Board does not work when powered by coin cell battery

[bluetooth_mdw]

My nRF52 DK has PCA10040 V1.1.0 2016.34 682272915 on a label.

It works fine when connected to my laptop over USB. If I try to power it from the coin battery underneath though, there's no sign of life. The LED does not light and I can no longer detect its Bluetooth advertising. I have to conclude it has not powered up. I've checked the battery with a multimeter and it's showing 2.78V. I've tried another battery.

Do I need to change a jumper or something? I couldn't find any information that suggests using a battery to provide power requires any kind of special action.

Thanks

Martin

[bjorn-spockeli]

Hi Martin,

I assume that the nRF52 DK has been flashed with one of the SDK examples and that it is working if you power it through the USB connector?

Could you measure the DEC1-3 voltages to verify that the internal regulators are working as they should.

DEC1 is connected to ground through C4, you should see about ~1.0 V

DEC2 is connected to ground through C6, you should see about ~1.2 V
(unpopulated so just measure the pad on the nRF Side). 

DEC3 is connected to ground through C7, you should see the same voltage as at SB11 (VBAT - the forward voltage of the protection diode)

Best regards

Bjørn

[bluetooth_mdw]

Hi

With battery inserted and no usb connection:

C4 = 1.0

C6 = 1.25

C7 = 2.25

Regards

Martin

[cbd]

From what Bjorn said C7 voltage looks a little low, what does it read when the USB is connected?

[bluetooth_mdw]

Not sure. Really difficult to measure...seems to jump around but probably I'm doing it wrong! Hardware is not my thing :-)

[bluetooth_mdw]

This morning, it's working fine. No LED lit but advertising plainly happening. I have no idea why. It definitely wasn't advertising yesterday (using nRF Connect to check). I'll keep an eye on this but close in the meantime.

[cbd]

you'll see that if the Bluetooth is enabled. Each data burst draws current from the battery in doing so you'll see the voltage dip. As the battery depletes it becomes worse.

you'll often see batteries recover slightly if left for s while.