Assumption A rod, wand or stave is functionally identical.
Each chargeable device can hold a small number of charges (perhaps 5). This implies that these devices are rare and precious and not to be used lightly... These devices are very difficult to make and charge, as a result it takes much more energy to create an effect that an Archmage or other spellcaster could create in a blink of an eye.
So our heroine uses her rod of blasting and smites the foe...

How does she recharge the rod? Can a rod recharge itself? Yes, is the answer and there are 3 methods...
Recharge over time
Once a charge is used up it takes a very long (1000 turns?) to recharge. It does so by lowering your HP by 1 point.
If you can cast spells then it will also grab a point out of that pool of power (recharge doubled), mana points down by 1.
Note that the Mana pool can be any source of energy. So anyone with access to an additional source of energy has a slightly increased rate of recharge.
Recharge in a shop
Our heroine rich, is not a spellcaster and is impatient with the slow method and so goes to a shop, pays a steep fee and does a recharge of the device.
Recharge as spell
Our heroine happens to be a spellcaster and so finding herself a quiet spot pours her energy into the device to reduce or complete the chargeup time.