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When used with a properly regulated constant voltage charging system (such as an alternator), the OPTIMA will not emit hydrogen gas. However, gassing can occur when charging at excessive voltage levels or in extreme high-temperature conditions. In automotive applications, this typically will not happen if the alternator/regulator stays below 15 volts.

As intended.

Totally agree all are safe as long as charging equipment works as intended as the Optima website says, however here is a more extensive quote from the Optima site in the section where they answer owner’s questions.

“Mary, our batteries are AGM (absorbed glass mat) lead-acid batteries in a SPIRALCELL design. They are not gel batteries, so unfortunately, we cannot offer advice on how to mount gel batteries safely. However, we can offer advice on properly-mounting our batteries. Any lead-acid battery can vent fumes that are both flammable toxic in extreme situations, so for that reason, we always encourage people mounting batteries in enclosed locations, to make sure they are properly-vented to the outside air. In fact, our D27M D31M BLUETOP® batteries both come with provisions for attaching vent tubes to the outside air. Our batteries can also be mounted in a variety of orientations, although we do not recommend mounting them upside down. If you do mount one of our batteries on it’s side, we encourage you to consider mounting it securely, with the vent ports oriented on the top side of the battery, making sure the terminals are covered and protected from coming in contact with any metal objects.”

Now again I am not trying to get anyone to do anything. Just providing information. What I do wish is manufacturers would stop cutting corners and install compartment vents. 🙂


Steve and Andra
2012 F350 6.2 gasser SRW LB
Fab Fours front and rear in case we run into a rhino
2019 Northstar Laredo SC