Solar Charger using Low drop Regulator. Design Trick 6

Using a positive voltage regulator IC, it is easy to make a simple voltage controlled charger in solar powered devices. LM 2941 CT is the low drop positive voltage regulator with the capability of 1 Amps current output. Unlike other regulator ICs, LM2941 shows a typical voltage dropout of 500mV to 1 V in all temperature conditions. Another important feature of the IC is that a current reduction circuit is included to reduce the ground pin current when the differential between the input and output voltage exceeds 3 volts. When the input voltage exceeds the maximum rating of the IC due to transients, the IC automatically shutdown to protect both its internal circuit and the load. It also has short circuit and thermal overload protection. IC 2941 is the 5 pin IC with an Adjust pin and On/Off pin in addition to input, output and ground pins. A 12 volt 10 watts Solar panel gives around 20 volts and 1.2 Amps current in bright sunlight. To prevent excess voltage entering into the battery, this voltage adjustable charger  can be used.

Adjust VR to get the desired voltage to charge 12 volt Lead Acid or tubular battery. The voltage should be 15 volts for charging the battery.


7 responses to “Solar Charger using Low drop Regulator. Design Trick 6

  1. its nice,
    Dear sir,

    Is There any circuit design can made to charge 9V 7.5AH battery with 12V near about 800mA current provide by solar panel ??

    • Dear Deepak
      A 12 V Solar panel generates about 20 volts DC in bright sunlight.If a charger controller is not required, connect IN4007 diode in series with the + line from panel and a 470uF 25 V capacitor across + and – lines. The cathode of the diode should go to the + terminal of the battery.Current from the panel depends on voltage and a 10 Watt panel gives maximum 1.2 Amps in full light. You can use a 12 volt 10W panel to charge 9 volt battery.

  2. IC 2941 CT is not available in the shops at Eranakulam. pl inform the availability of the same or the substitute …

  3. nice work.
    Optocoupler (NB need photodiode output) can make decent current controlled current source which can go down into the uA amp range. most regulator ICs will usually struggle below mA
    at bottom
    Would be interesting to know if larger power solar cells will output higher constant current.