No problem, it looks like I had my logic backwards (which is the norm for me), thinking A6 was high before seeing the code. Made up a little key pad so will have to add the diodes/resistors and give it a go, looks good!

Using the 8Mhz internal oscillator the best PWM resolution is only 8 bits. So at best with a 5V reference you have 0.02V steps. Multiply that by the divider of four for a final 0.1V resolution. Is that good enough? Using an external oscillator, or an 18f with HSPLL , you could get that to ten bits I think, or 0.02V final resolution.

More bloat to add?, red led- bulk charge, orange led- absorb charge, green led- float charge, and led for dump load.

EDIT: This is going to be a buck converter for me, as the open circuit voltage is around 21V for the so called 12V panel.

 

I posted reply in the new thread Pommie made. I really don't think it's worth trying to do SMPS MPPT on a 12v to 12v system. The power gains are too small for that much complexity and reliability.

 

The MPPT part was going to be the last thing on my list. Would be interesting to fiddle with, if only for the educational part. Have most all the parts I think.

Going to follow the PicDem Buck Development board schematic, and try out a tc4426 inverting mosfet driver and a irfr5023 p-channel mosfet for the voltage control mode next.

Any, and all insights, much appreciated.

 

Hi
I need a help to design a battery charger from solar panel , I have a 6V 2.2W solar panel which I am connecting to a 3.6V NIMH 2500mAh battery, I want to use a MOSFET as switch so I will be monitoring the bat voltage , when rich 4.5V the MOSFET will be turned OFF , the reason also that I am using the MOSFET is to not have too much losses and also for power of thr battery not to come back to the solar once the MOSFET is OFF and solar voltage is lower than the Battery.

 

Hi,

I am working on a MPPT charger for 12V panels using a PICmicro.

The panel is connected to a variable buck converter and then to a battery. The PICmicro monitors the PV, PI, BV and BI. The buck converter reference is varied based on the power input and output calculations to achieve MPPT.

I have the PCB ready and am yet to develop the software for this. Hope this idea works out.

Cheers

Ravi

 

Ok I've finished a version of a PIC 12F675 based solar battery charge controller. All the source code is open source in Mikro C compiler. It's using a little PCB I created that all mounts on the back of the 16x2 LCD.

It's fairly sophisticated in that it can be set to display battery voltage 6v 12v 24v 36v 48v etc and the setpoint voltage (where charging cuts out) can be adjusted in 0.02v steps (with a 12v system) and the settings all save to eeprom so they remain when next powered up.

It's a bit crude in that it only has the most basic of features to display the battery voltage, setpoint voltage and whether the load is on etc. I couldn't fit too many more features in as the little 1k memory in the 12F675 is pretty much maxed out. So it's got no datalogging or niceties like that.



This is the charge controller mounted on the back of a 16x2 LCD, it uses the little Shift1-LCD PCB I designed;





For this solar charge controller it doesn't need much more than a pot to calibrate the battery voltage, 2 buttons, and a transistor and relay to turn the Load on/off.

More info and schematic etc can be found on this page (all code and design is open source);
Shift1-LCD Projects

And Bryan1, I'm quite happy to send you a free assembled PCB with the PIC and charge controller firmware already installed. In return I'd just like a photo of how you used it to put up on my web page. I don't have any spare text LCDs at the moment (for some reason i have gone through a lot lately ) so you need to supply your own 16x2 LCD.

 

I'm new to this site.
This is awesome.
Just what I've been looking for.
I have some parts and wanted to build an MPPT for wind and hydro with a DC KWH meter since it will use the same pic controller.
Amps will be up to almost 200 with wind so I would rather use a shunt as opposed to a hall sensor.
I'll reread this post to absorb more and keep in touch.

Thanx