| ChadMan wrote:
| > | >
| > 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<---o---(-)
| > Batt (-) |
| > o------------------'
| > (created by AACircuit v1.28.6 beta 04/19/05
www.tech-chat.de)
| >
| >
|
| 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.