This is the latest version of the onboard charger that I have : Amazon.com : MinnKota MK 220D On-Board Battery Charger (2 Banks, 10 Amps Per Bank) : Boating Battery Chargers : Sports & Outdoors

My MinnKota 220 (2 bank @ 10amps/bank) has done a great job of keeping my Everstart 24DC & 27DC batteries charged & maintained.

Can't speak for other brands, as this is the first & only onboard charger I have any experience with. Bought in 2010 by previous owner of boat.

... cp