what if i make a 20v panel for charging a 12v battery,will that be ok or will it damage the battery
Well, that depends.
If you're going to connect it directly to a battery, and the battery is high enough in Amperage say 18Ahrs or more then it should not hurt it. The battery will hold the panel output down to its voltage.
In a perfect world you would be getting the full 1.75A directly into the battery, it would take more than 8 hrs to full charge a 18Ahr battery, so you run little risk of hurting either the panel or the battery.
IF you are looking to connect the panel to a controller or a MPPT then the voltage could be a concern. The HF panels normally run 21 - 23Vdc Open circuit and they don't hurt either unit. I have Ghurd's controller connected to my setup to keep my batteries charged, then dump the excess to another set of batteries,etc.
20V at 1.75A is ~33 watts. 33 watts at say 13.5Vdc (Acid based batteries) is ~2.4A . 2.4A could charge a acid based battery in about 7 1/2 hrs.
Still would not hurt the battery,
UNLESS you left it charging like that every day.
The 18V setup would then leave you enough panels to build a smaller unit for AA charging or ...
Hope that helps;
Bruce S