Foretravel Owners' Forum

What say the council? I have 2 420W 73.6 v panels, they are hard to come by. So here is the question, if I did 2 215w 39.3v panels in series then in parallel with one of the 420 watt panels. I have an outback 80 MPPT solar controller 150v max voltage #4 copper to the controller.  I need to keep the voltage below 150.

I think that is 960 watts max output.  With some conversion losses 2 215 in series and in parallel with one 420 watt panel should be OK.  I would ask Alan at Bay Marine or somebody at AM Solar.

I have  4 300 watt panels in parallel.  This minimizes the effects of shade.  Each panel puts out whatever voltage it does and they get combined in a fuse block just before my Victron solar controller.

I will be interested to hear other ideas.

I have 4 panels like Rogers. I want to add 2 additional panels but don't have the room for 2 panels like I have.
I asked Alan, he suggested an additional controller since I was already maxed with the 85/150 Victron.
I think I will go with  LG panels that will put out about 360 watts each, they are smaller and more efficient and will fit my size restriction. I will add a second controller for these two panels. All wired in parallel as Roger suggested.

Bruce, you have two 420W 73.6 v panels and Two 215w 39.3 v panels.
I assume the the voltages you have provided are VOC (volts open circuit), but what is needed to pair panels in an array is the Maximum Power Point voltage (Vmp) and amperage (Imp).
I calculated from the VOCs that the 420W panels are circa Vmp = 58.5 v and Imp = 7.2 amps, while the 215W panels are circa Vmp = 31.2 v and Imp = 6.9 amps.
I also have an Outback 80 Controller, which will measure VOC every few seconds to maximize the wattage going to your batteries by holding the panels at Vmp.
I would series a 420W with a 215W for VOC 112.9, Vmp = 89.7 v, and Imp = circa 7.0 amps. Parallel this pair of panels with the other two panels in series for about 14 amps total.
You may not get the maximum amps from the 420W panels but your Outback Controller will function as designed.

Roger, with four 300 watt panels in parallel, each panel will output at exactly the same voltage but will provide whatever amperage that it can. A panel in the shade will output less amps than a panel in the sunshine, but at the same voltage.

Lon:
Do you intend to pair another 85/150 Viltron with the one you have?
I am not sure that two controllers connected to a battery bank can be synchronized, particularly when changing from Absorb mode at circa 14.5 v to Float mode at circa 13.6 v.

I had the same question, I have three 320 panels in series to a Victron 60/150 and three 165 watt panels in series  to a Midnite solar 30/150. Alan at Bay Marine said they may not switch to float at the same time but will not make much difference in charging. He said with my different VOC's, on each string, separate controllers is probably the best way.

I would have to confirm with Alan, but, I thought he said that multiple Victron charge controllers will communicative with each other.

Whenever there are multiple battery chargers, like alternator, solar, 120-volt battery charger or more than one solar controller, etc, the one with the highest voltage will often 'fool' the others to thinking the battery is fully charged when it is not. This is not an easy thing to fix and the easiest way is to only have one on at a time.

Said another way, when a battery is low, the charger with the highest amp capacity will get the battery charged faster, and most chargers measure battery charge level from voltage reading, regardless of how many amps have been restored.

So, when a solar panel under low sun is putting a few amps into the battery at a high voltage, the 120-volt charger may stop pumping amps at the correct voltage, because it thinks the high voltage reading is coming from the battery, when it is just coming from the solar controller.

It is possible to finely coordinate but the simple solution may be to just have one on at a time, so multiple solar controllers can introduce problems.

Wyatt,
"Roger, with four 300 watt panels in parallel, each panel will output at exactly the same voltage but will provide whatever amperage that it can. A panel in the shade will output less amps than a panel in the sunshine, but at the same voltage."

My panel's output voltage and amps vary with sunlight intensity.  Are you saying above because they are in parallel? And at some point they are all in common?  As the sun goes down the voltage goes down and when it gets below the battery voltage my Victron solar charge controller shuts off until voltage increases when the sun comes up. 

