High current consumption

[Arsenii Maksimov]

We are using nRF9160 and have a rare issue with a very high current consumption from the battery. We are using lithium-thionyl chloride 3,6V batteries, three in parallel.

Here is the picture of one of these events: 400mA pulses of 250ms duration, inbetween 60mA consumption of 35ms.

This event happens very rarely e.g. 1 time per 10 hours but is still repeatable. It begins as a common transmission procedure, where the energy can be delivered from the supercap we are using. But then as it is discharging, energy starts to be delivered from the battery, causing voltage drops down to 3,0V.

The same event could be simulated by challenging the device by dropping RSRP values lower than 20. But during this observation RSRP values are always good >40. We checked also if there is any relationship to BS-change and could not exactly determine that.

Do you have any ideas what can be the reason for that?

Does it look familiar to anybody, maybe not particular values but the shape of curves?

[Håkon Alseth]

Hi,

 

A normal scenario for LTE M1 is 1-3 ms tx period, with a 5 ms gap until the next frame.

In scenarios where you are in coverage enhanced mode (ie. bad RF conditions), you can get into a worst-case of 32 ms TX period (CE Mode A). You can check the CE mode using this AT command: https://infocenter.nordicsemi.com/topic/ref_at_commands/REF/at_commands/mob_termination_ctrl_status/ceinfo_set.html

But then as it is discharging, energy starts to be delivered from the battery, causing voltage drops down to 3,0V.

It is very important that you do not drop under 3.0V, as this will trigger the brown out reset. You can read more about this here:

https://infocenter.nordicsemi.com/topic/nwp_037/WP/nwp_037/vdd1_vdd2.html

 

Do you have any ideas what can be the reason for that?

Does it look familiar to anybody, maybe not particular values but the shape of curves?

Your link quality is bad, so you're (highly likely) seeing re-transmits. A modem trace can confirm this, but based on your RSRP values, your network link is essentially close to disconnecting.

We are using nRF9160 and have a rare issue with a very high current consumption from the battery. We are using lithium-thionyl chloride 3,6V batteries, three in parallel.

Here is the picture of one of these events: 400mA pulses of 250ms duration, inbetween 60mA consumption of 35ms.

As you mention, the curve of the picture is due to the supercap being fully discharged. The batteries does not seem to be capable of providing enough current for this "out-of-range" or "re-transmit" scenario.

What is the maximum current you can draw from your batteries? Please note that the min. required voltage is 3.0V, so they should not dip underneath this voltage.

 

Kind regards,

Håkon

[Arsenii Maksimov]

Hello Håkon,

thank you for the answer.

Our battery is capable of delivering 820 mA current in a short time. These pictures represent a battery voltage, not the voltage supply of modem. Between battery and modem we have a DCDC-boost convertor that is fast enough to deliver a smooth VDD of 3.6V. We also do not see any brown out resets during measurements.

Håkon Alseth said:

In scenarios where you are in coverage enhanced mode (ie. bad RF conditions), you can get into a worst-case of 32 ms TX period (CE Mode A).

Is there any possibility to turn off this feature of CE Mode A?

Best regards

Arsenii

[Håkon Alseth]

Hi,

 

You cannot disable it explicitly, but you can detect it by listening to notifications from this AT command and add your own application logic to handle the scenario:

https://infocenter.nordicsemi.com/topic/ref_at_commands/REF/at_commands/mob_termination_ctrl_status/xsnrsq_set.html?cp=2_1_4_5_0

Kind regards,

Håkon