Nokia 6185 and 6188 Battery Tests

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		It seems that the 6185 and 6188 don't live up to their promised battery life. I've had many people ask me what sort of life I get out of my batteries, so I have undertaken a series of controlled tests to find out. Last Updated: 29-Jun-1998
	6188		6185

Types of Tests Performed, and Methodology Used

My first test determined the talk time of a fully charged BLS-2 battery. I didn't actually talk with anyone during this test, so I had to take steps to ensure that the pseudo-call conformed to conditions under which the phone would most commonly be used.

The first problem concerned signal strength, since where the phone was tested would have a strong impact on the battery life. CDMA systems tightly control the output of the phone so that everyone's signal arrives at the site with the same relative strength. Phones very close to the site would transmit with tiny amounts of power, while those approaching the limits of coverage would transmit quite close to the 200 mw power output limit. I chose a location which had an incoming signal strength of approximately -90 dbm and a corresponding transmit power level of +13 dbm. This would most likely approximate real world usage, though results would certain vary, depending upon where you used the phone. Out on major highways would probably result in better battery life than usage inside a poorly covered shopping mall.

The second problem concerned speech patterns during the call. CDMA phones drop their VOCODER rate when you aren't talking, and thus they use far less power than when you are talking. I decided to simulate a 50% talk cycle, and I did this by playing Environment Canada's weather broadcasts into the microphone. I could then turn up the volume, or turn it all the way down over timed intervals during the test.

For testing standby time, the methods used are far more straight-forward. I simply reset the timers each time I charge the battery and then I used the phone normally until the first "Low Battery" warnings appear on the phone. The timer tells me exactly how much talk time was used. I have yet to make enough of this latter type of test to report a realistic standby figure, but it looks like it may fall somewhere in the range of 40 to 60 hour range once corrected for used talk time. I will discuss this latter point below.

Results of the Transmitter Test

Only one transmitter test has so far been performed, but I don't have any reason to believe that results of further tests would differ much from this one. During the call, I watched when the battery level indicator dropped from 4 to 3 bars, from 3 to 2 bars, from 2 to 1 bar, and when the first "Low Battery" warning kicked in. The following chart shows the results of the testing:

As you can see, the battery meter is fairly linear, though it does seem to drop to 3 bars more quickly than it should. This result of 2 hours comes in at the low end of Nokia's talk time estimate, but given the "average" conditions this represents, I would have expected to see an additional 15 to 30 minutes of talk time. However, the results are encouraging, and I would fully expect much greater than 2 hours of talk time if the phone is used in stronger signal conditions.

Correcting Standby Times Based on Talk Times

When I carry out the standby times tests, I will inevitably have a certain amount of talk time in there too. Any time spent talking on the phone will reduce the standby time, but now that we have a reasonable idea of the average talk time per charge, we can compute the scale factor for talk vs standby. Say for example that I observe 25 hours of standby time along with 1 hour of talk time. Since one hour of talk time represents approximately 50% of the battery life (see the above results) then we can extrapolate a pure standby time of 50 hours. I will use this method of testing, and I will post each standby result here as it becomes available:

This certainly isn't anywhere near the 70 to 110 hours promised by Nokia, but it isn't all that bad either. One this I did find was the psychological effects of having the phone display "1 bar" for so long. The display is very linear, but I think we would probably feel better if the meter stayed at 3 or 4 bars for a disproportionately longer period of time than 50%.

Analog Battery Times

Quite a few people have complained about exceedingly short battery life in analog mode. I had the pleasure of testing this in real life when I went out of the city just recently. Lo-and-behold, I only managed to get about 6 hours of standby in analog mode. I had however, noticed that the phone frequently rescanned the CDMA bands to try and find a digital signal, and it seemed to keep doing this all the time. I therefore tried another experiment in which I forced my 6185 into analog mode. When I did this, I managed to get 13 hours of standby in analog mode. I thought this might be the trick, but the next time I went out of town (up to Midland) I forced analog. Unfortunately I got only 7 hours of standby there, so the test in which I got 13 hours may have been unfairly conducted.

If you plan on using your 6185 or 6188 in an analog area for a prolonged period of time, I suggest getting the higher capacity battery, or brining along a spare. I don't know if Nokia will be able to fix this, but I suspect they will. A software upgrade is expected in Demember, so we'll have to wait for that and see what happens.

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