Buck or boost depends on your voltage level. If solar output voltage is always lower than battery charging voltage, then boost. Else, buck.

I think Buck Boost Converter will be Preferable.

The DC voltage from the PV panel varies with the light intensity which depends on time of day and temperature. Similarly on the Battery side the voltage varies depending on the load connections. Thus for optimal charging of battery it is important that the voltage of the PV panel and the current matches the battery charging state at any instant.

This paper shows all the Design calculations and simulation results of a

Buck - Boost converter as depending on the weather condition the Solar

Charge Controller will take the voltage input from the Solar PV panel and convert it to that required for optimal charging of battery.

   Refer Link: 

       http://www.ijeijournal.com/papers/v2i3/H02035962.pdf

       International Journal of Engineering Inventions e-ISSN: 2278 -7461,p-ISBN: 2319 - 6491 Volume 2,Issue 3 (February 2013)PP:59-62

     Design and Simulation of DC-DC Converter Used in Solar Charge Controllers

    Arjyadhara Pradhan, Dr S.M Ali,Chitrlekha Jena, Puspapriya Behera

P.S.

Hi dear;

this is depend the output voltage of panel and battery.

I think you need buck-boost dc to dc converter.

Best regard

salehi

buck boost is needed .. depending on requirement it will charge and discharge

Both may be used according to your application voltage range.

Always go for buck-boost converter for solar applications since the output voltage of panel varies in accordance with the photo intensity of sun