Full-Powering OlinuxIno-Maxi by ONE 3.7V Li-Ion accumulator

[flavigny]

Hello,
CAUTION: I don't have sufficient knowlege to validate it, so consider this post as a proposal or testimonial, no more!
components:
- LiIon pack with 2 PROTECTED 18650accumulator: 8.5 $: http://cgi.ebay.fr/ws/eBayISAPI.dll?ViewItem&item=280970013189
- Dc-Dc step-up: 3$: http://www.ebay.com/itm/DC-DC-3V-to-5V-9V-Voltage-adjustable-step-up-Power-Transformer-Module-40-85-/251154128233
- Holder: http://cgi.ebay.fr/ws/eBayISAPI.dll?ViewItem&item=150763929115
- breadboard (1.5 $!): http://cgi.ebay.fr/ws/eBayISAPI.dll?ViewItem&item=270973557315
- Usb-to-5.5 mm power cable: cgi.ebay.fr/ws/eBayISAPI.dll?ViewItem&item=180970043814

for testing:
- voltmeter: 2$: http://www.ebay.com/itm/LED-Panel-Meter-Mini-Lithium-Battery-Digital-Voltmeter-DC-3-3V-17V-/330807982367
- multimeter (Ampere meter)

here is the work:


as you see, accumulator rather empty (3.6 V range from 4.0 to 3.2), current is 500 mA
I use O'Maxi, with ethernet, TTY debug, Usb (via powered hub)
I set output Voltage of Dc/Dc converter at 6V (without load)
Input current is 400 to 500 mA.
BTW input current to O'Maxi is 230 to 280 mA
OlinuxInoxMaxi runs 3 hours; it is very less than the 10 hours expected (capacity of 4000 mAh divided by 400 mA). I will continue to investigate it.

NOTE: also possible: "universal" version using up/down converter (15$): http://www.ebay.com/itm/DC-DC-Converter-Regulator-Step-up-Step-down-2-in-1-/370538642812
Regards
PO.

[stefan]

Flavigny,

According to Philippe Mangaud, FAE at Freescale France, the best power efficiency is obtained when powering iMX23/28 with "fake" 4.2V battery as it reduces a lot the heat up of IC.

Kind regards,
Stefan

[flavigny]

Hello,
could you precise if this may be applied to O'Maxi or it is to be considered in designing a new board?
reading the schema (manual rev J, page 32) is it possible to:
- cut jumper 5V_E
- connect 4.2 V (stabilized) to pin +5V Ext ?
Regards
PO.

[stefan]

I would suggest to:
- remove 5V_E jumper connection
- connect 4.2V stabilised power supply to LIPO_BAT Terminal
Caution ! I don't have Maxi board and haven't tested that !

KR
Stefan