PD has a few features. if it sits in "Float" for over 20 hours it does a quick (15 minutes as I recall) Equalization/desulfate cycle that may well improve battery life. It is much more reliable (Mu first lasted over 12 years) and it is made in the USA (When it failed I dropped in on the factory in Marshall, Michigan at the corner of Industerial and old US-27 whatever they call it now days, about half a mile south of the Brooks Memorial Fountain) and walked out with a refurburished unit.