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basic lipo circuit

cpeachock

Jul 17, 2014
2
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Jul 17, 2014
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Hello I am trying to use one battery circuit to power 2 different voltages.

One device needs 3.7 Volts the other requires 7.4 voltage.
Also there needs to be a recharging point (obviously)


Attached is a crude schematic of the idea in mind. Any feedback is appreciated :)
 

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(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
Moderator
Jan 21, 2010
25,510
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25,510
You want points A and D to give you 7.4V, and B and C to give you 3.7V.

One obvious problem is that A is connected to B and D is connected to C. This means the potential between A and D will be the same as that between B and C.

Simply put, you are trying to connect the batteries in series and in parallel ar the same time. You can't do that.

In this case, you will have effectively shorted out the lower battery through point C and the upper diode (which is what I assume the triangles are)
 

cpeachock

Jul 17, 2014
2
Joined
Jul 17, 2014
Messages
2
Thanks for the info Steve just the insight I was looking for.
I might go another route then.

Can I use a 7.4 series and have it branch off to 2 different voltage outputs 7.4 and 5 volts? I am guessing I could use resistors on one of the branches to step down the output for the lower 5volt device?

Let me know what you think. Thanks so much for the help :)
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
Moderator
Jan 21, 2010
25,510
Joined
Jan 21, 2010
Messages
25,510
You can power a 5V regulator from the 7.4V rail and that will create a 5V output. The batteries are likely to be as low as 2.8V when flat, so the minimum input voltage will be 5.6V. You will need a low dropout regulator as normal regulators require as much as 2V more than their output.
 
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