Li-ion battery charger and supply to 5v load

Thread Starter

lwj5

Joined May 17, 2010
13
Hello!

I want to make a circuit where by when the 5v dc source is switched on it charges the 4 X 18650 li-ion batteries in parallel. The total internal resistance of the 4 batteries in parallel is 0.025Ohm and the batteries are pcb protected.

And also while at it, it powers my load (a pocket router) rated at 5V, 1A input.

The maximum my 5V source can produce is 2A.

Here's the part where I just could figure out how to make it. How do I make it so that when the 5V source is present. The load (pocket router) is powered by the source and when the 5V source is switched off, it discharges from the batteries.

credits to ifixit for the battery charger circuit from:
http://forum.allaboutcircuits.com/showthread.php?t=35263&page=3

Any help is appreciated! Thanks in advance
 

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Last edited:

evilclem

Joined Dec 20, 2011
118
Diode from each to the load. The higher voltage source will power the load, this should be the 5V supply when it is present.
 

Thread Starter

lwj5

Joined May 17, 2010
13
Yup i understand that the higher voltage source will drive the load.

Now the problem is that because the battery when fully charge will produce more then 5v through the step up circuit. Thus it will drive the load although the 5v dc source is plugged in. This will also cause the battery to never fully charge.
 

Thread Starter

lwj5

Joined May 17, 2010
13
Thanks for the idea! I managed to do a rough edit of the circuit. The values are not on yet.

but this is roughly how it will look like. Any1 care to comment?

This circuit will be hooked up to the step up circuit in my first post
 

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