Now that we have a small supply of fluix crystals it's a good idea to stock up on charged certus quartz crystals. These are found underground (y level is dependent on your mod pack) but are much rarer than their non charged counterpart (Certus Quartz Ore) but these can be manufactured.
A charger will charge crystals if given enough power. You can also attach a hand crank and charge crystals manually although this is slow and not advisable.
Chargers have no interface, right clicking the charger with a crystal in hand will put it into the charger, it will then run and charge the crystal, once the animation stops you can right click the charger again to retrieve the crystal.