Basically, for the circuit I'm making, I need it to be powered by a Lithium battery. Also, this Lithium battery has to be able to be charged via USB.

I have seen external chargers for doing so, however, these would require for me to take the battery out each time and then re-charge it.

I have found this product, on sparkfun: Sparkfun

And the circuit/useage schematic looks like:

enter image description here

So if I understand this correctly:

Pin 1: USB (Power Lead) Pin 2: USB (GND)

Pin 5: BAT (Power Lead)

The question is this: Suppose this is charging the battery, how can I therefore power the circuit? Since, I'm guessing that both of the leads from the Lithium battery go into the charger, rather than the circuit or the PIC?

  • \$\begingroup\$ Where did you get the concept or term "RATHER" from? | There is NO rather. The words you want are eg SIMULTANEOUSLY, both at once, together, at the same time, connected together, ... \$\endgroup\$ – Russell McMahon Jan 27 '15 at 13:32

You MUST look at the diagrams in the data sheet and understand what they show.

You must read the answers that people give and actually take note of what they say.
apalopohapa have you a completely clear answer.
You ignored what he said and just asked the question again.

He said "The battery goes both to the charger and the circuit."

This means

  • The battery goes to the charger


  • the battery at the same time goes to the circuit.

If you read a sentence like that and it makes no sense then read it again (and again and again) - maybe draw a diagram - or simply look at the diagram in the datasheet.
It shows the output going to the battery
AND AT THE SAME TIME to the system load.

And apalopohapa also said "When you are charging the battery, you are still powering the circuit."

This means

  • When you are charging the battery

  • you are still powering the circuit.

If that does not make sense then reread, rereread, rererereread.

Look at this diagram.
The charger IC output is connected to the battery
The charger IC output is connected to the load.
It connects to the load and battery at the same time.
It connects to the battery and the load at the same time.
All 3 are connected together at once.
Does that make sense?

enter image description here

  • \$\begingroup\$ Thank you for the reply (However blunt it was). This makes sense now. I'm going to put it into practice but this model now makes sense. \$\endgroup\$ – Phorce Jan 27 '15 at 14:45
  • 2
    \$\begingroup\$ @Phorce Sorry for 'bluntness' but it seemed you were somewhat stuck in a loop and needed some non-maskable interrupt action :-). I'm glad you are now on track. More questions, please ask. \$\endgroup\$ – Russell McMahon Jan 27 '15 at 23:18

The battery goes both to the charger and the circuit. When you are charging the battery, you are still powering the circuit. To turn the device off, you would normally have to either provide a switch (mechanical or solid state) that disconnects the battery from the rest of the circuit , or have the circuit go into a low power mode that won't drain the battery in a reasonable time.

  • \$\begingroup\$ Thanks for the reply. What therefore goes into "DC" and I'm a bit confused. How do I connect the battery to the circuit as well as the charger? \$\endgroup\$ – Phorce Jan 27 '15 at 11:14
  • \$\begingroup\$ @Phorce DC is just another charging input with wider input voltage range and potentially higher max current. The USB input is special because it limits the current to 100 mA, per USB spec. \$\endgroup\$ – apalopohapa Jan 27 '15 at 11:33
  • \$\begingroup\$ Thanks! At the weekend, I'm going to be making this circuit on a breadboard - So I'm going to start with the power before I move onto more complex stuff :) Thanks for your help. I just don't understand how it powers the board up? \$\endgroup\$ – Phorce Jan 27 '15 at 11:35

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