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andersskogen asked

GSM modem goes offline


I have an issue similiar to GSM modem offline 3.

We are running 8 off-grid systems (Multiplus + Cerbo GX) in Malawi, with more coming. Comms is through the Victron 4G GSM dongle using Airtel (mostly) or TNM sims. On commissioning, all systems were online. However, during the first couple of days, five systems dropped (and remained) offline while three have remained online.

The "worst" example dropped offline 12 days ago, never to reappear. None of the systems that have been more than a few minutes offline have recovered. At the same time, we have other GSM based equipment onsite that has remained online. Some sites are clearly far off grid, but weak signal locations have extra antennas. Connection drop does not seem to only his weak connection sites. It takes between an hour and a day to reach these sites from the capital, hence we need to go prepared.

We have been to the first (closest) site to assess. Site has good Airtel coverage, but we first tried TNM, and the GSM/Cerbo produced error 153 (Routing error). With an Airtel sim it complained about APN for a few minutes before going online with good reception. (3 bars), allowing remote VRM login. After leaving the site, the connection dropped within an hour, never to recover.

Relevant settings:

- Cerbo GX Firmware version v2.70~5-large-18

- APN: set to “Use Default”. Required APN is “internet” for both Malawi carriers. Since we had access, I do not consider this the root cause, but we are happy to change this. We have set this to "internet" for one of the working connections, this works too.

- Settings->VRM-> «Reboot device on no contact with VRM» was not enabled at first. We have instructed that new installations should enable this feature. However, this is in my opinion a way around the problem rather than a real repair.

- FW update set to "Check only" to avoid uncontrolled updates and data use.

- Roaming is off. Will enabling this give us greater chances of remaining online?

Is there anything Victron or us can do here? Could there be a specific airtel/TNM Malawi<-->Victron issue that prevents the cerbo to reconnect if connection drops? Any advice would be good before we start driving around the country.

cerbo gxoffgridgsm
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