Looking at the schematic, it would appear possible to power the lime2 through the headers at 5v, is this correct or do I have to short the pads Marked 5V_E? Apart from lighting the power led what is the benefit (don't want to modify the boards if I can help it)
Thanks
No. It is not safe to power the board from the +5V pins of the headers. This would damage several FETs in the long run. The +5V pins are are only outputs and should never be used for power input. Only changing jumpers would not help.
The easiest modification that I highly recommend is removing (unsoldering) the black power jack and using its pads.
There are more complex solutions, but I believe some of these do more harm than good. Yet, if it is absolutely imperative to use the plastic headers for powering I can give you further advice.
Best regards,
Lub/OLIMEX
Which FETS?
I am not using the battery or charger-
I will examine the schematic again
Regards
FET4. But if you don't need battery then you can first close the jumper 5V_E (as you mentioned) and also remove FET4. Else it is kind of illegal situation for FET4 and would compromise the safety of the board. But if you remove it no more battery powering, nor USB powering.
Of course, you can keep FET4 and test how long it would last, do some serious measures and check whether there are problems.
I honestly believe that either using the pads below the power jack to solder wires or removing the power jack and using its pads on the top is overall easier solution that doesn't cripple the board.
Overall for everyone that might just stumble upon this question:
It is not safe to power a stock A20-OLinuXino-LIME2 board from the +5V pins of the GPIO headers. This would damage the board in the long run. The power pins at the GPIO headers are are only outputs and should not be used to power the board.