SODAQ SARA AFF N211 Battery 3.7v , the 5V pin dose not give the voltage

SODAQ SARA AFF N211 Battery 3.7v , the 5V pin dose not give the voltage.

Problem is , if i connect through USB the 5V pin works fine and sensor for 5V works great.

When i disconnect the USB power supply , and connecting the 3,7V accumulator , the 5V pin dose not work , when i test there’s 0V.

What could be the problem and is there a way to enable 5V ping to work with 3,7V battery?

3.3V Pin works properly with Battery , but not all sensors support that low voltage, so 5V is needed

any solutions to get 5V sensors working are welcome!
as solutions i see :

  1. throw out 3,7v battery, get additional circuit with higher voltage battery to supply 5V output> connect to USB? or i can just connect to 5V pin?!
  2. dose this board supports higher voltage battery? possible solution , to connect 6-9v battery if it is supported?!(or the 5V pin wont work also in that case)

As i see through USB the battery gets overcharged to 4V-5V, that is not normal, how would i charge the lipo battery properly if not through USB? or the board really needs a higher voltage…

In addition , if any information about Solar charging is available i would like to know.
What are the limits , Volts, Watts.
i have some panels would like to get it working together with battery.

Hi @Vitaly,

The 5V pin only works when there is a 5V power supply from the USB connector.
This is the way how we designed the board.
If you need 5V from a battery you need to connect an external voltage booster.

The battery is made for 3,7V (which is 4.2V fully charged)
You cannot attach a battery with a higher voltage then 5V when it’s fully charged.

A rechardable lipo battery never has the same voltage. 3,7V is the nominal voltage.
3.3V is empty, 3,7v = 50% and 4.2V = 100%.
When no battery is connected, you should measure 4,3V with a multimeter.
4,3V is the charge voltage.

The maximum voltage is 5V, 2

Best regards,

1 Like

Thank you for fast reply!
May the solution be to change the 3.3v pin through voltage booster and connect it to 5v pin?
it should not be too hard , but i have no idea would that harm the board or not…

You will also need to check the IO voltage levels of your 5V sensors, as they are likely 5V as well.

The IO pins can only operate at 3.3V levels and you will cause damage to the micro-controller if you apply higher voltages (such as sensor with 5V logic levels). For a sensor with 5V levels you will also need to add a level-shifter to convert the signals between 3.3V and 5V.

maybe there is a command for controller to expect 5V signals?
because when USB power is in and 5V pin working , everything is OK!

Also any suggestions how to use Step up converter?
possibility’s i see:

  1. Connect via converter 3.3v pin to sensor
  2. Connect via converter 3.3v pin to 5v pin
    3.(crazy idea) 3.3v pin connect via converter to USB (if it enables 5V levels to work)
    (unfortunately , it will try to charge it self?)

No, the SAMD21 is supplied with 3.3V. The absolute maximum rating for the IO pins is VDD +0.6V, or in this case 3.9V. (p. 983

The 5V from the USB is only used to supply the 5V pin, the battery charger and the 3.3V regulator.
Do not attach any sensor which will output more than 3.3V to an IO pin.

You can use something like this for converting the levels:

Got it!
ive ordered both , will need a week for delivery to make a live tests.
will get back to you.

not sure about output voltage, because i connect all sensors via 1 wire technology using 4.7Kom resistance.
As it was not damaged this far, would need one more test i think.