Solar Charger for 6V Battery

[lilgirl]

Hi! I would like to design a solar charger for my 6V AAA battery ( 4 AAA batteries connected in series). Can anyone share any safe and efficient circuit designs? I understand that I will need a solar panel that is higher than 6V. In that case, is a 7V or 9V solar panel sufficient?

Also, how do I protect the battery from over-charging?

Thanks so much! Looking forward to replies!

 

[techie]

Solar panels dont give a fixed voltage output. A typical panel for your use will have an open circuit voltage of 21volts and short circuit current of 700mA or so when exposed to direct sunlight. You can use a 10W panel to do this but you will need some charge regulation as well so that the batteries dont get overcharged.

 

[Dmitron]

typical IC - MC34063.
you can make a step up-step down circuit, and battary will charging if input voltage below or higher then the battarie voltage. But it willn't give you much current.
for step down circuit use MC34063, For step-up - MC34063 or ZXSC300.
Charging method - constant current - constant voltage (stand - by mode).

 

[praveen sinha]

u can try charge controller using 555 timer it is most simple and cheaper circuit...

 

[eem2am]

You do current mode charger with current sense resistor.....into amplifier, then error amplifier....so you regulate current.

You also sense voltage with comparator, so it stop charging when you reach certain voltage.