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Topic: Series connected solar cells/batteries (panels) (Read 4 times) previous topic - next topic
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Series connected solar cells/batteries (panels)
Yahoo Message Number: 108613
Bumper 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

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RonB (Bostick) living in San Diego
Original owner of "Bluebelle" a '99 TKB