Nokia BP-4L Substitute Battery Test

By on Dec 14, 2009 in Reviews |

As mentioned previously on my blog, I use a Nokia E55, which uses Nokia’s largest battery, the BP-4L. Now, if phone batteries don’t float your boat, then stop reading now. But wait, do you have a Nokia phone? Is it perhaps the E90, E71, E52, E55, N97, E72? Then if you are using any of those, would you like even more battery life? Well in that case, maybe batteries aren’t such a boring subject!

I’ve been testing an extended version of the BP-4L, sent to me for review from

The Nokia BP-4L besides the unbranded extended versoin

The Nokia BP-4L beside the unbranded extended version

Unfortunately this battery isn’t branded, which is normally of concern, but I was brave and tested it out for you all. Since this battery doesn’t officially have a name, I’m going to refer to it, only for this review, as the BP-4X. Nokia’s BP-4L is a 1,500mAh battery and Nokia’s Energy Profiler application reports it as having 1,536 mAh capacity. Whereas the BP-4X is advertised as having a 1,900 mAh capacity, although the Energy Profiler application reported it as only having 671mAh. Fortunately, this is in error, as my tests did show that it does indeed last a lot longer than the standard BP-4L!

I came up with two real world tests for the two batteries:

Light Usage
Defined as: Checking email via Wifi once an hour between 06:00 and 23:00. Checking Twitter once every 30 minutes (with TweetS60) via WiFi. Two hours of MP3 playback and 30 minutes of internet radio streaming via WiFi, each day, both via the loudspeaker. One 45-minute session of video playback. Frequent text messaging and no more than one minute of voice calling.

Heavy Usage
Defined as: Checking email via 3G once an hour between 06:00 and 23:00. Checking Twitter once every 5 minutes (with TweetS60) via 3G. Constantly running Google Maps with GPS and 3G. Four hours of internet radio via WiFi and two hours of MP3 playback, both via the loudspeaker. Frequent text messaging and up to 5 minutes of voice calling.

Battery life test results

Battery life test results

So, the good news is that the BP-4X does what it says it does, it extends the battery life you would normally get. Under light usage, it appears you’ll get more than a proportional increase in battery life, but the opposite is true for heavy usage. As the chart shows, I did these tests with a Nokia E55, so expect these numbers to be slightly different for different handsets. I would expect an always-connected N97 to last less than this, although using an E71, or even the same E55, much more carefully, you could get much longer. In fact, with very little usage, I have had this battery last for over four days in my E55.

Now for the bad news. For whatever reason, the voltage levels on this battery don’t work in the same way that the standard BP-4L does. This means that the battery meter on your phone’s screen is rendered useless (this is not true for the N97, see the update section below). There isn’t a steady decline (i.e. you see your battery bars depleting); the battery will show at full for days, then will just drop when the battery is near exhausted. Also, the voltage level drops dramatically while you are making a call. It is rather disconcerting to just get talking to someone and then have your phone telling you it’s on low power. After a while, I became familiar with how the battery behaved, and knew not to take notice of the warnings. However, this means that the job of the phone’s battery meter becomes your own responsibility: you need to mentally keep track of how much you’ve used it, when you last charged it, and for how long.

There you have it, it is impressive that you can get so much more energy stored in a unit that is exactly the same size. Most extended batteries for other phones require you to have a bulky custom cover sticking out the back of the phone. At around £12 the price isn’t bad either. The disadvantages come with having to ignore low battery warnings when you’re making a call, and seeing full power when it’s nearly exhausted, instead mentally keeping track of how much you’ve used it. Being unbranded, it’s quality is also of concern, although I can say that after a month my phone has suffered no ill effects from using this battery.

If you need a spare battery when you’re going to be away from a charger for a while, then this is definitely worth a look.

Update 12th March 2010

Thanks to Nokia PR and, I have been fortunate enough to borrow an N97. I’ve tried this battery in the N97, and the battery meter works properly.


Day 1-2
Battery withstood normal usage but reported low power during calls.
Battery level (voltage?) recovered a while after call ended.

Day 3
Finally completed first discharge by using iplayer for over an hour.

Day 4.
Fully re-charged, and topped up, ran twitter, email and google maps for
six hours, then internet radio (wifi) for 4 hours. Battery still showed
full level.