Typically, a new Jet Ski battery comes Factory Activated, unless marked otherwise on the packaging. Most are charged at the factory, but may still need to be recharged prior to first use to achieve optimal performance.
If you don’t care about optimal performance from the get go, you can run the battery without hurting its integrity and get that full charge you want at a later date.
If you do care about getting the most out of your battery from inception and you know the battery has been stored or sitting on a shelf at a dealer longer than 6 months or if you are able to test the battery prior to installation and it reads lower than 12.60 Volts for a 12 Volt battery or lower than 6.60 Volts for a 6 volt battery, then the battery needs to be recharged.
If you are able to test the voltage of the battery prior to installation and it reads higher than 12.60 Volts or if you know the batteries shelf life is under 6 months, the battery may be installed in the Jet Ski without any refreshing charge.
If the battery is not factory activated, you will have to activate the battery and charge it prior to placing it into service. This typically involves adding Electrolyte to the battery using a funnel, sealing the battery with the provided plugs and applying an initial charge. The battery should come with specific instructions, electrolyte and the tools to do this. It should also include a chart showing the proper charge time for the battery.
After verifying your battery is fully charged, a good rule of thumb is to use a trickle charger/ smart charger. A charger of this type will keep your battery ready for use while preventing overcharging. Two good trickle chargers are the NOCO genius charger and the Power Sonic Battery Sitter.