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Hello,

So I've been wondering this for a long time and I figure I should ask. 

Say I have a circuit that runs off a rechargeable battery.  How would I make a circuit so that I don't have to unplug the battery and be able to recharge it?
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Use a chip like MAX1811, charges a LiPo battery when 5V is available, runs from the battery when 5V is not available.
Spartfun carries several charge control boards with a similar part.
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MMkay, so If I have 2 LiPo batteries supplying 7.4v, and then a re-charger that recharges it when there are 5v available? 
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No, you need a different chip for that, one that can boost the 5V to something higher to charge the LiPo's.

Either that or charge the battery from 5V, and then boost the battery 4.2V to 3.7V output to 5V for your circuit.

I think sparkfun has a board that does that.
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Designing & building electrical circuits for over 25 years. Check out the ATMega1284P based Bobuino and other '328P & '1284P creations & offerings at  www.crossroadsfencing.com/BobuinoRev17.
Arduino for Teens available at Amazon.com.

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Alright thanks alot crossroads!
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