I have been reading stackexchange for last 5 days but could not see any proper / answered circuit / discussion about Lipo battery charging and backup and thus asking the question here.

I am doing a circuit (GSM Modem Based) which eats around 50mA current for normal operation and a peak current of 1.6A (While GSM bursts).

I need a backup solution for the device. The circuit runs on 4V (Actually the GSM Modem can work within a voltage range of 3.6V to 4.4V. I am thinking to put a 700mAh Lipo as the power backup.

Now for the main power regulator of my circuit I have chosen LM2596 and for Lipo Charger I have made my mind to use TP4056 (for its damn low price). I know that there are specially designed power path management ICs from Texas Instruments, Microchips and other vendors, but they are costly. This circuit is a LOW COST challenge.

Can anyone guide me for a circuit for battery charging and power source switching?

  • \$\begingroup\$ What cost target did you have in mind for : charger, 1 cell battery protection , with a 3A switched output? I can get for ~$2/board with USB port but accepts 4.5~8Vin. with solder or screw lug pads for in/out. That is pretty LOW COST, wouldn't you say? If not what is? \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Apr 6 '18 at 6:38
  • \$\begingroup\$ How damn low is the price of the TP4056? The BQ2407x looks also cheap and does charging and power path management. \$\endgroup\$ – Arsenal Apr 6 '18 at 7:02
  • \$\begingroup\$ I checked BQ2407x, but it costs a lot, around 2 USD, and then I need another regulator before it, as the main DC input can go upto 30V (to be on safe side, I need to be compatible upto 40V), but BQ2407 doex not accept that range. TP4056 is just 20 cents. I need one 8205A (Dual channel mosfet) as over charge, over discharge protection. That is also like 20 cents.. \$\endgroup\$ – Rakesh Mehta Apr 6 '18 at 7:13
  • \$\begingroup\$ I Tony, do you have the schematic of that board? I can connect another regulator before it to accept higher voltage range. If you can direct me to the schematic, that would be great. \$\endgroup\$ – Rakesh Mehta Apr 6 '18 at 7:14

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