There has been lots of posts on the optimum way to connect

solar panels on a

boat. In series or parallel.

For a long time I have been suggesting people try both metods and report the results.

So far there does not seem to be any practical results.

My

regulator has recently developed a problem, so the

purchase of a new

regulator which will accept a higher voltage. Will allow me to make the change.

As the

wiring is a bit inaccessible I thought I would first do some theoretical calculations to determine the difference.

To make it simple I assumed

2X12v

panels each panel is dived into 2 sub

panels of 6v each with bypass diodes. Each panel can produce in practical conditions 1A

The sub panels are connected in series, hidden within the 12v panel, but we can chose to wire the 2 12v panels in series or in parallel.

In series we have 4 6v sub panels connected in series.

In parallel we have 2 6v sub panels connected in series (because this is how panels are constructed), but the 12v panels are connected in parallel

.

**No shade:**
Series and parallel perform essentially the same. There is a slight reduction in

wiring loss for series connection, and the panels may produce

power slightly earlier and later, but the regulator will be less efficient with the greater voltage difference. Overall maybe a couple of percent improvement with series connection.

Series 2.0+ A

parallel 2.0 A

**Full shade on all panels:**
No advantage with series or parallel connection

Series 0.0 A

Parallel 0.0 A

Full Shade on one Sub Panel out of 4:
If there is shade on one sub panel the result is the same no matter which sub panel is effected

Series 1.4 A (will still have 3 out of 4 sub panels working, but there is some loss in the bypass diodes)

Parallel 1.0 A

**Full Shade on two Sub Panel out of 4:**
Here the theoretical model gets more complex.

If we call the 2 6V sub panel that make up the first 12v panel sub panel 1 and 2. The 6v panels that make up the second panel are 3 and 4.

There are 6 possibilities

Shade on sub panels 1&2

Series 0.9 A ( Not 1.0 A because there will be some loss in the bypass diodes)

Parallel 1.0 A

Shade on sub panels 3&4

Series 0.9 A

Parallel 1.0 A

Shade on sub panels 1&3

Series 0.9 A

Parallel 0.0 A (the voltage is under the nomimal 12v so no

power is produced)

Shade on sub panels 1&4

Series 0.9 A

Parallel 0 .0 A

Shade on sub panels 2&3

Series 0.9 A

Parallel 0.0 A

Shade on sub panels 2&4

Series 0.9 A

Parallel 0.0 A

Overall my theoretical calculations suggest series connection of 24V in a 12v system is better

I will try some practical experiments over the next few days to see if I can get a definitive answer, but my theoretical model supports series connection

Comments welcome.

Note many

solar panel have move sub panels separated by bypass diodes than the 2 I have assumed in this theoretical model, but the calculations and explanation gets more complex without any change in the recommendation.

I have also assumed a reasonably high loss in the bypass diodes.

The calculations are based on a series input of 24V on a 12v system. The calculation for increasing the voltage beyond this I will leave to others, as it is not possible in my system.

I have assumed very deep full shade.