An updated version of Murphy's Law probably states that your cell phone battery will die on you when you need it the most.

A Cellboost emergency battery plugs in to your phone and recharges its battery, giving you plenty of extra talk or standby time.

Cellboost instant battery charger for cell phones

The Cellboost disposable battery charger comes in different models, each with a different plug to fit a different type of cellphone. They are very easy to use - just plug them in to the phone.  They are also relatively inexpensive - street prices of about $6 each. Best of all, they work as promised, giving 60 minutes or more of extra talk time, and up to 60 hours of standby time. Unfortunately, they're also limited to only a single use.  Our own Clipper Gear Cell Phone Emergency Battery Recharger is probably a better choice for most people and situations.

Now you no longer need to be always charging your cellphone, even when the battery is still half charged.

Just slip one of these small and inexpensive Cellboosts into your pocket and you're protected if your battery dies on you.

What you get

Each Cellboost is packaged on a plastic card, but mercifully it is easy to open and get it out - there are perforated tear lines on the back of the display card.

The unit measures slightly over 1¼" x  2", and is just under ½" thick.

A protective cap (color coded for different phone types) protects the plug that sticks out of the top of the unit, and brings the total length of the unit up to about 2¾".  Each unit weighs a negligible 1¼ ounces - you could fill your pockets with these and not notice their weight!

There are almost no instructions with the unit (and no real need for instructions, either), other than a suggestion to wait two minutes before turning on a cellphone if its battery is completely dead, and to unplug the Cellboost after 60 minutes.

Each unit shows an expiration date on it.  The several that I got in early 2003 all showed a September 2006 expiration, suggesting that the batteries inside the Cellboost units last about 2.5 - 3 years.

How it Works and What it Does

Plug the Cellboost unit into the charger socket of your cell phone, and it starts transferring its charge from its internal (non-rechargeable) batteries into your cell phone.

I tried Cellboosts with three different brands of phone and type of plug (Siemens, Nokia and Motorola).  In all cases they plugged easily and firmly into the phone's charger socket, making it possible to use the phone while the Cellboost was plugged in to it, so you can start using your phone again within seconds of plugging in the Cellboost.

The display card boldly states the capacity of the Cellboost unit, giving 60 minutes of talk time or 60 hours of standby time. A small asterisk directs you to the necessary fine print which explains that these are average times, based on phone model and optimal conditions.

This made me very skeptical.  I've never yet bought a cellphone that actually has as much battery life as the manufacturer claims, and this 'optimal conditions' phrase reminded me strongly of claims by FRS and GMRS radio manufacturers about their range capabilities - claims that my testing showed to be exaggerated almost ten-fold in non-optimal conditions!

So, with considerable curiosity, I set about testing these units, expecting results way below the stated claims.

Test results

Test 1 - Nokia 3650

I discharged my Nokia 3650 until the battery was so dead that the unit switched off and wouldn't restart.

I then plugged in a Cellboost unit.  With the phone still switched off, I charged it for two minutes, then turned the phone on, and placed a phone call.

I left the Cellboost connected into the bottom of the phone, and timed to see how long I could talk on the call before the battery died on me.

The signal strength for the T-Mobile GSM service I was using varied between 2/3 and maximum as I moved the phone around a bit, to try and create a realistic use environment.  I also had the phone's Bluetooth switched on (this drains the battery faster than if it is off).

After 52.5 minutes, the phone died.

This was more than satisfactory, and closer to the claimed optimum performance than I've ever experienced with cell phone batteries before.

But, wait - there's more!

Although the Cellboost instructions said not to leave their battery plugged in for more than 60 minutes, I left it plugged in, with the phone off.  After 12 minutes, I turned the phone back on again, and made another call.

Incredibly, the phone lasted another 27.5 minutes before the battery died and the call was disconnected.  This made a total of 80 minutes airtime, using a phone that chews through battery life at a rapid rate.

And, I'm still not done.

I still had the Cellboost plugged in.  After 5 minutes of charging the dead phone, I turned the phone back on.  At this point, the phone told me it was no longer getting any more charge from the Cellboost unit, so I unplugged it.  The phone continued to work on standby for another 30 minutes before I gave up waiting for it to die again.

Incredible.  Much better than expected.

Test 2 - Nokia 3650

I took my fully discharged 3650 and recharged it again with a Cellboost, leaving the Cellboost connected to the phone for an hour.  Then, in an attempt to recreate a typical day of usage, I made several short calls with periods of standby in between.

I was able to get 10 hours of standby time and 16 minutes of talk time out of the charge from the Cellboost.

