Series or Parallel Panels?

[goboatingnow]

I faced the same issues with two 180 watt panels with a nominal Vmp of 19v , with temperature effects this could drop 2V or more , this meant my victron smart controller would not activate till the sun was high in the sky wasting valuable charge time

In the end I went with a PWM controller. The loss of the MPP was much less then the issue as described above

[sailcrazy]

Following. Our 4-80 watt panels are connected in parallel, to a Victron MPPT Controller. Maybe age, or a little shading, or??, but the output in pretty minimal.

[Jon Hacking]

Pretty much everyone here is assuming 36-cell (12v nominal) panels. And folks are correct that with high temperatures, especially if the panels don't have good air-flow around them, panel voltages sag, sometimes to the point of not having enough voltage over the battery voltage to drive the MPPT.

FWIW, we've found that bigger, more powerful panels offer better performance ($/W). In 2001, our 120W Kyocera panels cost $4/W. The 400W Powitt panels we bought in the Philippines in Dec 2019 only cost $200, or 1/8th the cost ($0.50/W), for monocrystalline glass panels, guaranteed for 12 years (parts & materials) & 30 years performance. So folks might want to think about upgrading their panels.

These bigger panels (& they're 1x2m) are 72-cell panels, nominally 24v but with Vmp (max-power) at 40v & Voc (open-circuit) at 48v. These have no problems driving an MPPT to charge 12v (or even a 24v) systems.

Of course, a 72-cell panel is really just 2x36-cell panels in series. Shading a single cell doesn't shut down the whole panel, but it does knock down its output noticeably. Shading a single cell in a 36-cell panel will usually knock its voltage down to where the MPPT can't then charge a 12v battery, but with 72-cell panels (or 2x36-cell panels in series) you still get significant power out, even with shaded cells. Ours are mounted above the davits, & (mostly) behind the boom, so we don't have serious shading issues unless we're underway.

FWIW, we tied the grounds of all 3 panels together, but the positives we ran each to its own MPPT. We used 8ga wiring (I think) as it's 30' as the wire crawls from my panels to my batteries.

[Adelie]

I would put each panel on its own controller.

[RaymondR]

I have been the each panel on it's own regulator and found it to be expensive and involved a lot of wiring.

I notice on the LiPo battery where I am running the MPPT from 24V nominal that the amps going into the battery is a lot more than that coming from the battery which is what one would expect if the MPPT is working to both buck up and down from the panel voltages.

I'm beginning to feel a suspicion that wiring in series to feed a good quality MPPT controller may be the way to go.

[Nicholson58]

There will always be shading. Parallel and use big wire. I hope your panels have diode isolated circuits as well.

[thomm225]

Two PWM controllers 3-4 panels. Parallel and single. One panel has plugs the others I had to soldered on the wires

12-14 gauge wiring. Charging two 220 ah 6 volt Golf Cart Batteries in series.

Connection at battery: alligator battery clips which are disconnected for the weekend.

[tamicatana]

Connection at battery: alligator battery clips which are disconnected for the weekend.

What could go wrong?

[thomm225]

Originally Posted by tamicatana

What could go wrong?

That depends.

Not much right now, they are disconnected. Batteries are charged.

The clips that have been on there for the last 5-6 years are a bit rusty so that controller reads .1 volts lower than the new setup I did yesterday. New $15.00 controller, and new 14 gauge wire soldered on to new alligator clips.

That could be the old controller or the rust depending......

[tamicatana]

Well… ABYC ain’t in it, is there?

Your connection is not breakered/fused, it isn’t solid, and it sounds like your wiring may be undersized, although in your defense you did not elaborate how large your panels are.

If your alligator clips should happen to bounce off underway, you now have a dangerous short and likely fire.

Gat insurance?

[tamicatana]

Originally Posted by thomm225

That new 14 gauge wire soldered on to new alligator clips.

Should be a CRIMPED connection. Your rig is unsafe.

[thomm225]

Originally Posted by tamicatana

Should be a CRIMPED connection. Your rig is unsafe.

Crimped?

The wires are soldered.

[thomm225]

Originally Posted by tamicatana

Well… ABYC ain’t in it, is there?

Your connection is not breakered/fused, it isn’t solid, and it sounds like your wiring may be undersized, although in your defense you did not elaborate how large your panels are.

If your alligator clips should happen to bounce off underway, you now have a dangerous short and likely fire.

Gat insurance?

You have assumed a lot in a short time.

Wiring size is fine.

And my system is fused to the load.

20 watt panel 14 gauge wire. (soldered on by me)

65 watt panel 14 gauge wire (for the last 9 years soldered on by me)

50 watt Renogy with it's own wiring maybe 12 gauge.

