Actualy i have more the problem that becoz the of the slowness of the prog, the hyteresis switch off too slowy so sometimes its 14.7.. sometimes 15.2 or more.. depend how strong the current is. You have too addapt it anyway too ur battery typ and maybie put the limit of the hyst so that it safely switch off before 14,8V max. (i have red about batts with Calcium-Silver who even like 16-17V.. but u have too read it anyway from instruction manual of ur batt).
The real nice effect with tis hyst-charger, when the sun goes down, the last cycle goes slowy down from 14,7V so the batt is really at 100% when night begins and u need it! Perfect for camping. I never have seen a charger that u can buy do this.
Here is an JPG of the shematic:
