Cant figure it out..

** the battery that I used below is somewhat like from motorctyce battery so i choose not to place an overcharging circuit.

** I want to use the solar panel ONLY for charging the battery but it wont supply my arduino. Only the battery must supply power to the microcontroller. HOW can I make a buffer from the solar panel to the arduino? TIA.

** I got an idea but i dunno if it will work, Ill be placing a resistor between the positive side of battery and positive side of my arduino. will the current from the panel flow only to the battery???



thanks felas!

As you drew it, but the regulator needs to be a shunt regulator set to a peak voltage of 6.9V. If the lead-acid battery goes any higher than 6.9V it will be damaged. The battery voltage will sag to ~5.7V if it becomes almost totally discharged (when there is no sun). The built-in regulator in the Arduino can handle 5.7 to 6.9V. You should not allow the battery voltage to get below 5.7V without disconnecting the Arduino and other loads, that will damage it, too.

I suggest you start by reading this link. There is more to doing what you want to do than a block diagram. The link is a good start.

<EDIT> Wow, I see Mike is up and about. </EDIT>

Ron

Thats a great link Ron, pretty much answers his questions. I doubt there's a way to stop the solar panel both charging and supplying the arduino, and I dont see why you need to worry about that anyway? As long as your solar panel is powerful enough to fully charge the battery and power the arduino during the day, and then your battery large enough to power your circuit at night and not discharge itself too low. For that work out your required AH battery rating.

Then as an added protection, its very simple to create a load cut circuit to protect your battery from discharging too much during battery backup. For example, you can either get a voltage monitor chip and use it to trigger a high side p-mosfet, or use a simple opamp to trigger for the mosfet, or something along those lines. I'd go the voltage monitor and p-fet route, dead simple.