possibly they are referring to the older "gel batteries" which should not be fast charged or over heated damages the gel). The newer "AGM" batteries should work fine.

There has always been a lot of confusion about "gel", "maintenance free" and the newer "AGM" (advanced glass mat). They are all different.

 

I would say, cause it's probably been determined or possibly proven by others that it ISN'T A GOOD IDEA! :laugher

 

not sure what a "DEEP CELL" battery. Did they mean DEEP CYCLE? It would help if you said what make/model charger you have.

 

Yep

Could have been lost in translation.

 

Well I don't have much idea about the deep cell batteries because I m looking for the same information.I m now thinking to have the solar charger for it.I think that may be a good option.