Non-matching PVModules

There is really no easy answer to your question without knowing all of the specs. of each PV module along with the specs. on the battery bank and how you use power from them. For example; if you have a 1200 amp hr. bank @ 12v nominal, and in a 24 hr. period you use only 20%, and this happens on a regular basis, then with 120 watts of PV module a charge controller may not be nescessary, especially if the PV modules rated voltage (what I call working volatge) is below 17 volts and you live in a climate that is hot most of the year. I started with 6-MSX 77's; 4.5 amps @ 16.9 volts charging a 1320 amp hr. battery bank. I live in the southeast of USA. At the time we were using approx. 150 amp hrs. in a 24 hr. period. During the summer months I could bypass the charge controller because the battery voltage would never get above 14 volts. 13.8 to be exact. But during winter months I would need the charge controller because without it battery volts could soar to 15. Of course its always a good idea to have a charge controller for safety sake, even though the NEC states an exception when the PV source is only 3% of the battery storge after all NEC factors have been caculated, including ambient tempretures. The NEC book can be purchased at most electrical supply house's for around $35. Its a good thing to have. Article 690 relates to Photovoltaics and the supporting systems.