RAK4630 + Li-SOCl2 battery?

Hello everyone :wave:

I am going to start a LoRaWAN node project using a RAK module base along with the Arduino IDE for module programming. I was looking for a module that offers both LoRaWAN connectivity for transmitting sensor data and Bluetooth Low Energy for easily programming my future LoRaWAN node (wakeup time, setting LoRaWAN keys, and so on…). So, I bought the RAK4631 module along with a RAK19007 to easily familiarize myself with the module, which I have (sort of!) done. Now, I would like to power a RAK4630 bare module with a Li-SOCl2 3.6V battery and achieve the best possible battery life. Could you please point me in the right direction, provide datasheets, forum discussions, or any resources to help me get started properly? I haven’t found much information on powering the RAK4630 bare module with a Li-SOCl2 battery, but the datasheet indicates a possible power supply range between 2V and 3.6V, so I assume it’s feasible; I must have overlooked something! Thank you all :slightly_smiling_face:

Welcome to the forum @Nepetalactone

(1) A LiSoCl2 battery cannot deal with the sudden current increase when the device is starting to transmit packets over LoRa/LoRaWAN. You need a super-cap to deal with that current increase.

(2) You can try to supply directly from the battery, but in the two devices we have that are optionally powered from LiSoCl2 batteries, we are using this supply schematic to get a stabilized 3.3V supply:

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Hi @beegee and thank you for welcoming me

A couple of years ago I designed a project using a beefy LiSOCL2 D type battery from Saft and a RN2483 from Microchip, didn’t run into any issue despite the current consumption spikes from the LoRaWAN communicating. As you’ve mentioned, good decoupling is important, and I thank you for the protection circuit with the supercap in it as an example.

For the programmable buck/boost converter circuit, I would like to avoid using such a solution as there is loss in the circuit, even if it has around +90% efficiency. Can you recommend some docs, schematics and examples for using the RAK4630 with a LiSOCL battery without using a buck/boost converter ? Is it as easy as connecting VBAT_NRF and VBAT_SX together onto the 3.6V battery, and VDD_NRF and VBAT_IO_SX together ?

Thank you for your time, have a good day :slightly_smiling_face:

There are posts in the forum where we discussed the single supply variations for the RAK4630

Hi @beegee, and thank you for your response.

Unfortunately, even after reading the recommended forum threads, I cannot decide whether or not this RAK4630 can run on a single LiSOCL battery; it’s really not clear to me… It seems like, by design, the module is made to run only on lithium-ion batteries in solar systems. I think I’ll keep looking for a more suitable candidate for my application…

The module is NOT designed for a specific battery type. It is designed to work from a supply voltage that can come from Li-Ion, LiSoCL2 or any other battery if the voltage of that battery is within the specifications.