The Lomo LC-A camera is very dependent on its battery. Without a battery the camera will not function at all. With weak batteries the camera will sometime operate intermittently or partially. It may seem silly to stress this, but for some reason bad batteries seem to plague the Lomo more than other cameras. I have lost entire rolls of film due to bad batteries in this camera.
The Lomo is at its best when using the SR44 / S76 silver oxide button battery. It is tempting to use the cheaper LR44 alkaline but it is not advisable. The SR44 is a silver oxide type and will maintain its voltage over its life better than the alkaline will. The LR44 alkaline voltage will sag continuously over it life time.
There are a variety of battery types and designations that will work including: 357 (SR44, PX675S), D303, D357, D303/357, GS13, 228, 357, 280-62, J, SB-B9, SR1154, SR44, SR44W, SR44H, 541, SP357, V357, 4276, KS76, 280-8, SR76E, 1131SO.
In the US batteries marked as 357 or SR44 are easily available and have a shelf life of 8 or more years. Get the right battery, your Lomo will thank you.