Gel Batteries

[ukrsindicat]

Whats going on, Guys?
I have recently picked up couple of 12 v gel batteries. I am not sure if I can replace my old wornout starter cranking batteries with the gel batteries. I am affraid to burn and over charge my gel baterries with the alternator(picture atttached). Also, while they are out, can I charge them with this portable charger ?Picasa Web Albums - Yuriy Tymoshenko - Gel Batteries )?

Thank you, Gents