I am designing my first Li-ion charging circuit, based on the Adafruit Powerboost 1000C, and this is what I have so far:

Charging circuit draft 1

I am probably going to also add a way to read the battery voltage based on this post, but that's not what this question concerns. The circuit uses the MCP73871 to manage charging and load sharing, the BD4933G 3.3V voltage supervisor to turn off the load when the battery voltage is <3.3V, and the TPS61090 boost converter to boost the battery voltage to 5V (5.2 to allow fluctuations and drop), and also provide a status output when the battery drops below <3.45V.

I am wanting to know where the best place to put a master switch would be - would it simply be connected directly in series with the battery? Does it matter if its the +ve or -ve battery terminal? Is there a better place to put it?

Thanks in advance for your help

  • \$\begingroup\$ Where to connect it depends on why [if at all] you need it. What's the purpose of master switch? Is it for numan use? Is it a circuit breaker under internal conrtrol? Both? It would also be nice to know the purpose of your device. \$\endgroup\$ – Nick Alexeev Jun 7 '18 at 21:35
  • \$\begingroup\$ Hi @NickAlexeev , the idea for the switch was for human use, just to make sure that when the system isn't in use it can be properly turned off, and that there isn't any current being drawn. I'm leaning towards having the switch simply in series with the battery, but wanted to make sure that there are no disadvantages to this. The device is an LPC1768 microcontroller on an mbed development board and a number of sensors recording data to be logged. \$\endgroup\$ – rno Jun 8 '18 at 18:52

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