No, it should be safe to hook it up and just let it do its thing... if you use the "recond" mode, you might want to loosen the caps... don't need to take them off, just keep them loose so crap doesn't fall in... this will help the battery vent better... you'll want to clean the battery well before you loosen or remove the caps though.... it's a good time to top it off with distilled water anyway... I recommend FRESH, brand new from store distilled water as one that's been sitting around for a while will get ionized from stuff in the air... use the left over to top off the coolant reservoir (few ounces will not hurt, just don't use it to refill/change the coolant) and for your iron or steamer in the house... will keep them clog free
You can use a clean funnel, but I prefer to use a syringe to squirt water in, that way it's controlled and spill free... you can pick up one from the drug store.... they sell big ones that are not meant for injection use
the goal is to put in as pure water as possible so it won't destroy the battery cells from contaminants... you'll need to check again in after summer as the summer heat will cause some water loss in the battery