Asset Tracker V2 power consumption with Thingy:91

[Hidastelija]

I'm learning to use the Asset Tracker V2 example and planning to build a POC product on top the example. The biggest issue at the moment is with power consumption. On the Nordic web pages there are a lot of information on power consumption of different parts of nRF9160 SOC, but I haven't found any real numbers from an actual use case using Thingy:91 HW.

I'm running the following setup:
- Thingy:91, with nRF9160 V1 SOC, modem FW 1.3.0
- Asset Tracker V2 example from nRF Connect SDK 1.6.0
- modified SW to use eDRX with default value ("1001" / 163sek)
- using SUPL for AGPS
- configuration is "Normal" + CONFIG_LED_CONTROL=n copied from low_power_conf
- Device is connected to my own AWS deployment of "Cat Tracker" example
- Device parameters from Cat Tracker: Passive mode, movement res 120sek, movement timeout 3600 sek, GPS timeout 29sek

The modem is configured to use eDRX, because in my earlier test the Thingy logs with default SW requesting PSM got a response -1 from network (DNA / Finland). I assumed the response says no PSM.

My test setup has been running on battery for almost two weeks now and the battery level is currenly at 3.75V. On the first few days the Thingy was actually moving for about an hour per day. The rest of the days it has been standing still inside without GPS signal. I'm expecting that the battery won't last much more than two weeks with this setup.

Questions:
How long one should expect the Thingy can run on battery using default Asset Tracker V2 parameters?
What are the most power hungry parts in the application --> where to start optimizing?
Is the nRF52 part on the Thingy:91 using any power? I have not updated/changed the SW on the nRF52.

[Hidastelija]

Hi Övind and thank you for the reply,

The thread on Thingy:91 Power consumption is interesting, but it is kind of at the other end than I am at the moment. Right now I'm not trying to get the absolutely lowest possible power consumption. I'd be happy with around 0,4mA avg current (about 4 months battery life) with SW that is as close as possible to the Asset Tracker V2 example.

The asset tracker V2 example is very nice and implements most of the requirements for the prototype that I need to create. One of the major and to me most difficult tasks is to get the power consumption low enough for the Thingy battery to last some months.

According to the modem specs, the difference in avg current between PSM and eDRX is 30uA or less. The actual figure naturally depends on the timer for each mode. To get the modem to reasonably low power mode, I changed the code in Asset Tracker V2 example to request eDRX instead of PSM.

I think the Asset Tracker V2 only tries to get PSM, not eDRX at all. I did this change, because lte_evt_handler / "case LTE_LC_EVT_PSM_UPDATE" in modem_module.c prints -1 for TAU. After changing to eDRX the debug print in "case LTE_LC_EVT_EDRX_UPDATE" looks ok to me. I just got a new SIM card to TELIA network. I will test this next with the original PSM config.

Can you tell me: Given favorable network conditions/parameters, can Thingy:91 with the Asset Tracker V2 SW be expected to run months on battery when built with low_power_conf?

Kind Regards,

Ilkka

[Øyvind]

Hello Ilkka,

I've talked to our Thingy:91 designers, and they say that with v1.6 of the Thingy:91 you should be able to achieve up to 6 months of theoretical battery life. With the Asset Tracker v2 low power config it draws just under 40 µA at 3.7V in PSM, and removing the accelerometer part gets it down to 10-15µA in PSM.

Thingy:91 versions prior to v1.6 are not able to achieve lower than 200µA due to the RF switches. On v1.6 these are turned on only when needed, controlled by one of the COEX pins in the modem.

The battery life is, as mentioned, affected by GPS fix time, and bad reception depending on how much the device needs to search for the network..

Kind regards,
Øyvind

 

[Hidastelija]

We did some more testing and got some info. Apparently DNA network didn't like the default PSM parameters in  Asset_tracker_v2 example. The default parameters are too long sleep time and too short active time. As a result the network didn't accept PSM.

However, when using Telia sim card, current consumption was as low as 400uA avg with 8min data update interval. This is great!

Configuration:
- Thingy:91 (1.4.0 & MFW 1.3.0)
- Asset_tracker_v2 (low_power_conf + GPS disabled)

Using LTE Link Monitor I was able to test different network parameters with AT+CPSMS to find a configuration that works for DNA network.

Ilkka 

[Øyvind]

Ilkka, very happy to hear about that result! 

In the DNA network, did you try to change the default PSM parameters? Do you know if PSM is possible, and if so, what settings should possible?

-Øyvind