You will be glad to know that the batteries of Nokia Lumia 535 and Lumia 540 are inter changeable. This mean you can use Lumia 535 battery in Lumia 540 and vice versa. Interestingly the Nokia Lumia 540 battery capacity is 2200mAh, and Lumia 535 battery capacity is 1900mAh.
According NokiaViews reports, simply swap the battery of Lumia 535 and you will get up to 14 percent improvement in battery life.
The Lumia 535 comes with a 5 inch qHD whereas the 540 packs HD resolution which is 1280 x 800 pixels. Also note that the 540 packs 8MP rear camera while the 535 has just 5MP shooter.