier types had shorter lives, though nowadays there’s not a lot in. On the other hand there’s still plenty of life left in nicad technology; improvements are being made all the time, and they’re a lot cheaper so don’t write them off just yet.

 

You may see claims that NiMh batteries are more environmentally friendly than nicads, as they contain fewer noxious chemicals. That’s true but all re-chargeable batteries should be disposed of responsibly. Never throw them away, put them into household rubbish or incinerate them, not if you want to live a long and healthy life. Take them back from whence they came, to the dealer, or your local authority amenity tip where they can be disposed of safely, or the materials recovered and recycled.

 

BUT WHICH ONE?

Which brings us back to the key question, how do you choose? It’s mostly common-sense. The old maxim about getting what you pay for certainly holds true for cellphone batteries. You can be fairly sure that a battery pack, made by a well-known  manufacturer, brought from a reputable dealer, will perform better and last longer than one with no name on it, purchased from a stall in a street market.

 

To help you out we’ve been putting a range of cellphone batteries through some rather stringent tests, in what we believe is the first in-depth survey of this kind, and we hope it will provide a benchmark for future reports. As with all of our accessory tests we’ve focused on one particular cellphone, the ever popular Motorola Micro TAC/Classic/ Elite/digital series. We chose this phone primarily because it has a very large user-base, and as a consequence it’s supported by more accessory manufacturers, so we have a broader range of products to consider. It has a wider relevance too, and manufacturers will normally use the same cells in other styles of (similarly sized) battery packs, and apply the same sort of care and quality control during manufacture. Initially we planned to look at a wide range of capacities but in the end we elected only to include longer-lasting higher capacity batteries, in the 1 to 1.5 A/hr range, which are what most cellphone users end up buying.

 

THE TESTS

How do the tests work? We thought long and hard about this, and tried several different techniques, including the obvious one, of actually using the batteries on phones. However, apart from the time and inconvenience involved, we found this method lacked consistency. We also considered some of the commercially available battery test instruments, but none of the ones we looked at produced the sort of data we needed, that reflected typical patterns of use. In the end we decided to design and build a test rig of our own, that would give the batteries a really thorough workout.

 

The concept is simple. During a test run each fully-charged battery is subjected to two levels of discharge: level one is a continuous low current drain, representing the phone switched on, ready to receive calls; level two involves the higher current drain of making a call. Each battery goes through two test-cycles: the first represents medium to heavy usage of two five-minutes calls per hour; the second is a much more demanding routine that simulates four five-minute calls an hour. A voltage sensor circuit, set to same level as the phone, cuts in when the battery voltage falls below a pre-set limit, stopping a clock that shows precisely how long each battery pack lasted. Each routine was repeated three times, and the average time taken.

 

Nicad and nickel metal hydride batteries need to be ‘run-in’ before they reach full capacity, so each pack went through three complete charge/discharge cycles before the tests were carried out. We used a slightly different charging regime for nickel metal hydride batteries. Most chargers are designed for nicad batteries and NiMh packs can trigger their cut-off circuits too early, before they’ve reached full capacity. The trick is to remove the battery from the charger for a few minutes, then put it back on, and it will usually continue charging for a short while longer.

 

The one thing we cannot easily test at this stage is long-term life-expectancy, and that’s where you come in. If you’ve got a battery horror story then we’d like to hear about it, or maybe you’ve a battery pack that just keeps on going, we’d like to hear about that too. Hopefully we’ll repeat this survey next year, by which time we will have built up a significant database of test results and user feedback.

 

PRICES

We tried, believe us we tried to get suggested or recommended retail prices out of accessory dealers and manufacturers but as with most things cellphone there’s simply no reliable pricing structure, even if there were the price would probably change by the time this survey went to press. We’ve seen the same battery selling with a £8.00 differential in shops less than fifty yards apart, and be careful of the add-on VAT, which many dealers still insist on tacking on, even though the majority of their customers are now private users. In short that means we cannot give you meaningful value for money ratings, so you’ll have to do the shopping around.

 

PERFORMANCE

In addition to the results in the table there are some general points to be made. Most Nickel Metal Hydride batteries outperform their nicad cousins, but not by as much as you might suspect, taking into account the price differential. Where they do score, however, is their lack of memory effect and better power to weight ratio, which might be important if space is at a premium. We’ve included the weights of all the packs tested. We thought it might be important but as you can see there’s actually not a lot in it and in the end it didn’t influence the final outcome.

