| > I wanted to ask a similare question. I have a bunch of 7.2 volt 600 MAH bat | > packs. I want to make a charger for them. | >
| > In this fellows case wouldn't it be better to use a Zener regulator so that | > it wouldn't overcharge? | >
| > Does anyone know of a schematic for these 7.2 AA packs? I'm thinking that I | > could use something like this: | >
| >
| > Batt (+) ___ | > o-------o----|___|-----(+) | > | Charge | > | x-former | > '-----z Batt (-) | | > o------------------' | > (created by AACircuit v1.28.6 beta 04/19/05
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| >
| | That will blow up the zener. | | Here's a simple circuit for slow charging a 600 mah | 7.2 volt pack: | | ------- | +12 ------Vin| 7805 |Vout------+ | ------- | | | [R] 91 ohms 1 watt | | | | +--------------+-----> To Batt + | | Gnd-----------------------------------> To Batt - | | The 7805 will need to dissipate about .3 watts. The TO-220 | package does not need a heat sink at that power, but I'd | use a small sink anyway. The circuit will limit the charge | rate to ~ 55 mA, roughly C/10, which is desireable for | a 14 hour charger. Note that Gnd from the 12 volt supply | connects *only* to the negative side of the battery. | | Ed
Your circuit offers only current control using the 7805 Voltage regulator, which will certainly overcharge the batteries if their voltage is not carefully monitored.
I'd follow the advice of another poster who references design specific IC's such as those from Maxim.