I just burned my board

[pfeerick]

well , the minnowboard(another sbc,   http://www.adiengineering.com/products/m...rd-turbot/ ) also does not have overvoltage protection. there has been quite a bit of discussion on mailing list about damage due to user having plugged in something other that 5v and some have said that damage generally does not occur unless greater that 7v. like 9v. on the minnowboard the current takes out an IC  NCT3012S TR  which is primary voltage/current distribution and that particular chip is easy to replace thus bring most of the dead boards back. only if pine64 life was as easy. and this is power supply, not battery. so that is why i kinda question that a 7v, or 7.4v battery can cause real bad damage. maybe it can damage significantly at that voltage, it would surprise me. i mean we live in a world where a lot of 3.3v is tolerant of 5v. it would be nice if i was able to discern current flow from looking at a schematic chart, but i can't  

I'll try and break it down then... 

You have main three methods of powering the pine64 (in no particular order):

• From the microUSB. This is convenient, but has the issues of connector resistance, voltage sag in most 'el cheapo USB leads, and a design spec limitation of 1.8A. The USB spec allows the voltage to be as low as 4.4v, and as high as 5.25v. However, with SBC boards like this... anything below around 4.75 at the connector will cause you grief down the track. This input *should* accept up to around 7v depending on what other components are in the path. 
  
• From the battery. The thing to be aware of here is that this is a single cell battery - so 3.7v nominal (average), and it typically cycles between 3.0 when flat and 4.2v when full. If you connect power to the microUSB port, or the euler bus input (which I'm about to cover) the pine64s PMIC will also charge the battery. The thing to be aware of is that even though there is a three terminal connector on the battery - it is only a single cell, whereas a lot of three wire batteries you will come across are two cell (7.4v nominal), which the PMIC is certainly not expecting... It would probably accept up to around 4.4v without any issues (4.35v max + 0.5v tolerance). The reason for the different connector is the PMIC supports thermal battery monitoring, so the pine64 guys have chosen to use it (rightly so... if you consider the recent Samsung issues!)
  

• The other common (and sometimes preferred method of powering depending on your knowledge and intended use for the board) is the euler bus. You can connect approximately 5v (I run at 5.2v) to the two appropriate pins  (actually 4, but they are simply duplicates to share the load) there. This input *should* accept up to around 7v depending on what other components are in the path. You can look at the pinout diagram linked in my sig to see which pins are the DC_IN and GND pins for external power.
  

Now, the disclaimer. If you burn your board, not my problem :-P No, seriously... I haven't read the schematic fully yet, so don't know what other components are in the Euler in / microUSB power path, so don't know if something else will go pop if you choose to run your board at 6v for some reason. One thing to be aware of is with the Pine64+ boards, the input power also powers the USB ports when the jumper is in the DC_IN position, so running the board at a higher voltage than the USB spec will mostly likely kill an attached USB device. 

So, in a nutshell - if 7v had been connected to the euler buss, or the micro USB... I don't think there would have been an issue. But since it was connected to the battery connector, which at best would have been expecting just under 5v... it was not a very happy chip!