Dc Dc Converter for Solar Charger

Hi guys, im trying to complete a solar charger that charges a 12V 1.2Ah lead acid battery. The circuit below is the circuit of the solar charger without the dc dc converter. The problem now is what dc dc converter should i use and at what voltage? and also how do we know the duty cycle and capacitance or inductance to use? I'm not familiar with the dc dc converter. Much help would be appreciated. Thanks!

Buck or Boost? Depends on solar panel output. If max. open ckt. V is around 20 V, best production then would be if battery loaded panel down to about 70% or 14V, no buck or boost needed. Lots of past interest on Buck-Boost in AAC. On page heading All About Circuits, upper right find white box, fillin buck or boost.

Yup, the max. open ckt V is 21.7V with a power of 42W for the solar panel. Got it, thanks! Another question, if i decide to have a dc dc converter constant output a 16v from the solar panel, i can regulate the voltage down to 16v for any voltage that is above 16v generated from the solar panel. but for any voltage below 16v generated from the solar panel, i would have to use boost converter right? will the boost converter be able to output a constant 16v with the constant variation of the generated input voltage from the solar panel?

thanks!

Just thought you might be interested in this?

It was proposed recently to use a boost first- say 10 to 20 in for a fixed 25 V output, then bucked down to 16 or desired V; numbers may have been different. Looks like over kill to me, I'd just feed panel into charger.