Battery Minder/Charger for 915iS

The engine type isn't relevant.  The battery charger/maintainer you choose needs to be compatible with the chemistry of your battery.  If you have a lead-acid battery, then the unit that you used for your C-182 will work fine.  If you have a lithium-based battery then you'll want to find a charger that is specified for that type of battery.  Aviation lithium batteries are typically LiFePO4, or lithium iron phosphate.  The battery manufacturer is the best place to get specific charging recommendations.

Thanks.  Will have to look at the battery to figure it out.  Pretty sure it is not lithium, but it looks like it is a sealed battery made in Brazil.  Montaers are made in Brazil. But have no idea if it equivalent to a Concorde or other US battery.