The Smartphone Extended Battery Scam

Smartphones have become so powerful they are practically like miniature computers you could slip into your pocket. You could listen to music, browse the web, or play games on them.

However, the power comes at a cost: poor battery life. Last-generation feature phones (or  “dumb phones”) could easily last a week between charges. You would be lucky if a smartphone could go a whole day without recharging.

You can find many tips to conserve your battery life. There are three main sources of energy consumption, namely the screen, wireless connections, and CPU processor. Saving energy means toning down your usage of these three items.

1. Screen: If you turn on the “automatic brightness” option, the smartphone will adjust the brightness according to the light level of your environment. Better yet, you can turn down the screen brightness manually to the lowest level you can tolerate.

2. Wireless connections: The newer 3G/4G/LTE connections are fast but sap battery power quickly. You can switch to the slower 2G to save battery.

Alternatively, limit the time these connections are on. Smartphones constantly check for new data (or “synchronize”) from the server. You can increase the time period between synchronization, or better yet, do it manually by turning off the “autosync” option. Wi-fi and GPS also eat up lots of energy, so turn them off when not in use.

3. CPU: This tip is for advanced users. If you have hacked your phone to gain high-level root access, there are apps to lower the CPU speed and voltage to reduce power consumption. The slower the phone, the lower the energy needs.

Apps such as Juice Defender can help you do the above steps easily.

Now, these tips do work, but it’s just silly. Why should anyone buy the latest quad-core smartphone with a huge bright screen, and then disable all the best things about it?

Extended batteries

The best solution is an extended battery. These are higher capacity batteries which allow the phone to run for longer. A simple brute force approach, but it works. Unfortunately, most manufacturers do not produce official extended batteries.

Even if they do, the extra capacity is usually less than 20%. For example, the Samsung Galaxy Nexus has a 2100mAh extended battery, which is only 13.5% more than the original 1850mAh battery.

Where there is an urgent need which manufacturers are not meeting, third party companies jump into the fray. The big players in the extended battery game are Mugen and Seidio. You can get Anker and Chichitech batteries from Amazon. Finally, there are also many unbranded batteries available on Ebay.

These third-party batteries often promise double the battery life. I bought a Trexcell 3500mAh extended battery, which is double the original 1730mAh for my HTC Evo 3D.

Trexcell 3500mAh extended battery for the HTC Evo 3D

How to charge an extended battery?

It came with some instructions: I am to drain the battery completely before charging it. Once it reaches full capacity, I am to charge it for a further 2 to 3 hours.

Apparently, the draining helps to calibrate the battery by letting the smartphone know the battery level properly. If poorly calibrated, the smartphone may think the battery has run empty even when there is juice left.

The “top-up” charging is ostensibly to ensure that the battery is fully charged. Each smartphone was apparently designed to work with a specific battery capacity, 1730mAh in my case. So this extra charging will help charge the battery beyond this limit.

Is it a scam?

To my skeptical mind, if the battery doesn’t work as promised, the manufacturer can simply say that you probably didn’t follow the above instructions properly.

They could always say it’s your fault for not conditioning the battery properly, and there is no easy way to prove them wrong. Most buyers will either meekly accept the explanation or shrug it off as an unlucky lemon. At prices starting from around USD10 per battery, most won’t bother with a refund.

My personal experience

I duly discharged and recharged my Trexcell 3500 as instructed. But the battery life didn’t seem much better than the original battery. On some days, it seemed to work wonderfully. There was once the battery indicator stayed at 85% for two hours, despite browsing the Internet for at least 10 minutes during that period. On other days, it lasted barely 8 hours of light use.

Was it a faulty indicator? Was any improvement due to battery saving tricks? Was I unconsciously using the phone frugally to save battery? Was it just the placebo effect?

The first thing I did was to install the Battery Monitor Widget Pro, available from the Google Play store. It is a tool for managing your battery, and displays different information such as voltage, discharge rate, and capacity.

Below is a temperature graph:

Battery Monitor Widget Pro – temperature graph (Trexcell 3500)

The middle portion in red is when I swapped in the Trexcell 3500 battery; I used my original HTC battery before and after.

Notice how the temperature of the Trexcell oscillates regularly between 24 and 25 degrees? The original battery, on the other hand, shows much more variation as might be expected from normal use.

This is the first clue that the Trexcell battery is probably fake.

Let’s take a look at another graph:

Battery Monitor Widget charging graph (original HTC)

The outlined portion shows that the battery stops charging at full capacity. Charging restarts when the battery drains to 95%. This function prevents overcharging of the battery, which causes it to degenerate over time (I’m not sure if only HTC smartphones has this function).

This means that charging after the battery is full, as Trexcell recommends for the extended battery, actually achieves nothing.

Perhaps an external battery charger would work? I searched high and low before I found a suitable charger. It’s an universal battery charger which fits all brands of batteries.

ABS universal battery charger

It has two movable pins, which you can adjust to fit any smartphone battery. The battery has 4 metal plates, the pins should fit the 2 plates matching the “-” and “+” symbols (in this case, at the ends).

4 metal plates of the battery

The polarity doesn’t matter, but fitting the battery in under the clamp does take a bit of jigging.

