I'm trying to build a battery backup system for a door lock. I'm using the LTC4353 voltage monitor and switch that switches between the battery and a regulated DC supply depending on the AC mains availability.

Now I also need to charge the Li-Po pack and I was hoping someone could suggest me a suitable IC for this? The battery backup is 4, 18650 batteries in series (with a total voltage of 14.8 volts and current of about 2200mAh). I did a bit of research and found so many that I'm totally confused. The main criteria for the charger are,

  1. Should be able to stop charging after they are fully charged
  2. Should be capable of a trickle charge
  3. Low cost and low part count
  4. High charge efficiency

You can do everything you're looking to do with a single device. YOu're looking for a feature called Power path that will do two things:

1) Charge the battery independantly from power the system 2) When charger input isn't connected, powers the system from the charger

For your issues:

  1. Detection of charge finalized depends on setting the taper current. Typically this is 10% of the max current during full charge
  2. Same as above. Charge continues until about 10% of full charging current

This list should get you started.

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