It doesn't make any difference if you charge them first or not. Do remove them from the equipment (unplug the connectors at least) to prevent damage should one burst its seal or leak. The most important thing is; when you are going to use them again, to give them a slow charge at c/10 rate. Charge for at least 14 to 15 hours at C/10 the first time after long storage or if new. If you have a cycler, I would do one cycle at least on the units after they are brought back into service.