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I have one of these charging this battery but it's taking forever. Is the below diagram a good idea or is it dangerous/a better way.

(also please feel free to criticize my diagram. I am trying to learn this on my own and could use the help)

enter image description here

The Charger Specs

https://www.sparkfun.com/products/10401

enter image description here

The Battery Specs

http://www.ebay.com/itm/New-Internal-Battery-replacement-dajn-fit-for-iPad-1st-gen-/231044587897

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  • \$\begingroup\$ That 24.8Whr battery needs a lot of juice to fill it. Perhaps a dedicated mains powered charger may be more suitable. \$\endgroup\$ – JIm Dearden Sep 1 '13 at 16:01
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500mA is not enough to charge that battery in a timely manner (24.8Wh/(0.5A*4V)=12.4h), and that's if you have it connected to a device that it can negotiate with. Consider putting together a current-limited switching regulator with a power MOSFET that can push at least a couple of amperes to the battery (or, you know, just buying one).

But don't put multiple chargers in parallel since even small differences in output voltage could cause damage to either or both chargers.

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  • \$\begingroup\$ I thought that running things in parallel keeps the voltage the same but increases current? \$\endgroup\$ – Anthony Russell Sep 1 '13 at 16:25
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    \$\begingroup\$ It tries to keep the voltage the same. This can involve electricity flowing from the higher voltage source to the lower voltage source. Even if the lower voltage source can't withstand it. \$\endgroup\$ – Ignacio Vazquez-Abrams Sep 1 '13 at 16:26
  • \$\begingroup\$ -1 No, a simple current regulator is an EXTREMELY UNSAFE way to charge a lithium battery. \$\endgroup\$ – Chris Stratton Sep 1 '13 at 17:40
  • \$\begingroup\$ I never said a "current regulator". Obviously you need a fixed-voltage regulator (of the appropriate voltage) that can provide 0.1-2C. \$\endgroup\$ – Ignacio Vazquez-Abrams Sep 1 '13 at 19:00

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