 

We opened up a random selection of packs, to check the contents against what was printed on the outside. (Don’t try this yourselves, most packs are ‘welded’ together, and opening them up can cause irreparable damage). In addition to the batteries there should be at least one, and preferably two safety devices in the form of a fuse or thermal cut-out. This is necessary to prevent the cells from bursting or emitting super-hot hydrogen gas, in the event of a short circuit. This can happen if, for example, you carried a spare battery in a pocket or purse, along with a bunch of keys, so be careful! All of the batteries we checked were satisfactory in this respect. At least one pack had differently rated batteries to that stated on the case, we hope this was a mistake, in any event we adjusted the results to take this into account.

 

THE BOTTOM LINE

As you can see from the table most of the packs we tried fell into the two to three star category which rates them as average to good. We’re happy to use any of them, if the price is right. Only four batteries from Andrew, Ora, Uniross and Yokohama, were awarded four stars, and that sets them apart from the crowd as being particularly good performers, especially on heavily used phones. Just one pack receives the ultimate accolade, a five-star rating, and that’s the Ora MBPH 1900B, an outstanding nickel metal-hydride pack that beat the others by a very significant margin.  

 

TABLE 1 -- THE RESULTS

Make/Model                 

Type

Cap

A/h

Weight

(grams)

Run 1

(high)

Run 2

(low)

WC

Rating

Andrew BC 115 B

Ni-Cd

1.25

160

3.54

7.50

***

Andrew BH 115 B

Ni-Mh

1.45

162

5.25

8.14

****

Chance Way ZE0102

Ni-Cd

1.0

151

4.45

5.30

**

Chance Way ZE0102MH

Ni-Mh

1.1

123

4.15

7.05

***

Fameart PB07-2B

Ni-Cd

1.2

160

4.31

7.07

**

Fameart PB07-2B*

Ni-Mh

1.5

173

4.48

6.33

**

GRM Power Wave

Ni-Cd

1.0

153

4.00

7.02

***

Hama 41015

Ni-Cd

1.2

165

3.58

7.38

***

Ora MBP1500B

Ni-Cd

1.5

160

5.02

8.58

****

Ora MBPH 1900B

Ni-Mh

1.5

175

5.45

9.29

*****

Twinchoice QB211OG3

Ni-Cd

1.1

175

4.30

7.48

***

Uniross UCB 310SBL

Ni-Cd

1.2

170

4.24

8.15

****

Vivanco TBM-4126

Ni-Cd

1.2

160

4.18

7.58

***

Yokohama MCT/11/B

Ni-Cd

1.1

152

4.26

8.29

****

 

KEY: Cap = capacity, in ampere hours (Ah), Run 1 = four 5-minute calls per hour, Run 2 = two 5-minute calls per hour’ rating, 5-stars best

 

* stated capacity 1.2mAh but fitted with 1.5mAh cells

** Standard Motorola battery, included as reference

 

BOX COPY 1

THE TECHNICAL BIT

You can skip this part if you don’t care for technical stuff but it’s quite brief. Battery capacity is measured in ampere/hours (Ah), generally speaking most standard phone batteries are rated at around  0.8Ah, which basically means that when connected to a constant load they can supply a current of 0.8 amps (800 milliamps) for one hour. In practice the load, or how much current the phone draws from the battery, varies widely, from just a few milliamps in the standby (switched on and ready to receive) condition, to several hundred milliamps when you’re actually making a call.

 

BOX COPY 2

CONTACTS

 

ANDREW Ltd, Ilex Building, Mulberry Business Park, Fishponds Road, Wokingham RG11 2GY. Telephone (01734) 776886

 

GRM Ltd., GRM Building, Copse Road, Fleetwood, Lancashire FY7 6RP. Telephone (01253) 773177

 

HAMA Unit 4 Cherrywood, Chineham Business Park, Basingstoke, Hants RG24 OWF. Telephone (01256) 708110

 

LINDEX UK Ltd (Chance Way), Unit 22 Beckenham Metro Centre, Kangley Bridge Road, London SE26 5BW. Telephone 0181-776 5775

 

ORA Electronics 28/29 Faraday Road, Aylesbury, Bucks HP19 3RY

Telephone (01296) 415445

 

TWINCHOICE Ltd., 153-157 Wadham Road, London E17.4HU. Telephone 0181-503 2613

 

UNIROSS Batteries Ltd., Unit 4, Blackfriars Road, West End Trading Estate, Nailsea,  Avon BS19 2DJ. Telephone (01275) 858101

 

 

---end---

Ó R. Maybury 1995 0908

 

 


 

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