Ooops, I guess I should have included the panel specs in my OP... Here they are
1 of these: Open circuit voltage : 21.9V , Short circuit current 1.27A, 36 cells, Max power Vmp 17.5V, Max Current (Imp) 1.14A,
This is a no name Chinese panel, but they do but out good power, close to their name tag from what I can remember from
my tests last summer. And one amorphous panel rated 15W (thought it was 20), this doesn't haven't any specifications on it though..
I doubt the batteries have any electronics in them as they aren't particularly expensive, the drill is Ryobi if anyone is familiar with those.
I guess judging from your comments that it may work, so....
I think I'll try it and let you know what happens! I'll measure the voltage of a fully charged battery and see what that is