Is the homebrew weapon attack cantrip 'Battery' balanced?

Question

I have created some new cantrips which include making a weapon attack as there are only two official ones to choose from. I've tried to follow these principles based on Booming Blade and Green-Flame Blade:

• Melee weapon attack only, 5 foot range
• No unavoidable extra damage to the primary target at level 1
• Damage no more than 2 targets
• Spellcasting ability modifier doesn't have to affect the spell at all
• Only available on the Warlock, Sorcerer and Wizard spell lists

But with such a small amount of official content to compare them against, it's hard to say if they're balanced.

Is this spell balanced with Booming Blade and Green-Flame Blade?

Battery

Evocation cantrip

Casting Time: 1 action
Range: 5 feet
Components: V, M (a weapon)
Duration: 1 round

As part of the action used to cast this spell, you must make a melee attack with a weapon against one creature within the spell's range, otherwise the spell fails.

On a hit, the target suffers the attack's normal effects, and you become charged until the end of your next turn. While charged, you deal an extra 1d8 lightning damage when making a melee attack with a weapon. If you become charged while you are already charged, the charged damage increases by 1d8, up to a maximum of 2d8.

At 5th level, the attack deals an extra 1d8 lightning damage to the target and the maximum charged damage increases by 1d8. The damage roll and maximum charged damage increase by 1d8 at 11th level and 17th level.

Answer 1

This spell is overpowered. Someone just attacking will have more consistent damage, but there are enough ways to abuse this that you should be able to regularly deal more damage.

If you compare a caster of this spell using a rapier to a fighter using a greatsword you see that this spell allows the user to deal too much damage.

As a base for damage the rapier user is doing an average of 4.5 damage and the greatsword wielder deals 7 damage. However, if the rapier user hits their damage goes up to 9 on their next attack, and 13.5 on any subsequent attacks (assuming they keep hitting).

At 5th level, this gets even worse, with 2 attacks the greatsword fighter gets up to 14 damage per turn. The rapier user takes a little longer to charge this time, going from 9 on the first turn, to 13.5, to 18, and finally maxing out at 22.5 on turn four.

11th and 17th levels are similar, the fighter does more damage on the first turn or two, but the Battery user quickly surpasses them.

---

The above example is for if you are using this spell in a relatively 'fair' manner. however, with the right build, this spell is easy to abuse. The first obvious build I thought of was an Eldritch Knight, at 7th level, they gain the ability to make a weapon attack as a bonus action on the same turn that they cast a cantrip. This allows you to take advantage of your charged damage the same turn that you cast the spell, significantly increasing your damage output. And once they are charged up, and they see that the fight is starting to wind down they can just go for normal attacks if they are level 11+.

The other build that can easily abuse this is a sorcerer with the metamagic twin spell and/or quicken spell. These allow you to potentially hit multiple targets in a single turn and thus charge your damage faster.

One thing that might make it more balanced is to give the option to spend an amount of the built-up charge on an attack rather than applying it to every attack (though that would be more of a capacitor than a battery). Another would be to drop the static bonus to damage at 5/11/17 and only increase the charge amount.

Answer 2

This cantrip is too powerful.

There are six melee attack cantrips. Three require an Action to cast, Shillelagh uses a Bonus Action, and the last two are basically cast as part of a weapon attack.

Since your cantrip is most similar to these last two, let's look more closely at them.

• Booming Blade: At low levels, this spell does zero extra damage unless the target willingly moves before the start of your next turn. If the target never moves, they never take the extra damage.

• Green-Flame Blade: At low levels, this spell does zero extra damage to the primary target, and minor damage to an adjacent target.

Your cantrip would basically allow a first level character to wield a long sword and do 3d8 damage per round. Granted, it would take a few rounds to 'ramp up' to this level, but it's easily possible with a well optimized character.

This cantrip really becomes broken when you add some Two Weapon Fighting into the mix. Now a first level character has two attacks per round. That means they'll hit that +2d8 twice as fast and are much more likely to maintain the charge. When fully charged, you're looking at a rapier/dagger combo doing 5d8 + d4 + bonuses per round. At first level. That is WAAY too powerful for a cantrip. Hells, that's more powerful than most 2nd level spells.

---

The possible fix:

If you're looking for a more balanced version, I'd suggest that your cantrip charge the target. Then, once per round when hitting that target, you deal an extra d8 of lightning damage to it. This puts the damage on par with Booming Blade if the target were to move every round.

Even then, it's still an extremely powerful cantrip, as you'll basically be doing an extra d8 of damage every round without spending any of your action economy to cast a leveled spell like Hex or Hunter's Mark.

Honestly, to really be balanced, I think making the damage type a d4 would be the way to go.

Answer 3

It is okay, counting that you are making only one attack each round. But I can see it going out of control on classes that can multiattack.

As it is, I would veto this cantrip. To avoid arguing with the players. But you can also talk to them about how they intend to use this cantrip in their builds.

But you can fix that adding to the "until the end of your next turn" the clause "the next melee attack that you hit". Makes a little worse but avoid problems.

Answer 4

I don't think about this as OP cantrip, because you are Casting Spell (Cantrip). Fighter can use weapon to Multiattack, Cantrip can't do this (without Metamagic and even with - no more 2 cantrip forever).

And because you need another turn to activate his power, his damage good only in long fights. After 5th level Green-Flame blade/Booming blade can damage +2d8+spellcast mod in same round and kill the Danger, before enemy will act.