Battery-powered, good news
In previous blog posts, I shared my disappointment because I wasn't able to have a decent battery life, when trying to power the RaspberryPi with battery. I couldn't get more than 1.5 hours with a 18650 battery (for those who don't know these: it's a 3.7V battery, a bit larger and higher capacity than standard AA batteries).
I was a bit sad because this meant to have to abandon the concept of portability, of being able to play outside with SamplerBox. Or to have to go for solutions like using many batteries (2 or 4) or big USB powerbanks, and I didn't like this idea. I didn't like it for this reason: a smartphone is able to run for one day or more, also runs Linux (Android uses Linux kernel), with a very small battery, so I wanted to be able to find a similar solution in terms of battery-size and battery-life, with a RaspberryPi.
Now there's good news.
Today I did some new tests, with a new 18650 battery that I bought from PuissanceLed. Waw, this guys knows what he's speaking about, he did some extensive benchmarks before selling his batteries! I chose the "Sanyo 3400 protégé", which costs 13,50€.
And the result is great: the RaspberryPi ran for a little bit more than 7 hours with a single battery, before it shut down (and tried to reboot, but the battery was empty).
Why was the result so poor (only 1.5 hours) with the previous 18650 battery that I tried? Probably because it was a cheap fake 18650 battery from eBay. My conclusions here about this subject.