Hello All,

I'm making GSM alarm controller using a SIM800L GSM chip from SIMCOM.

Since the project is about "monitoring" and "alarming", it is important ton ensure a redundant power feeding (= LiPo battery).

The module supports 3.4 to 4.4 VDC and I would imagine to go for 4VDC (my imagination - will depend on circuit design). For info, this chip draws up to 2 Amps when bursts occur (!) but draws around 40mA in idle state.

I've read some threats about "oring" DC power sources (with Schottky diodes or so) but here I don't know how to achieve a correct circuit since I'll be using a rechargeable battery (not like a battery for an RTC).

My points are:
- is the schema here under or something looking like "possible" at all?
- the LiPo 3.7V cell will need to be charged (or not!) after a +/- long main voltage supply (i.e. 12VDC) supply but how is it possible since it is connected in parallel with another circuit
- if there is already something "out there", can anyone point me to a link please?

Thanks for any info

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