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Old 01-08-08, 12:01 PM
  #22  
n4zou
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Originally Posted by Platy
Okay, I now have some practical experience with my zener regulated USB charger. The bottom line is that n4zou's design is simpler and more efficient. I was unable to pick a single fixed zener voltage that would efficiently charge the batteries and at the same time prevent overcharging.

That is, if you select a zener voltage that's high enough to allow efficient battery charging, it won't be low enough to prevent overcharging. Therefore, it really accomplished nothing of benefit to have a zener regulator at all, since the batteries do a very fine job of regulating (up to the point where they are overcharged).
I thought about including some sort of battery charging circuit to control charging but fell back to the KISS design Keeping It Simple. Less stuff to buy and less stuff to go bad later. I used solder tab batteries as having a bad connection would cause a loss of voltage and current regulation. This would not harm the LED's very much but pushing too much current and voltage into my Palm TIX and Bluetooth GPS receiver would be a disaster. Using standard rechargeable batteries in a modified battery charger is fine as long as your not depending on them for voltage and current regulation. If you lose your connection across the contact points between the batteries all that happens is you stop recharging them.
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