Batt j14


#1

Hello,

Can we connect an external battery? It appears J14 on the electrical schematics. It references https://www.google.com/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&uact=8&ved=0ahUKEwicr5jboc7MAhUB3yYKHWsCBHAQjRwIBw&url=http%3A%2F%2Fwww.mouser.com%2Fnew%2Fmolex%2Fmolexpicoezmate%2F&psig=AFQjCNG8FsPlKeo6zpleVMOWTFkv1cJZvg&ust=1462926942649789
I found J14 labeled on the backside of the board (from a picture on the internet and on the manual. but don’t see a connector.


#2

Hi @queonda,

Thank you for the good question.

Yes, all the 96Boards CE specification compliant boards are able to power by an external battery.

Please refer the page 16 of the documentation of the LS connector.
http://www.96boards.org/ce-specification

The pin 36 and 38 (SYS_DCIN) are for the external power input to power the 96boards instead of the DC jack.

On page 8, to be compliant for all the 96Boards, the 8V to 18V power supply from the SYS_DCIN pins is recommended.


#3

Are they the same connection (electrically)? Some boards have an option for Power and backup power. This board does not have that option. IS there an addon board which can add this?

I’m looking for when the input power is lost, then the backup power will continue powering the device. Then you can give a timed shutdown not to corrupt the OS.


#4

Hi @queonda,

Yes, the positive center pin of the DC plug on the DragonBoard 410c and the pin 36 and 38 (SYS_DCIN) on LS connector are the same connection.
It is mandatory for the all 96Boards on the specification.

I do not see the Mezzanine board sold in the market to use this feature yet but it a good way to make the battery powered 96Boards.


#5

It is important to note that you cannot have power to booth the DC Jack and 36 / 38 SYS_DCIN pins simultaneously. The Dragonboard docs make that clear. So it is much better to have a redundant set of batteries and use a DC source to power the batteries for redundancy than to try and power both the DC Jack & the LS connector. Section 8.2 of the hardware manual for dragonboard says that very clearly. There is not an internal switch to regulate which port the power comes from.

I’m running multiple 3.7V batteries in parallel, with a step up converter to bring the batteries up to 12V. Then I charge the batteries when voltage gets low with a stepdown converter, from 5V to ~4.2V battery protection circuit. This way I can use a 2.4A USB wall-wart to charge the batteries, while the battery bank provides a clean 12V and enough amperage to keep the board alive for quite some time. In theory the board will not draw more than it needs, so having 10A + available in batteries is effective. This way I also draw power for other devices from the battery bank and avoid placing power hungry USB devices on the board itself.