I think a gell cell is same as agm. ??? The Heart charger manual only likes wet cell and gell cell batteries
NO, wet and AGM are close in terms of ideal charging curve.
Gel are different.
Wolf10 is correct. According to East Penn, mfg of MK and Oreillys batteries, "charging a gel cell battery as little as .7 volt higher than the recommended 13.8-14.1 volts shortens the life of the battery as much as 60%."
"The gel battery is more starved, giving more protection to the plate; therefore, it is better suited for super-deep discharge applications. Due to the physical properties of the gelled electrolyte, gel battery power declines faster than an AGM battery's as the temperature drops below 32ºF."
The original gel battery that came in many of our FT rvs. $779
8G8D | MK Battery 12v 225 AH Deep Cycle Gel Cell Battery with Automotive Post (https://www.batterystuff.com/batteries/mk-battery-12v-225-ah-deep-cycle-gel-cell-battery-with-automotive-terminal-posts-8g8d.html).
Oreillys AGM8D
https://www.oreillyauto.com/detail/b/fleet---heavy-duty-5000/marine---boat-30733/deep-cycle---marine-batteries-17354/409e0a64fe51/super-start-fleet-heavy-duty-battery-group-size-8d/agm8d/4742645
Pages and pages on this subject, and then double that if you add lithium, lifepo4.
House Batteries, AGM vs gel? (https://www.foreforums.com/index.php?topic=36590.0)
Mine actually came with two Optima batteries. One of the 2 owners before me converted to four, wet cells. Good info and thanks