External/Battery switch

[zejulios]

Hello,

I have a new project that I need to work with external supply and battery when external supply is not used.
I'm thinking of a 5V external adapter, that will charge a 3,7V Lion battery, and my circuit should run at 3V3.
I need to detect when my system is on battery, and also charge the battery when external power is connected.

I have several solutions, but would like to hear more options for:

- change from external/battery on the fly
- shutdown if battery is too low
- charge the battery when connected to external

I'm also looking for a small battery, like the cell phone battery, with cables, where can I find them with more than 1Ah?
I'm from europe.

Thanks,

ZJ

 

[kam1787]

there are many li-ion battery charger circuits available [Google is your friend!] - many use a custom IC at the heart, however few provide a 'safe' way of recharging and powering a circuit.

It might be better to detect when the external power supply is active, rather than when on battery - less current drain on the battery.

on your second item [shutdown if battery is too low] - what is the load? I think that will happen anyhow...........however, it requires another [different] circuit.

 

[thylacine1975]

Aye, I've used Microchip's MCP73831 (**broken link removed**) on many occasions to solve the external power/LiIon battery charger/handover problem for nearly zero space and $$s.

The controlling micro can then be powered full time from the battery, and the charging/power status read via the MCP73831 status flag and a second GPIO sensing the presence of a +5V charging supply.

 

[zejulios]

Hello,

Thanks for your replays, I was expecting some part numbers, like thylacine1975.
I did not mention what parts did I choose so anyone can point me others, or to know if I'm on right path.
The microchip thylacine told was exacly what I'm thinking of, so maybe I'm on right track .

Thanks!

 

[zejulios]

There are some devices from linear that does all of this.
Has anyone used them?
Any alternatives?