The good news - this is probably enough to get you through the rest of a day until you can get to a charger if your phone dies on you early in the morning.  But it seemed to be rather less than the 60 minutes or 60 hours promise indicated.

Test 3 - Motorola V66

I discharged the battery in my V66 until it was so dead that I couldn't turn the phone on.

I then plugged the Cellboost unit into it, waited two minutes, and then turned the phone on and made a call.

My test with the 3650 was intended to be a tough test - with only fair signal strength (the weaker the signal, the more power is used to send out the radio transmissions).  And the Nokia 3650 was set to use a lot of power, more than most other phones would.  Even so, in this tough environment, I got 80+ minutes of talk time.

I now decided to make the V66 test a 'best case scenario' - the lovely tri-band V66 that I purchased from Telestial is a very light power user, and so I expected it to last at least an hour and maybe even more.

I left the phone in an area with perfect T-Mobile GSM reception, and turned off all the other current draining features of the phone.

You'll remember that Cellboost promise 60 minutes of talk time in optimum conditions.  Guess how long my V66 call lasted before the battery died?

Not 50 minutes.  Not 60 minutes.  Not 90 minutes and not 120 minutes.  I got a staggering 155 minutes out of the call!

This is amazing.  A device that is 250% better than the manufacturer claims!  However, while the Cellboost's performance is very credible, the Clipper Emergency Recharger provides more than twice as much power and so gives better emergency backup.

Facts and figures

With a new Cellboost unit (for my 3650) I measured its voltage.  Fresh, the unit was giving off 6.33 volts, and when first connected to the phone with a nearly flat battery, it was pumping about 350 mA of power into the phone.

Both voltage and current rapidly dropped off, within three minutes only 250mA of current was flowing into the phone, and after 7 minutes it dropped to 150 mA, a level that stayed reasonably constant for the future.

By the time the Cellboost had just about all the charge sucked out of it, the voltage had dropped down to 4.83 V.

The standard Nokia wall charger feeds in power at a much greater 795 mA, at a notional 6V.  This discrepancy is a good thing - it means that the Cellboost units are not harming the expensive battery inside the cell phone; a fact that I also empirically confirmed by checking that the phone's battery didn't get at all hot (heat buildup during charging means you are seriously harming your rechargeable batteries).

Getting the most from your Cellboost

The batteries inside the Cellboost recover some of their strength after they have had a break from charging your cell phone.

The best idea is to charge your phone with the Cellboost for about 20 minutes.  This will probably transfer about half the power from the Cellboost to the phone.  Then, when the phone dies again, plug in the Cellboost unit again, and after another 20 minutes, you'll have transferred perhaps half of the remaining half charge.

And so on.  In a total emergency, even a completely dead cellboost unit, that can no longer charge a phone, will still recover a small amount and give a precious minute or two or three of power before dying once more.  But normally, you'll probably choose to replace your Cellboost after a couple of short (20 minute or less) chargings.

A look inside the unit

Reading the publicity materials supplied by Cellboost, I came across the statement

Cellboost has a unique means of instantly providing talk time and charging for cellular phones

This intrigued me.  A 'unique means'!  Although the instructions warned not to open the unit, I fearlessly went ahead and opened up a Cellboost to see what unique technologies were inside.

Ummm.  There were four small batteries joined in series (to provide the power) and a 2 ohm resistor also in series (to provide a simplistic and inefficient voltage control).  Nothing else.

Unique?  No.  But, the simplicity of the unit is not a bad thing, and in no way detracts from its functionality.

Cost

The Cellboost units generally cost the same, no matter which model type you get (the only difference is the adapter on the top, which varies to fit the different cell phone charger sockets).  I've seen them for sale as low as $6 each at PCMall.com.  They're also available at a growing number of electronics and phone retail outlets.

Summary

Sometimes your cell phone can be an essential tool to help you resolve an urgent problem.  At such times, you can't afford to have your battery die on you.

For only about $6 each, carrying a Cellboost with you means that, no matter what else might be going wrong around you, there is no danger that your cell phone will die.  You'll get enough extra battery life to spend an hour (or perhaps more) on the phone, or to have a mix of talk time and standby time for close on an entire business day.

The Cellboost is small and light, simple and inexpensive, and works perfectly.  On the other hand, you need to have different Cellboosts for every different type of cell phone you might have in your office or family, and after using them once, you need to throw them away and replace them.

Our Clipper Gear Emergency Cell Phone Recharger uses inexpensive AAA batteries, and has multiple adapters for different phones, making it generally the better choice for most people and situations.

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Originally published 23 January 2004, last update 21 Jul 2020

You may freely reproduce or distribute this article for noncommercial purposes as long as you give credit to me as original writer.