Battery lifetime of the N95 using TruPhone, GizmoProject or Fring

Most people seem to be unaware of the difference in powerconsumption between wifi and UMTS, especially in reference to TruPhone, GizmoProject or Fring.

I noted earlier that I can have TruPhone connected for several hours without a single powerbar dropping on my phone. Other people however report otherwise. Surely their phones are not broken :-P. Also there is the question of difference of powerusage between Fring with its own SIP-stack and others like Gizmo or TruPhone which use the in-built SIP-stack, although perhaps with different compressions.

So I tested today fring at work, logged on for 5 hours and 39 minutes using wifi. Left my phone to its own and worked ;-) And yes it was also online via GSM, reception was 3 bars on the 1800 MHz network. Would't miss my calls. The connections figures are

Signal Strength: 97-100%
TX-power 100mW
Transmit/Receive: 2.14MB/89.27kB

After more than 5 hours not a single powerbar dropped! Some easy calculations on the battery capacity versus wifi power gives some interesting numbers. A contineous powerdrain of 100mW on a fully charged battery should last about 28 hours until it is completely drained, assuming the phone draws otherwise none. And with a standby time of >228 hours this is comparatively so. Power efficiency certainly would be less than 100% but then the wifi is never contineously used at that moment to its full. The transmit/receive is less than 2.3 MB in total a fraction of the possible data amount at contineous transmission. Standby should really outlast the 28 hours several factors even considering some cpu-load for the whole action. It can hardly be more than the drain on the phone for regular calls. How then explain these huge powerdrains other people complain about?

Wifi goes up to 100mW worst case.  Running Voice calls over GSM, GPRS or UMTS however requires far larger power transmissions than wifi. It will take anything from a tiny 1 mW  up to nearly 1 Watt depending on distance to the groundstation. 1 Watt versus 100 mW would drain your battery about 10 times faster! Resulting in 2.8 hours and that number happens to be very close to the N95's WCDMA talktime as specified by Nokia ;-) So yes, there goes the power. Looking at one of my earlier blogs about battery life of the N95. The figures for the P990i show that UTMS and GPRS even have a far larger power demand than voice GSM. Mostly because they don't wat to drop some bits and bytes. Where as a voice call over GSM doesn't care to much about it.

The trick is to use SIP and InstantMessaging when you are stationairy near a wifi-point. Or very close to a cell station!

Make sure you have read my post: Battery life of the n95, the facts.