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Here's a simple possibility (not optimised for maximum energy extraction from the panel):-
View attachment 74024
...I don't have to concern about the current as far as i'm using the solar panel...
Posts #1 and #9
Thanks Eric. Duly downloaded.
You do not need to worry about protecting the battery from excessive charge rate early in the charge cycle.
YesHi MikeMl
1. I have to make a 7.2V power supply (with solar panel).
Yes2. A current sensor for measuring the current which goes through from 7.2V V. Reg to battery.
swift=switch3. At the time of sensing less than or equal to 20mA current the circuit should be able to swift 7.2V regulator to 6.8V
4. and finally cut off the battery after full charging....
but I can't download the zip file!!!!!!! (may be this is not for me!!!!!!).
hi ike,
I have just done a test download of the zip, it all ok here.?
E
...can any one help me in the circuit for the sensing of 20mA current......????
Was in the earlier referenced forum thread.
In that case will a fixed shunt regulator at 6.8V allow rapid-enough charging to maintain the battery at full charge? I think something more elaborate is called for. Perhaps a 7V reg which shuts off, or reduces the regulated volts, once the charge current has dropped down to 20-30mA, then turns on/reverts to 7V again when the battery voltage has dropped down to 5.5V or so?it'll be used for emergency light..... all most every day.........
It's really hard to say, but here is my thinking... The panel can only put out 3 watts at high noon on a sunny day so it won't be able to charge a dead battery in one day no matter what we do. By the time you add something like a 317 and a diode to keep the battery from flowing backwards into the panel almost 30% of the power would be lost to heat not to mention the dropout voltage that would have the effect of shortening the charge time. I guess we could build a MPP charge controller and do a little better or maybe a buck boost with some battery management, but is it worth the complexity and expense?In that case will a fixed shunt regulator at 6.8V allow rapid-enough charging to maintain the battery at full charge? I think something more elaborate is called for. Perhaps a 7V reg which shuts off, or reduces the regulated volts, once the charge current has dropped down to 20-30mA, then turns on/reverts to 7V again when the battery voltage has dropped down to 5.5V or so?
The simple circuit would get the battery back to about 80% about as fast as anything and for less money
I'll go along with that thinking. With a 6.8V shunt should we be able to leave the charger