Tweaking our Solar Power

Changing our Solar Setup from Parallel to Serial Panels

After I updated our Solar Panels in 2020, In July 2023 I found one of the older panels was damaged and the other two were not putting out the expected power. So I decided to update the system.

I built a new Solar Panel Mounting Frame on top of the Bimini and replaced the old panels with 3 new 200W panels. They were connected in Parallel. I also changed out the MPPT Controller with a Victron MPPT 100| 50 Smart Solar Charger. 

The system has been running fine for the past year and they charge my 3 x 100Ah Chins LiFePo4 batteries by noon most days, but then I rarely took them down below 80%.

I'm working on a couple of other projects, one of them being to replace our Propane Cooking equipment with an Induction Cooktop and a Combo Air Fryer / Toaster Oven. From the tests I have done so far the Electrical System will be able to handle that, but it does mean that the SOC will probably drop below 50% more often.

Another project on the drawing board ( ok, Google Drawings ) is adding Davits to the Stern and that means I'll have room for another 200W panel.

With the existing Panels in Parallel the panels combined Voltage is the same as a single panel ( them all being the same size.) but a higher current.  The higher current means a higher voltage drop at the Controller and that's a loss of power.

Ok, where am I going with this?

Should I change the Panel connection to Series?

My conclusion is 'Yes' and here's why.

In Series the panels Voltages are combined but the Current ( ampage ) is not. So the Voltage drop is much less.

If I change to a Series layout, then I could add panels without exceeding the current capacity of the Mppt Controller.

Now, this is an easy process. I simply Turn off the Solar Power inlet to the MPPT Controller, Shade the panels so that they are not producing any power, disconnect the Panels from the Parallel connectors. Re connect them in Series and then turn the power back on.  That took me all of 15 minutes.

No changes needed on the MPPT Controller and, as shown by the graph below the system is fully functional.

The Graph shows the MPPT Controller Input Voltage and Current for the month of August ( 2024) to date ( 18th ) 

It clearly shows that the voltage peaked around 20v and the current at 57amps prior to the system change and then the Voltage peaked to 49v and the current peaked to around 25amps.

Note. On the 16th of August, I ran the Air Conditioning on battery power from around 10am until 11:40am and the Battery SOC dropped to 66.5% and a some of that was with Solar Disconnected.

Back to the Why do this?

• We're going to replace the Propane System with an Induction Cooker & Air Fryer.
• We have learned that we can run our AC on Batteries for about 4 hours, more if we're prepared to expend a Battery Cycle and take them down to 20 or 30%

If we do add Davits and can add another panel, then we'll have 800Watts of and that should improve our Battery Charging time.

Oh, we have a 100Amp Alternator on the Engine but have it detuned to only 75Amps. If we needed to, then we could retune it and run the Engine at high RPM at Anchor ( or on the Move ) to charge the batteries in times of poor solar production.

I'll monitor the system over the next few weeks. We're making progress on refinishing the non-skid areas of the deck and so we'll have the chance to drop the battery SOC when we keep the cabin cooler while we do the work.  Should get some good date.  I'm hoping to see the Solar Production ramp, up in good weather, to over 400 Watts.

Stay tuned.

Want to see the current data? It's shown on Victron World just click here to view Eximius