Solar Panels....in parallel or series?

[lupins]

I've known this to be a highly debated topic with there being pros and cons for both setups but was interested on which way I should go! I have purchased x2 12v 115w Victron solar panels that are to be mounted onto the push pit. They will be attached to a set of NOA adjustable brackets allowing them to be tilted inboard and outboard, however, they will be slightly limited on the inboard tilt so wont always be able to track the sun entirely throughout the day, but for most of it. The panels will be wired into a Victron 75/15 MPPT smart solar unit. My understanding is that if there is any risk of shading, wire in parallel as this will ensure ultimate efficiency as the output of one panel won't effect the other. However, if there is little/no risk of shading occurring, then wire in series. I have branch connectors and enough cable to wire in parallel, but wanted to clarify what anyone else would do in lieu of the above.

I look forward to hearing your feedback! Have a cracking weekend!

 

[wiggy]

Parallel.

 

[yotter]

Parallel also, I have 2 x 80W Photonic Universe. I fitted 2 inline Diodes as advised by them. Apparently in case one panel is shaded, they should improve efficiency. Not trying to highjack thread, so apologies if it does.

 

[PaulRainbow]

If no great risk of shading, wire in series. Your Victron controller will start working earlier in the day.

 

[noelex]

The highest output on a boat is generally achieved with parallel rather than series connection, but the wiring cost and difficulty of installation is slightly higher.

A final option is one controller per panel. This tends to give the highest yield of all. A valuable added benefit is redundancy. This method is more suited to larger arrays, but can be used successfully with only 100w panels.

Two controllers are more expensive than one, but they can be smaller 75/10 models (because each only has to handle half the current) that are slightly cheaper than the larger 75/15 model, helping offset some of the cost.

 

[lustyd]

.

 

[GHA]

Parallel here, just a little shading made big difference in series & shading pretty much impossible to avoid on a sailing boat.

 

[Bobc]

Tried my 2 panels in series but found that I got more out of them in parallel.

 

[RobbieW]

I appreciate you have your panels so my approach wont work for you. Rather than install 2x100 panels, I installed 4x50 and have them wired in series/parallel diagonal pairs on the stern arch. As others say, shading is the killer to output.

 

[Shaddickp]

Parallel also, I have 2 x 80W Photonic Universe. I fitted 2 inline Diodes as advised by them. Apparently in case one panel is shaded, they should improve efficiency. Not trying to highjack thread, so apologies if it does.

Are blocking inline diodes necessary if you are using a controller, I thought not. I say this because in nearly all cases a controller should be fitted.

 

[noelex]

Are blocking inline diodes necessary if you are using a controller, I thought not. I say this because in nearly all cases a controller should be fitted.

If you have a solar controller that disconnects during low light conditions, and nearly all solar controllers fullfil this requirement, then a blocking diode will have a net loss on the output. This especially applies to low (“12v”) panels.

There are exceptions, especially when solar panels are covered in snow for prolonged periods, but these condtions are not commonly experienced. If you are expecting these conditions disconecting the solar controller completely is a better solution.

 

[Graham376]

Are blocking inline diodes necessary if you are using a controller, I thought not. I say this because in nearly all cases a controller should be fitted.

Depends on the controller, I had a cheapish Chinese one which allowed reverse current at night but the Victron I have now doesn't.

 

[yotter]

Its a Victron MPPT controller, if I do not need the blocking diodes, very happy to remove them (I only fitted them as advised by Photonic Universe, perhaps they assumed I had a cheapish Chinese controller). I think they were fitted in case one panel was shaded and the other not to prevent reverse current flow in the shaded panel. It will remove more 4 more poor contacts in the wiring also

 

[noelex]

Its a Victron MPPT controller, if I do not need the blocking diodes, very happy to remove them (I only fitted them as advised by Photonic Universe, perhaps they assumed I had a cheapish Chinese controller). It will remove more 4 more poor contacts in the wiring also

Yes, the output will be (slightly) higher if you remove any blocking diodes. However, do not remove any bypass diodes. These serve a different function and need to be retained.

