Quick question on solar instalation

[roland stockham]

Logically it seams to make sense to wire panels in series if you use an mppt controller, less voltage drop due to lower current and starts generating at lower sunlight levels. Is this the way others do it? (obviously keeping Voc within spec for the controller)

[Paul Elliott]

This can work really well, but on a boat shading can be a big problem. A shaded series-connected panel will effectively shut down any other panels in the series string. Bypass diodes (built into some panels) can help, but if you have a shading problem then it's probably better to go with parallel connections, and perhaps per-panel MPPT regulators.

Also, it's not just the voltage limit you have to consider, but the total power limit as well.

Search this forum, there have been a number of discussions here on this topic.

[roland stockham]

Originally Posted by Paul Elliott

This can work really well, but on a boat shading can be a big problem. A shaded series-connected panel will effectively shut down any other panels in the series string. Bypass diodes (built into some panels) can help, but if you have a shading problem then it's probably better to go with parallel connections, and perhaps per-panel MPPT regulators.

Also, it's not just the voltage limit you have to consider, but the total power limit as well.

Search this forum, there have been a number of discussions here on this topic.

thanks for that, panels do have built in diodes and well within the controller limit. Shading should not be a big issue as panels will be on a stern arch outside all obstructions. But made me think, will look up how bypass diods are set up and what the losses are. Also if you go for parallel with a single controller is there a problem with it finding the mpp, hoe closely does it match assuming each panel is the same make and age?

[Paul Elliott]

Originally Posted by roland stockham

[...] Also if you go for parallel with a single controller is there a problem with it finding the mpp, how closely does it match assuming each panel is the same make and age?

Good question. For that matter, could there be a similar issue with series-connected panels? I don't think there will be much of an issue if the panels are of the same type, but I look forward to hearing other opinions, especially if someone has numbers to share.

[Bulawayo]

We always elect to wire in parrallel - and then use a bus bar into the MPPT.

Originally Posted by roland stockham

Logically it seams to make sense to wire panels in series if you use an mppt controller, less voltage drop due to lower current and starts generating at lower sunlight levels. Is this the way others do it? (obviously keeping Voc within spec for the controller)

[tdoster]

Best way for me was to test each way, and I ended up running three banks of solar (6 panels) with two in series that are next to each other and not subject to shading in a hybrid approach.

I tried multiple configurations until I saw the most output under most conditions. Our Midnite Kid Controller also does a better job than our Morning Star for whatever reason - maybe because it was setup by someone who knows what they are doing, and that was not me.

[yachttie]

I agree with other comments.
1 Series is better
2 If shading is a problem, try wiring starboard panels in series, port panels in series then parallel the output of the 2 series into the MPPT controller
3 Panels must be same model, size & brand to work effectively in MPPT.

I use a VSR (Voltage sensing relay) to parallel or separate house from starter batteries but strongly suggest installing a manual override in case VSR fails. This happened to me & you probably won't realise problem until house batteries are nearly flat.

[tinkrman69]

if panels have blocking diodes you'll have to pypass it in the series as it will stop passage from the previous panel in the series. shading will be a problem to consider, as mentioned with remedies in other posts.

[Paul Elliott]

Originally Posted by tinkrman69

if panels have blocking diodes you'll have to pypass it in the series as it will stop passage from the previous panel in the series. shading will be a problem to consider, as mentioned with remedies in other posts.

There are two panel diode configurations I am aware of: blocking and bypass. Neither of these will stop panels in series or in parallel from operating. Depending on your regulator, you may not need a blocking diode. If you can remove it you will gain some power.

Here's an illustration I just found:

[tinkrman69]

Originally Posted by Paul Elliott

There are two panel diode configurations I am aware of: blocking and bypass. Neither of these will stop panels in series or in parallel from operating. Depending on your regulator, you may not need a blocking diode. If you can remove it you will gain some power.

Here's an illustration I just found:

yup, following that schematic will work. But shading on any panel in the series will cause that bank to not produce, as the voltage will be lower than the other bank. one voltage won't add into a higher voltage in a parallel circuit. some will trickle but it won't be significant. but nothing you can do about it as shading on a sail boat is inevitable. when there is sun the higher voltage will carry more amperage.

[SeaSon]

So are the blocking diodes to prevent battery discharge at night, and the bypass to allow one panel to produce current and voltage if another is shaded?