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Important Q for electrical engineers: Covering solar panels for Panama Canal transit - possible damage?


Kelly Ran
 

Scott, I reread your message and saw you have your panels in parallel - do you have blocking diodes at each panel? These would be necessary to prevent current in your open-circuit situation. If you have blocking diodes (not the same as bypass diodes) then you are OK. 


On Wed, Mar 4, 2020 at 1:40 PM Kelly Ran <naryllek@...> wrote:
Hi Scott,

open circuiting the panels, as you said, means no current and no hotspots/damage.
just wanted to clarify, the switches are between the panels and charge controllers, NOT between the controllers and the battery? (If the latter, you should make sure you shade the panels first before you open the switch. depending on topology, some charge controllers do not like getting their output open circuited under load.) Seems like the former so you're OK.

now the bypass diode issue is different, in partial shading, bypass diodes should *bypass* shaded modules and reduce panel hotspots. the diodes should be sized to carry a lot of current & not get damaged. another issue for another time. 

happy crossing
kelly + ryan
SM233 Iteration
Boston

On Wed, Mar 4, 2020 at 8:58 AM Scott SV Tengah <Scott.nguyen@...> wrote:
All,

We are scheduled to transit the Panama Canal today and I'm trying to be extra careful with respect to covering the panels to avoid damage by the monkey fists thrown by the canal advisors.

Our intent is to use an extra sunbrella cover first and then put the cockpit cushions on top of that. I do recall somewhere that having complete shading on some parts of the panel but not others (as will happen with putting cockpit cushions on them) may cause hotspots and damage to the diodes.

Any electrical engineers or more experienced folks have an opinion on this?

We intend to turn off the master switches for pos/neg that are installed specifically for the solar panels. The 3 panels are setup in parallel, fyi. That should open circuit them and cause no current to flow and hence eliminate risk of damage, no?
--
Scott 
2007 A54 #69
SV Tengah
http://www.svtengah.com


Kelly Ran
 

Hi Scott,

open circuiting the panels, as you said, means no current and no hotspots/damage.
just wanted to clarify, the switches are between the panels and charge controllers, NOT between the controllers and the battery? (If the latter, you should make sure you shade the panels first before you open the switch. depending on topology, some charge controllers do not like getting their output open circuited under load.) Seems like the former so you're OK.

now the bypass diode issue is different, in partial shading, bypass diodes should *bypass* shaded modules and reduce panel hotspots. the diodes should be sized to carry a lot of current & not get damaged. another issue for another time. 

happy crossing
kelly + ryan
SM233 Iteration
Boston

On Wed, Mar 4, 2020 at 8:58 AM Scott SV Tengah <Scott.nguyen@...> wrote:
All,

We are scheduled to transit the Panama Canal today and I'm trying to be extra careful with respect to covering the panels to avoid damage by the monkey fists thrown by the canal advisors.

Our intent is to use an extra sunbrella cover first and then put the cockpit cushions on top of that. I do recall somewhere that having complete shading on some parts of the panel but not others (as will happen with putting cockpit cushions on them) may cause hotspots and damage to the diodes.

Any electrical engineers or more experienced folks have an opinion on this?

We intend to turn off the master switches for pos/neg that are installed specifically for the solar panels. The 3 panels are setup in parallel, fyi. That should open circuit them and cause no current to flow and hence eliminate risk of damage, no?
--
Scott 
2007 A54 #69
SV Tengah
http://www.svtengah.com


Scott SV Tengah
 

All,

We are scheduled to transit the Panama Canal today and I'm trying to be extra careful with respect to covering the panels to avoid damage by the monkey fists thrown by the canal advisors.

Our intent is to use an extra sunbrella cover first and then put the cockpit cushions on top of that. I do recall somewhere that having complete shading on some parts of the panel but not others (as will happen with putting cockpit cushions on them) may cause hotspots and damage to the diodes.

Any electrical engineers or more experienced folks have an opinion on this?

We intend to turn off the master switches for pos/neg that are installed specifically for the solar panels. The 3 panels are setup in parallel, fyi. That should open circuit them and cause no current to flow and hence eliminate risk of damage, no?
--
Scott 
2007 A54 #69
SV Tengah
http://www.svtengah.com