Making some external battery module instead of plugging a device to a wall

[John29]

I have an rfid reader (http://media.digikey.com/pdf/Data Sheets/ThingMagic PDF's/MERCURYDevKit.pdf) with these specifications: • In: 90-264 V, 0.4 A, 47-63 Hz • Out: +9 V @ 1.4 A • Max total output power: 12.6 W I would like to create an external battery module instead of connecting the reader to a wall. I would like to have some precisons on how to do it, which battery to choose and how long would the battery last ( I would like it's the run-time to be at least 12h)? Thank you very much

 

[flippineck]

Just to clarify, does the rfid reader itself expect a 9V DC power input? Looking at the spec sheet the 90-264V appears to be the power adapter's mains input, with the power adapter's 9V DC output being the power that's fed into the rfid reader itself?

I see it says "US, European, UK, and Australian plugs" but does that relate to the mains input to the power adapter?

What size and style of 9V DC power input jack does the rfid reader itself have (or is it solder pads, screw terminals etc?) - it does look like there's some kind of barrel type jack socket on the board

If it does use some form of plug-in power jack, e.g. a cylindrical one that uses a centre pin, is the centre pin positive or negative (it's usually positive but probably worth checking) - and what's the ouside diameter of the 9V DC power plug in mm if applicable?

I had a look on ebay for readymade solutions and found a whole bunch, mainly rechargeable lithium types, but 2 things to watch out for - some seemed extremely expensive for what they were, and also beware of the extremely cheap ones, I understand that some of these aren't made to stringent standards and are sometimes a fire risk

 

[davenn]

Just to clarify, does the rfid reader itself expect a 9V DC power input? Looking at the spec sheet the 90-264V appears to be the power adapter's mains input, with the power adapter's 9V DC output being the power that's fed into the rfid reader itself?

yes it does require 9V DC

 

[flippineck]

so working on the output specs of the supplied psu,

Out: +9 V @ 1.4 A • Max total output power: 12.6 W

you'd maybe need 3 pp3's in parallel to feed it for the thick end of an hour (off the shelf dry batteries a la supermarket)

But, the power drain is likely to be sporadic & highly dependent on actual usage, and better performing batteries could perform maybe twice as well

so not outside the bounds of possibilty that one decent lithium rechargeable pp3 could do the job for 12h if usage is light?