De or het reservebatterij?

The correct Dutch article is:

de reservebatterij

Rule Words ending in -ij and -erij: usually de. See the rule

How to use reservebatterij

the reservebatterijde reservebatterij
this reservebatterijdeze reservebatterij
that reservebatterijdie reservebatterij
our reservebatterijonze reservebatterij
your reservebatterijjouw reservebatterij
every reservebatterijelke reservebatterij
which reservebatterij?welke reservebatterij?
a big reservebatterij / the big reservebatterijeen grote reservebatterij, de grote reservebatterij