Sealed lead-acid battery is a liquid battery that cannot be opened. But liquid batteries must always be mounted upright.

Hello, I don't think so, as it's an acid battery, if you coat it, some of the plates could end up without acid. To be sure, send an e-mail to the manufacturer ( biuro@armac.pl ), best regards Claude.

Unfortunately I can't answer that, but itdoktor has answered the question. I also install it upright.

It is closed, so I would say "yes".
But I would look for the detailed data sheet on the Internet, where it is written in detail.