Nearly all solar panels have bypass diodes when they are manufactured, wheras blocking diodes (if used) are added externally by the installer.

Occasionally blocking diodes are added instead of fusing between the controller and the panels. This is not recommended, but if you have three or more solar panels check there is not a requirement to replace the blocking diode with a fuse.

 

[yotter]

Yes, the output will be (slightly) higher if you remove any blocking diodes. However, do not remove any bypass diodes. These serve a different function and need to be retained.

Nearly all solar panels have bypass diodes when they are manufactured, wheras blocking diodes (if used) are added externally by the installer.

Occasionally blocking diodes are added instead of fusing between the controller and the panels. This is not recommended, but if you have three or more solar panels check there is not a requirement to replace the blocking diode with a fuse.

Many thanks,
Sounds like the best plan is to remove them. The panels are good quality (German or Austrian?) from PU, so should have the bypass diodes. Is a fuse to protect the cabling, if so, hopefully it can be fitted inside the boat. The max current for the panels is around 4 to 6 amps, so perhaps a 10 amp fuse would be appropriate. I have one between the controller and the batteries already.
Many thanks

 

[noelex]

Many thanks,
Sounds like the best plan is to remove them. The panels are good quality (German or Austrian?) from PU, so should have the bypass diodes. Is a fuse to protect the cabling, if so, hopefully it can be fitted inside the boat. The max current for the panels is around 4 to 6 amps, so perhaps a 10 amp fuse would be appropriate. I have one between the controller and the batteries already.
Many thanks

All solar panels need a fuse between the controller and the battery, only some installations need fusing on the solar panel side. As a general rule If you have have a string of three or more panels this additional fusing is needed. Each string or panel needs a fuse in this case.

The adittional fusing is generally needed to protect the interal wiring of the solar panel from overheating in a fault situation. A blocking diode also provides some protection and is sometimes used instead of a fuse. Most comercial standards do not accept using a diode for this purpose, but if removing a blocking diode you need to be careful that it has not been installed for this reason.

A simple rule is If you have less than three panels conected to a controller removing a blocking diode is unlikely to cause any safety concerns.

 

[Nina Lucia]

I recently watched this one, as we doing similar project on very similar boat:
Solar Panel Installation on a Small Sailing Yacht

 

[billcole]

A final option is one controller per panel. This tends to give the highest yield of all. A valuable added benefit is redundancy. This method is more suited to larger arrays, but can be used successfully with only 100w panels.

Two controllers are more expensive than one, but they can be smaller 75/10 models (because each only has to handle half the current) that are slightly cheaper than the larger 75/15 model, helping offset some of the cost.

So can you connect two MPPT controllers to feed the same battery bank without them confusing each other ?

 

[noelex]

So can you connect two MPPT controllers to feed the same battery bank without them confusing each other ?

The short answer is yes.

The settings need to be correct, often using some of the advanced options. Even then there can be some occasional conflicts, but these are usually of a minor nature.

These minor conflicts can be eliminated completely if the multiple solar controllers can comunicate between themselves and synchronise their output. This is worth doing, although there are generally no significant problems and still a worthwhile net gain from the better tracking if this is not possible.

Synchronisation can be done with some solar controllers. The popular Victron Smartsolar controllers have this feature built in, but you need to enable this option. This is not difficult. It only involves alltering some settings using the app. As the units comunicate via Bluetooth there is no extra wiring needed.

 

[billcole]

The short answer is yes.

The settings need to be correct and even then there can be some occasional conflicts, but these are usually of a minor nature.

These minor conflicts can be eliminated completely if the multiple solar controllers can comunicate between themselves and synchronise their output. This is worth doing, although there are generally no significant problems and still a worthwhile net gain if this is not possible.

Synchronisation can be done with some solar controllers. The popular Victron Smartsolar controllers have this feature built in, but you need to enable this option using the app.

Interesting, thanks