Manatech

One of the most important innovations of the Third Age is Manatech. These wondrous devices incorporate a "spell plate" that is effectively a reusable spell scroll.
There are three components that make up a manatech device: the Spell Plate, the Mana Accumulator which provides charges and Conduit material that links the two. Charges from the accumulator are used at a rate of 1 per spell level for each casting. The magical energy refreshes over a long rest. Small Accumulators (up to 6 charges) regain 1d4+1 charges. Large accumulators (7-12 charges) regain 1d8+2 charges. Damaging cantrips only use half of a charge and non-damaging cantrips use special accumulators that continually refresh themselves so they have (effectively) unlimited uses.
Almost any Cleric or Wizard spell 4th level and lower can be made into a manatech device. The base item can be anything as long as it is large enough to accommodate the spell plate (size of an index card) and the mana accumulator (size up to a large battery). Examples include a rod or staff (most wands are slightly too small), household items like lanterns or cooking utensils, bracers, specially-designed cloaks, shields or rigid armor like a breast plate. Ranged weapons like bows or crossbows are also popular for damaging spells, but melee items are not advisable as manatech is somewhat fragile and tends to break if struck hard.
There are limits to what can be done with manatech:

• Only one "concentration" spell may be active at a time (in addition to one that a caster maintains). Concentration checks made by the item have no Constitution modifier but Proficiency does count.
• Spells of 4th level or less, from the Cleric or Wizard lists only
• Spells that require expensive and expendable material items cannot be used (like gems or gold dust) However, see the Expendable Component House Rule.
• Activating a manatech device takes the same time as the spell. Deactivating a plate requires a Bonus Action.
• Spells are cast at the base level only (cannot up-cast)
• Spell Save DC's are at DC 13
• Attack Spells use either Wisdom or Intelligence for the Spell Attack roll (user's choice) though specially made weapons could use Dexterity as well.
• Spells with a variable effect like Prestidigitation or Chromatic Orb can only have one effect, such as Warming or Cleaning for the former or Fire Orb for the latter. This does not includes Illusion spells that create sensory effects such as images or sounds. They are cast as normal.
• No item can accommodate more than one spell plate.

If a manatech item is targeted by Dispel Magic, it will cancel any active spells being maintained in addition to draining 1d3 charges.
Any manipulation of manatech devices, such altering or repairing a device requires proficiency in Tinker's Tools. Changing an accumulator takes roughly ten minutes. Repairing or altering a device (like changing a spell plate or transferring a plate to a different item) takes 1-4 hours depending on the complexity of the change. This requires the use of a tinkering workshop. Someone with the Manatechnician feat can do this without a workshop but if they do use a workshop, it takes half the time.
Only someone with spell-casting ability can create spell plates and only for spells that they are able to cast. Creation of accumulators requires a specially etched gemstone of sufficient quality (25 gp per charge or 10 gp for minor accumulators) so Jeweler's Tool proficiency is extremely helpful (though not required).
Accumulator Interference: Carrying multiple active devices will cause problems. More than five devices (with attached accumulators can cause Spell Failure. When activated, roll 1d20.

Six devices - the spell fails on a 1-5

Seven devices - the spell fails on a 1-10

Eight devices - the spell fails on a 1-15

For more than eight devices, the device will not activate at all. On a roll of 1, the device "shorts out". To repair, the device, it takes one hour and 20gp worth of materials.
In addition, while carrying five or more drained accumulators, they won't recharge unless they are spread a significant distance apart. Also, accumulators will not recharge while placed in a pocket dimension (like a Bag of Holding or a Wrist Pocket).