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Power Consumption of a Psion S5 8MB with CF

Used material

Psion 5  classic, 8 MB RAM, ROM Version 1.01
Compact Flash Card: Hitachi 45 MB
2 Alkaline AA batteries
Digital multimeter


Current Drain (mA)

S5 State with CF
Power Supply
with CF
no CF
Off 13,7 0,7 0,7
On, only System active 41 28 25
Loading Word 97 84 81
Word idle 41 28 25
Word, fast typing 97 84 81

Additional functions:




Link on, idle: + 14 + 14 + 14
Link on, Rx on C: + 69 + 69 + 69
Link on, Tx from C: + 43 + 43 + 43
Light on: + 53 + 53 + 53
infrared on, idle: + 1 + 1 + 1
infrared on, Tx, Rx: not tested not tested not tested

"+" means: additional current drain, when the additional function is activated.
Rx=receiving file       Tx=transmitting file

Power consumption during Read/Write cycles

Running DiskBench V1.1, the average time and battery current drain, while reading or writing on C: (RAM) or D: (CF) was:
C: sec C: mA D: sec D: mA
Write 1MB 0,54 84,5 5,5 72
Read 1MB 0,31 92 1,57 94

Reading and writing of a 1MB data file consumes (power consumption of "on, idle" state not included):
C: µAh D: µAh
Write 1MB 8,5 67,2
Read 1MB 5,5 28,8

Battery current with power supply attached

This section was added on 12.11.2004. Measurement done here with an Ericsson MC218 = Psion 5mx.

Some people supposed a small battery charging current with the Power supply attached. This is a myth. Here is why:

If I connect my MC218 to the Original Psion power supply and measure the current INTO the batteries (fresh alkalines, having 3.04 Volts without load): the current is -0.059 mA or 59 µA flowing OUT of the batteries - no charge, but a slight discharge!

I repeated the test with 2 NiMH rechargeables of 2.71V (unloaded voltage): 50µA going OUT of the batteries with the Psion switched on.

Interestingly, this current rises to about 52µA when the Psion is switched off.

If I disconnect the power supply the current rises to about 1.1 mA OUT of the NiMH. This value corresponds with the 0.7 mA of the S5 above. This is the current taken day and night from the batteries when the Psion is switched off. It will rise somewhat when the voltage of the batteries drops over time.

So, if you want your rechargeables being recharged while still in the Psion, go to www.elektronikstore.de/psionstore . They do all kind of repairs and amendments to your Psion, including a charging circuit. (I am not related to this company).


All values approximately.
Use all these figures AT YOUR OWN RISK.
I reject all responsibility for any conclusions whatsoever.

These figures are SMILEWARE:
If you like this data, give someone a smile for each time you use it,
or do something nice for someone else for each day you use it.

Comments welcome; re-use with source.

Copyright İ Ulrich Hornstein, Freiburg, Germany.


Data from 15. Feb 1999. Chapter "Battery current with power supply attached" from 12.11.2004.

Interestingly, this measurement has been used by IBM scientists on research for: Energy trade-offs in the IBM Wristwatch computer. This research article was in use in a course for advanced computer archictecture at Harvard (fall 2003, Dec 8).

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Stand / Last Revision:  12.11.2004  (18.02.01)

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