20 watt panel hooked up direct to batteries.

I have sometimes all connected and sometimes none while at other times 1, 2, or 3 panels connected.

Panels are tied on so I can turn them toward the Sun or just laying on a lazarette locker.

The 20 watt panel has fallen off here.

https://www.youtube.com/watch?v=-nXfjcCuiPk

[tamicatana]

The standards, for those caring about safety:

ABYC Standards
Reprinted with permission by the American Boat & Yacht Council. This is not the full text of E-11 of the ABYC standards. It is in response to some of the most commonly asked questions.


The construction of insulated cables and conductors shall conform with the requirements of: 11.16.1.2.2.1. UL 1426, Cables for Boats…”11.16.1.2.2.”

"Conductors shall be at least 16 AWG. EXCEPTIONS: 1. 18 AWG conductors may be used if included with other conductors in a sheath and do not extend more than 30 inches (760mm) outside the sheath.” 11.16.1.1.2.

"Conductors shall have a minimum rating of 600 volts.” 11.16.1.3.3. “The temperature rating of conductors and flexible cords shall be at least 140ºF (60ºC) dry.” 11.16.1.3.1.

"In engine spaces, 11.16.1.3.4.1. the insulation shall be oil resistant, and 11.16.1.3.4.2. the temperature rating shall be at least 167ºF (75ºC) dry.” 11.16.1.3.4.

"Minimum surface marking of the individual conductors and their jackets shall include: 11.16.1.1.1.1. type/style, 11.16.1.1.1.2. voltage, 11.16.1.1.1.3. wire size, and 11.16.1.1.1.4. temperature rating, dry.” 11.16.1.1.1.

"All conductors and flexible cords shall meet the flame retardant and moisture resistant requirements of UL 83,Thermoplastic-Insulated Wires and Cables.” 11.16.1.3.5.

"Conductors used for panelboard or switchboard main feeders, bilge blowers, electronic equipment, navigation lights, and other circuits where voltage drop must be kept to a minimum, shall be sized for a voltage drop not to exceed three percent”. (See Table B)

Conductors used for lighting, other than navigation lights, and other circuits where voltage drop is not critical, shall be sized for a voltage drop not to exceed 10 percent.” 11.16.1.2.7. (See Table C)

"When AC and DC conductors are run together, the AC conductors shall be sheathed, bundled, or otherwise kept separate from the DC conductors.” 11.16.4.1.5.

"Wiring shall be installed in a manner that will avoid magnetic loops in the area of the compass and magnetically sensitive devices. Direct current wires that may create magnetic fields in this area shall run in twisted pairs.” 11.16.4.2.1.

"Current-carrying conductors shall be routed as high as practicable above the bilge water level and other areas where water may accumulate. If conductors must be routed in the bilge or other areas where water may accumulate, the connections shall be watertight.”11.16.4.1.6.

"Loom used to cover conductors shall be self-extinguishing. The base product (or resin) shall be classified as V-2 or better, in accordance with UL 94, Tests For Flammability Of Plastic Materials.” 11.16.4.1.9.

"Conductors shall be supported throughout their length or shall be secured at least every 18 inches (455mm) by one of the following methods:” 11.16.4.1.10.

"By means of non-metallic clamps sized to hold the conductors firmly in place. …The material shall be resistant to oil, gasoline, and water and shall not break or crack within a temperature range of -34°C (30°F) to 121°C (250°F);” 11.16.4.1.10.1.

"By means of metal clamps lined with an insulating material resistant to the effects of oil, gasoline, and water.” 11.16.4.1.10.3.

"Terminal connectors shall be the ring or captive spade types.” 11.16.3.4.

"Twist on connectors, i.e., wire nuts, shall not be used.” 11.16.3.6.

"Ring and captive spade type terminal connectors shall be the same nominal size as the stud.” 11.16.4.1.12.

"Solder shall not be the sole means of mechanical connection in any circuit.”11.16.3.7.

"Solderless crimp on connectors shall be attached with the type of crimping tools designed for the connector used, and that will produce a connection meeting the requirements of E-11.16.3.3.” 11.16.3.8.

"The shanks of terminals shall be protected against accidental shorting by the use of insulation barriers or sleeves, except for those used in grounding systems” 11.16.3.9.

"Conductors that may be exposed to physical damage shall be protected by self-draining; loom, conduit, tape, raceways, or other equivalent protection.” 11.16.4.1.8.

[dfelsent]

I’ve got three panels tied to three controllers. The wiring for each panel is separate.
As the shading moves around each panel / controller produces what it can.
Given the cost of a panel why not spring for the extra controller?
What you gain in efficiency you can save in panel size.