Series connected solar cells/batteries (panels) December 17, 2009, 12:47:44 pm Yahoo Message Number: 108613Bumper said shutting down almost all the output from the solar panel.> The cells used for single crystal panel arrays each have a bypass diode. This isn't the blocking diode used to keep the solar panel from discharging the batteries at night. The diode is in parallel with each cell. If a shadow were to fall on just one cell, it would become a high resistance and current provided by all the unshaded cells could damage the one not conducting. Instead any voltage over .6 volts (one junction drop)and the current just bypasses that cell. No damage but a reduced voltage output. AM solar's 44 cell panels, even without a sophisticated controller, could tolerate some shading better than a 36 cell array. I have three older Siemens 48 watt panels with only 36 cells. Two panels in series wouldn't electrically be much different than an 88 cell panel providing the nominal 24 volts, over the 44 cell at 12 volts. Kind of like a golf cart battery with three cells, as compared to a 12 volt battery with six cells. I would be concerned about the current capability of the bypass diode. In addition most service technicians wouldn't be expecting series connected panels, that could complicate matters at a later time. Also for future expansion, you would have to add two more panels in parallel, or just one panel in series. With 3 panels in series at 22 volts each, I could see where that might be getting close to presenting a shock hazard. I would opt for the conventional installation of two panels in parallel unless there was a clear benefit otherwise. On a related topic I mounted my solar panels using 27 stainless screws, #8 x 5/8" to minimize penetration into the ceiling on a cold day when the floating roof was stretched tight. Technique is very important using screws. For instance I wouldn't let most Camping World technicians on the roof, much less drill holes! I hope this was helpful, Ron and Bluebelle a '99 TKB[Non-text portions of this message have been removed]