Series vs. Parralel for Solar Panels

Motor, Motor Maintenance, Winches, Cooker, Heater, Fridge, Battery, Battery Charging, Shore Connection, Instruments, Autopilot, Anchor etc
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Double Horizon
Posts: 440
Joined: Wed 09 May 07, 0:18
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Series vs. Parralel for Solar Panels

Post by Double Horizon »

My biggest power hog is the standard Indel Isotherm fridge with a Danfoss type compressor that draws about 3A when cycled on. Unfortunately it doesn't have great insulation so its duty-cycle is less than ideal (probably averaging more than 50% when you figure day/night). I like to keep it on 24/7, but it hasn't kept up with the refrigerator when I leave the boat on its mooring in hotter weather (>high 80's F) , here at 40-degrees north latitude, with 160 watts of panels. So the power deficit would require me to manually shut off the refrigerator once in a while to let the solar panels (or use charger) to top off the house bank.

I have 8x 20w panels. They were wired in parallel to a MorningStar Sunsaver MPPT 15A solar regulator; parallel for the reason of maximum shade tolerance if one panel became shaded. I decided two weeks ago to re-wire so that they are series-parallel. This has the effect of pairing two panels together in series, and putting each pair in parallel. This doubles the voltage between regulator and panels, and halves the amperage, so that the voltage drop from the wire runs is also halved. It also gives more hours of charging because of the voltages are higher than the nominal battery voltage more hours per day.

This is very important on Dragonfly boats because of the long wiring runs between panels and controller, and difficulty in using thicker wire to reduce voltage loss. So it is a good idea to switch to an MPPT controller and pair your solar panels. (MPPT controllers will do the voltage conversion but PWM controllers will not).

Net result: I no longer have a power deficit -- it's running a surplus! After this weekend my 320AH house bank was at 86%, but last night when I visited the boat the battery monitor read 98% charge. This week has been very hot too, with highs around 90F every day. I opened a cold beer to celebrate!

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Larry - Former Owner DF-1200
EarthBM
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Post by EarthBM »

I've had two 100W panels under the V-berth matress for over a year... The time to install them is now.

How do you run the wires through the aka?
Ivan -- DF 35 #29 "Lykke"
Christian
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Solve the root problem

Post by Christian »

Upgrade the fridge! A new fridge will take 0.4 A insted of 3 A.

I have just installed a new fridge and it works for 24/7 without draining the batteries. Got two panels- one small permanent and a larger flexible - in paralell.

/ Christian
Double Horizon
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Re: Solve the root problem

Post by Double Horizon »

Christian wrote:Upgrade the fridge! A new fridge will take 0.4 A insted of 3 A.


/ Christian
Which model?
Larry - Former Owner DF-1200
Double Horizon
Posts: 440
Joined: Wed 09 May 07, 0:18
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Post by Double Horizon »

EarthBM wrote:I've had two 100W panels under the V-berth matress for over a year... The time to install them is now.

How do you run the wires through the aka?
From aft bulkhead of ama interior, through pivot area, through aft end of aft aka, through aft aka to main hull. I will post a picture showing where in the pivot area.
Larry - Former Owner DF-1200
EarthBM
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Post by EarthBM »

Thanks! I guess the question is about drilling holes in the akas (can't be good) and about flexing cables between the aka and the hull.
Ivan -- DF 35 #29 "Lykke"
Christian
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Fridge I assume

Post by Christian »

The new fridge is Vitrifrigo BRK 35. Works great, 24/7 and the batteries balances around 12.5 v. One large and one small solar pannel gives 1.8 A when the sun shines and that is enough. However I miss the cabin drawer.
Double Horizon
Posts: 440
Joined: Wed 09 May 07, 0:18
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Re: Fridge I assume

Post by Double Horizon »

Christian wrote:The new fridge is Vitrifrigo BRK 35. Works great, 24/7 and the batteries balances around 12.5 v. One large and one small solar pannel gives 1.8 A when the sun shines and that is enough. However I miss the cabin drawer.
I think you are using some kind of magic? The published specification for that model is that it draws 3.1A with the compressor on. In a closed boat (sitting in the sun and with minimal opening of the drawer) you can assume about 50% duty cycle (more in bright sunlight and less at night) and you solar panels will achieve peak power during only a small portion of the day (less with cloud cover and in higher latitudes).
Larry - Former Owner DF-1200
Christian
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Magic it is

Post by Christian »

Been out for 6 days and the battery is steady at 12.6v. The fridge is on 24/7. Every morning it is over 12 v. So it got to be magic. And I do charge phones and computers too.
Double Horizon
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Post by Double Horizon »

EarthBM wrote:Thanks! I guess the question is about drilling holes in the akas (can't be good) and about flexing cables between the aka and the hull.
Here is a photo showing the outboard placement of the holes for the power wire going to aft cross-beams from amas. Note that the arc quadrant where the ama wire emerges is never covered by the swing wing beam, in folded or open position. The inboard end between beams and center hull is easy.

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Larry - Former Owner DF-1200
Steve B.
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Wire thru aka/ama interface

Post by Steve B. »

I installed a HAM radio using the same wiring scheme between aka and ama for the coax and auto tuner.
I mounted the tuner in the port aft compartment.
It would not have been possible for anyone larger than me to get in there to install it !!
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