SIM800L Module

Projects Networking, Protocols, and Devices
1

Hi All

I have one of these SIM800 modules and want to power it from a LiPo battery rather than 5v source. If I connect 5v it works as expected, but if I connect a LiPo I get 6-9 flashes of the NET LED indicating unregistered then the RING and NET LEDs go off for a second then the process repeats - as if it's not getting enough power at its peak time when connecting to the network.

Almost all of the listings I can find for this module online (Amazon, Ali Express, eBay) all list it as 3.7 - 5v input range. I have tried using the 5v and also the VDD pin to connect the LiPo and have also tried using an external 470uF cap too. I have also connected both GNDs.

Multi meter reports 4.14v from the LiPo.

Has anybody actually had these working from a LiPo before?

1600×1600 295 KB

Thanks

Nick

2

Ok so it looks like the two diodes D1 and D3 in series regulate the voltage in a linear fashion. Connecting a LiPo to the 5v pin results in just over 3v at the output of D1 which then supplies the SIM800.

VCC appears to be a bias line level shifting for the UART buses and not any kind of power input for the module.

I'm guessing nobody has powered these from a LiPo directly and it's just poor copy and paste marketing where these are listed online as having a large voltage range.

Looks like options are remove D1 and D3 and replace with shorts or to use a 2A boost converter to get 5v from the LiPo before the module.

Nick