OK to use trickle charger on Optima battery?

[gmercoleza]

Like the title of the thread says...

My friend's Optima was run down over the last couple days by his radar detector. Vehicle won't start now, since it's cold here and being a diesel he has to glow it for a few seconds.

Anyway, I lent him my jumper cables and my jumpstarter/trickle charger. If his battery won't take a quick jump then I told him to pull it and bring it into the house to charge it (he lives in an apartment and the parking garage does not have outlets).

Anyway, is this OK to do on an Optima? Also, since it is a gel or dry cell, does that mean there won't be any explosive hydrogen cloud?

TIA