Problem solved, thank you all!!
Hi everyone,
This forum & thread really saved me of throwing my Iphone 3GS (with jailbreak and unlocked by software) and unnecessarily buying a new smartphone!
As a lot of people describe here, I was also having erratic blackouts without other solution than connecting to the charger to immediately have the iphone going back to life:
### If my Iphone was on standby mode, the battery lasted a day easily and without sudden blackouts. Along the day the percentage was moving from 100% (when full) to 20% at night (I didnt use to let it drain completely).
Certainly the battery was lasting less than its glory days but not so much to say the battery was defective and causing the whole trouble!
CLUE1: However, during the day when checking if new emails/calls sometimes I realized big leaps of the battery consumption percentage. But I didnt pay real attention and instead explained with: + several apps running in background, +long time running without a reboot, +a need of calibrating the battery, etc.
### On the other hand [actively using the iphone]: At the very beginning of the problem, it could work without blackouts and other times it gave me the blackout after 20 or 30 minutes at any given battery percentage. Because that, I started getting suspicious about apps (corrupted, causing a conflict, not compatible with my old 3GS
you name a reason). Other times because the blackout happened during a call, I started blaming the unlock app, and when it was a frequent issue, I thought the jailbreak caused the problem somehow.
In other words, because the random timing of the blackouts and what exact action I was doing in the phone when they happened, I was paranoid about everything related to software but not the battery.
When the problem got worse, the available time reduced to 2 to 5 minutes before the deadly black screen.
CLUE2: I must say when the iphone was plugged to the charger, I was able to use the phone as long as I wanted.
When I finally got a chance to execute a full restore (because it was a software problem right??) It didnt get better. Thats what brought me to this thread and the battery as the cause of the problem.
Short story, thanks to the info posted here, I decided to buy a new battery: mercadolibre.com.mx $150pesos + shipping (I am from Mexico). I replaced it, did a full restore as suggested and after several full charge/discharge battery cycles (to let iOS correctly calibrate the battery), I can happily say the blackouts are gone: I can use my iphone as long as I want and do whatever I want
The paranoid and dont disturb the iphone too much days are gone!!
For those that purchased a battery that did not resolve the problem or got a lemon APN, my experience was: I took note of the APN numbers discussed here to know the good one to buy (or do NOT buy) BUT all the sellers didnt care APNs
so the best I got was a generic 1600mah (APN printed nowhere). Maybe I was lucky, but please give several full charge/discharge cycles to the battery to get accurate percentage indicator. You might have a good battery with your iOS incorrect calibrated.
Next time the iphone turns off (blackout) suddenly, instead of blaming software I will begin paying attention to the battery
Thanks a lot to all the people bothering to share their symptoms, their action plans and their results. You are the best.