RV / Marine Battery Charging - Solar & Shore Power Combined! (https://roadslesstraveled.us/charging-rv-marine-batteries-solar-power-shore-power/#overview)
It can be done, I have my solar and smart chargers set up for same bulk. absorb and float voltages, so have no problem running ac chargers, and solar chargers at same time. But not all solar controllers have this ability, or even some smart inverter/chargers. I do have my engine alternator set at 13.6 volts, [thu combiner] so it basically only supply small float charge. It is not really precise, because when I use my ac charger, solar will go into float then shut off pretty quickly, but this is okay, because ac charger will supply 125 amps if necessary. But only using two solar controllers, have found both will charge at their max until very close to end of absorption. At this point not critical which one supplies float charge.
I did read your posts several years ago, so closely monitored both solar controllers  for a long time before I felt comfortable running everything together.

Mixed 335 and 280 watt panels.  Now I have 1187 watts, up from previous 560 watts.
 
I am using 4 LG panels with two 280 w panels installed two years ago at one end wired in series at one end and two LG 335 w panels at the other end wired in series, both groups to combiner box on roof in parallel and down refrig vent to single mppt charge controller rated at 1400 watts for a 12 volt system, 100 amp/150 volt rating.

I choose one solar controller over two separate controllers because of reduced cost and the fact I could then use all the existing wiring without any additional wiring.  By doubling the voltage down the refrig opening, existing wire was fine.  Two controllers would have only yielded  43 more watts on the roof, 1230 vs 1182 watts.

The math was as follows.  Max power of 335 watt panels 34.1 (max power volt, VMPP) x 2 = 68.2 V x 9.83 (max power current, MPP) = 770 watts.  LG 280 31.9 volt x 2 = 63.8 v x 8.78 = 560 watts.  In parallel 63.8 volts (lower of two parallel voltages) x 18.61 amps (combined amps) = 1187.31 watts from my roof system.

Mounting hardware, wire, and combiner box were all from AM Solarin Springfield, Oregon.

The calculations came from this source.
Mixing solar panels – Dos and Don'ts • SOLAR PANEL SECRETS EXPOSED (https://solarpanelsvenue.com/mixing-solar-panels/)

Bought last LG panel from Ecodirect. LG Solar 335 Watt Black Frame NeON 2 Solar Panel, Cello technology - LG335N1C-V5 (http://www.ecodirect.com/LG-Solar-LG335N1C-V-335-Watt-Black-Frame-NeON-2-p/lg335n1c-v5.htm)

Since we installed our four 285 watt Yingli panels ten years ago along with the controller, etc, the efficiency today has increased so with the same sized 36 volt panels, the output is now 345 watts in the YL345P-35b series. I also did a series/parallel installation so the voltage down to the controller is typically 72 volts. On freezing mornings, the voltage may exceed 80 volts just before the sun breaks the horizon so glad I took the advice from the controller manufacturer and didn't go all series. It would be nice to add more but since they are 1960mm / 992mm / 40mm and weigh just short of 70 lbs each, we just don't have any more room up top.

Just came back from camping where we met Craneman and his five panel system. On his mobil app, I could see that he is able to easily exceed 1000 watts even at our approx latitude of 38 degrees. He has a residential fridge while we have a Norcold RV fridge so our power requirement is much lower. At this latitude, we max at about 700 watts.

Right now, the controller is on float, supplying about 13.3V to the 3 conventional engine batteries and 6 AGM house batteries.

Controller is a Midnite 150 Best MPPT Charge Controller (2019) - Solar Charge Controller Reviews (https://mozaw.com/best-mppt-charge-controller/)

Pierce

Ours peaked at 1133 watts and 6.1 kwh's one day last month at June lake.

Neither one of our installations tilts the panels. Flat on the roof. With about 1.75 inches of clearance between the aluminum frame and the roof, the roof stays cool with the blue panel glass quite hot. While we were at June Lake, the sun was about 15 degrees from being directly overhead. Tilting panels can make quite a bit of difference but we don't need the extra watts. Next step will be to replace the OEM inverter to make everything more efficient.

Pierce