So I charged the Trexcell extended battery again, this time in the external universal battery charger, and left it in for an extra 3 hours after the charging light has stopped flashing.

Despite this, the battery life is still dismal, lasting fewer hours than the original HTC.

By now, I’ve read that many sellers of extended batteries exaggerate the claims of their batteries. Some have taken the sticker label off to find the true capacity printed on the battery. I tried the same, but the capacity was not listed inside.

Computer Battery Analyzer

The only objective way to find out is to use a computerized battery analyzer (CBA). I searched around the Internet and it seems that the CBAIII sold by West Mountain Radio seems to be the most popular option.

CBAIII by Optim Engineering

The consumer version is USD150 while the pro version is USD200. The difference between the two seems to be the level of accuracy. I decided to get the pro version. Even with the UPS shipping from USA, it was still cheaper purchasing online (USD240 or around SGD312) than buying from their Singapore dealer SingaHobby (SGD365).

The CBA applies a constant load to a fully charged battery, and measures how long it takes to discharges to the cut-off voltage. From there, we can work out the capacity of the battery in mAh.

To do this test, we need to enter the cut-off voltage into the CBA software.

The nominal voltage of the Trexcell battery is 3.7V. But from the graph below, we can work out the effective voltage range the battery is operating in:

Battery Monitoring Widget – effective voltage range

The voltage ranges from 3.335V to 4.348V. The battery can power the smartphone effectively only if it’s above 3.335V. Therefore, I round the value up and put 3.4V as the cut-off voltage for the CBA discharge test.

The second value is the test amp rate. This is tricky because a smartphone doesn’t discharge the battery at a constant rate. Instead, the discharge rate is dynamic, ranging from around 10mAh when idling to over 500mAh when running intensive programs such as 3D games.

Battery Monitor Widget discharge graph

The lower half of the graph shows the discharge rates when the phone is in use while the upper half shows the battery charging. Based on the above graph, I estimated 250mAh to be the median value for the test amp.

I charged up the Trexcell battery fully and ran the test twice. Here are the results:

CBA capacity graph

The horizontal x-axis shows the capacity in mAh while the vertical y-axis shows the voltage. The test stops once the voltage dips below the cut-off value of 3.4V.

You can read the values off the x-axis: 814mAh and 828mAh.

Very disappointing, this is only 24% of its stated capacity (3500mAh) and less than half of the original HTC (1730mAh).

The Trexcell doesn’t hold its charge well at all. At the time of testing, I have used the Trexcell battery for about 2 months. I didn’t have the chance to test it when new, but its performance has definitely degenerated dramatically in the past few weeks.

The CBA also comes with an optional temperature probe.

CBA temperature probe

The temperature reading was around 27 to 28 degrees. This indicated that the Trexcell battery was rigged to send false temperature readings to the smartphone.

[Update: 1 May 2012] HTC Evo 3D 3500mAh from Tmart

I had ordered an extended battery from Tmart but it only arrived after I had offloaded my HTC Evo 3D phone. Never mind, I have another test subject.

HTC Evo 3D extended battery 3500mAh from Tmart

I subjected it to the same discharge test as for the Trexcell, again using 250mAh as the test discharge rate. Here are the results:

CBA HTC Evo 3D Tmart 3500 discharge test

The battery clocked in at 1507mAh, which was 43% of its rated capacity. It’s currently higher than the Trexcell but we can expect its capacity to drop drastically over a few months of usage.

The starting voltage is only 3.95V, which is considerably lower than the 4.24V of the HTC official standard battery. Again we see the steep dropoff towards the last third of the test. This battery has problems holding its charge.


The extended battery industry is fertile ground for scams. So many factors affect the battery life, and few people would go to the extent of using a computerized battery analyzer. It is easy to be misled by fraudulent claims of great battery life.

I bought the Trexcell battery off Amazon for around USD15. Don’t be fooled, it is not the bargain you had hoped for. Don’t waste your time and money on third party batteries.

Only buy official batteries. If no official extended batteries are available for your phone, just buy a spare battery and use your smartphone the way it is designed to be used.

Further reading

This blog post was inspired by BatteryBoss.

About Hun Boon

A little bit of this, a little bit of that.
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4 Responses to The Smartphone Extended Battery Scam

  1. Pingback: Surprise, some extended batteries actually work! | Hun Boon's Blog

  2. Josh says:

    Nice information here! I have this same phone, and have been peeking around the market for a wile now. Seem like Seidio is the only good brand iv heard about, yet the only (old) tests i found on them also suggested false claims. the battery im wondering about has such wonderful reviews though, the 4000mAh one with a $70 price tag. I dont expect to come through all the way on those claims, but now i want to see a review similar to this one before i purchase. why did you ditch the evo 3d, and whats your current phone?

    • Hun Boon says:

      Well, high prices and well known brands are no guarantee of accurate battery life.

      I’m using a galaxy nexus now, loving the high resolution screen and jelly bean! 🙂

  3. Om Shankar says:

    Sir, no matter how many tests you do or how many calibration/full-cycle instructions you follow, the maximum capacity of the battery remains same.
    So if the seller promised you 3500mAh, then that value can be tested and remains the same.
    If you get 1800mAh max capacity in battery monitors for the same battery, then that’s it, its a fraud battery.


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