Using grid type solar panels to charge batteries.

My neighbour has just picked up 3 x 250w solar panels off a house that feeds back into the grid, because the house owner is fitting a larger system.
My neighbour wants to install a 12v stand alone system on a shed in his back yard, using these panels.
I have solar panels for a 12v system and note that the panel voltage is around 18 - 20 volts. His 250w panels are rated at about 30v. Will these panels work without cooking the batteries? Is it just a matter for the regulator to sort out the differences in the incoming voltages? Like to know what others think.