Unlike the other heroes, the Battle Machine will not defend. This is because the Battle Machine is either away attacking another base or is being upgraded and thus unable to fight.
However, its altar will still be there, and you will be able to move it if the Battle Machine is rebuilt. In that case, Versus Battle opponents will be able to attack it.
At level 5, the Battle Machine unlocks the Electric Hammer ability. The ability electrifies the hammer, causing the Battle Machine’s damage to increase for the next three hits, in addition to regenerating a fraction of the Battle Machine’s health and slightly increasing his speed. Unlike other heroes, the Battle Machine can use its non-passive ability multiple times in the same battle.
The Electric Hammer will end prematurely if the Battle Machine does not get three hits within 15 seconds of using the ability (but by then, the Electric Hammer will have recharged).
When the ability is being activated, the Battle Machine is momentarily stunned while it raises its hammer to get struck by lightning.
The Battle Machine can currently only be upgraded to level 30.
Clash of Clans Battle Machine Offensive Strategy
Use the Electric Hammer ability when the Battle Machine is next to high hitpoint buildings or crowded areas to get more destruction. You can also use this strategy against high-damage buildings to prevent the threat from them staying up too long.
Make sure not to activate Electric Hammer when the Battle Machine engages the Guard Post (unless you are in desperate need of health) as you will be wasting your damage on overkill.
This ability is especially deadly against the Crusher(s), as it helps him withstand a lot of damage as well as take it out if it is all by itself.
A Battle Machine going 1 on 1 against a relative level Crusher can take it out without using the ability.
He can tank for troops such as Sneaky Archers while they do the damage behind.
The Battle Machine has no actual preferred target but you want to be wary with crushers because the AI seems to prefer them. Before deploying him, try to destroy the Crushers (as he is weak against them) and all the buildings around the side so that he doesn’t wander off to the sides.
If you have unlocked the Battle Machine’s ability, a good strategy is to deploy the Battle Machine in a corner and immediately use its ability. The Electric Hammer lasts until the Battle Machine gets three attacks, so by the time it wears off, the ability is much closer to being fully recharged than if you deployed it and used its ability normally. This means that early on the Battle Machine would quickly be able to get six hits with increased damage as opposed to three.
In addition, if you are using a Night Witch-based attack, this saves them from Mega Mines/Hidden Teslas placed in the corner as well as mitigating damage for the Battle Machine if they do exist.
If there’s another building, do not trigger the ability before destroying the buildings, you’ll need the damage bonus on more threatening buildings such as strong walls.
Using the Electric Hammer at the end of the Battle Machine’s swing (before the damage is done) is the most efficient. If you use the ability at that time, his auto-attack will be canceled but the next auto attack will be performed without the swing.
You can allow your troops to do damage to the base before sending in the Battle Machine to destroy the Builder Hall (if it has not been destroyed) and/or finish off the remainder of the base. An example would be using an all-Baby Dragon attack with the Battle Machine; the Baby Dragons can destroy a large portion of the base before the Battle Machine is sent in to destroy the Builder Hall.
Be careful to not put troops directly behind the battle machine as they can all be damaged at once by splash damage (e.g. Multi Mortar, Roaster) and traps (e.g. Mine, Mega Mine)