I am trying to create a PWM signal to charge a 12V AGM lead acid battery from a 100W solar panel. Of course the charge controller has multiple functions depending on the charge of the battery but I am kind of stuck at initially creating the PWM signal itself. Is there a typical method used? I've only ever used a 555 timer to create a pwm signal, but I haven't noticed any 555 timers so far in pwm charge controller circuit designs. I see that sometimes transistors are used, and sometimes a configuration of capacitors and resistors and diodes. Also, does frequency matter?

 

I haven't noticed any 555 timers so far in pwm charge controller circuit designs.

I suspect that's because in a charge controller these days, a single micro-controller would be used to generate not only any PWM signal required but also to do all the other housekeeping tasks necessary in the control process.

 

I suspect that's because in a charge controller these days, a single micro-controller would be used to generate not only any PWM signal required but also to do all the other housekeeping tasks necessary in the control process.

Well yeah MPPT controllers are definitely more popular now. I just don't know how to program a microcontroller so I am wanting to make a PWM controller.

 

Then a 555-based solution may meet your needs.

 

What is the Peak-Output-Voltage of your Solar-Panel ?
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If you can't do a MPPT by the usual Perturb & Observe, or impedance methods, then regulate the panel voltage - the voltage at which peak power occurs changes very little with light intensity, but you will have to temperature compensate as it varies considerably with temperature.