Solar: Panels, controller

[Yellowjacket]

(1) Installing 3 X 360 watt solar panels on arch. May install two on house.
Nominal Power 360 W
Rated Voltage 59.1 V
Rated Current 6.09 A
Open-Circuit Voltage 69.5 V
Short-Circuit Current 6.48 A

(2) Ignorant of many things electrical, but understand solar shading, value of
MPPT, wire gauge vs voltage drop.

(3) 12 volt system; Batteries = about 900 amp/hours;

(4) Some panels will feed currently owned Victron Blue Solar 100 / 50:
Rated charge current 50A
Nominal PV power, 12V: 700W
Maximum PV open circuit voltage: 100V
Max. PV short circuit current: 60A
Maximum efficiency 98% 98%

(A) Is wiring even two panels in series is out of the question, given that this would create voltage higher than Victron limits? Three paenels on arch will have similar solar exposure. Could I run all three in parallel to Victron about 20 feet of wire?

(B) Given that Victron "reads" battery state from simple positive and negative connections to house bank or bus bar, how does it compensate for loads from house panel, refrigerator, etc, AND for contributions from other panel controllers connected to the same bus bar? Is there a possibility of overcharging or undercharging when other loads are present? Or does controller just see the net difference and provide current at a voltage that will work for that net sum total?

(C) Refrigeration draws directly off buss bar, does not go through main circuit breaker panel, and is not read by house amp meter. Amp meter I installed directly on battery indicates about a 25 amp draw for refer (has fuse). Is this OK?

(D) I anticipate needing at least one more MPPT controller, possibly two, because of differences in panel location, shading, etc. I assume I can connect to same location on bus bar as existing controller (bus bar in engine room is closest location to panels and MPPT; #4 cable (as big as my little finger) connects bus bar to battery bank. Sealed bulkhead makes running cable directly to battey difficult). Is this OK?

Thank you all for advice and direction. As to why so much solar: Panels were not too expensive; redundancy; Installation locations already in place (dinghy arch, canvas dodger/bimini) where they will not destroy lines of the boat; I'd like enough juice to run refrigeration, autopilot, radar, watermaker, etc. Genset is old, heavy, cranky (like owner). Would like to exchange for newer technology, perhaps additional power (owner needs same).

[sailormed]

I have a Morningstar MPPT controller. You can throw more voltage at it then its rating without damage. So you could put 2 panels in series to the Victron. Also because you only get the max voltage under optimal conditions, something you will never get in real life.

[john61ct]

Never say never.

Very common in cold reflective conditions.

[noelex 77]

Originally Posted by sailormed

I have a Morningstar MPPT controller. You can throw more voltage at it then its rating without damage. So you could put 2 panels in series to the Victron. Also because you only get the max voltage under optimal conditions, something you will never get in real life.

Perhaps the Morningstar is different, but I suspect you are thinking about current, not voltage.

For most controllers if you exceed their maximum voltage, even briefly, the magic smoke escapes, and of course without the magic smoke the controller will not work .

The Voc can, and likely will, be exceeded sooner or later in real life so most controllers recommend the controller is rated 10% or more above Voc.

[noelex 77]

Originally Posted by Erik Dolson

(A) Is wiring even two panels in series is out of the question, given that this would create voltage higher than Victron limits? Three paenels on arch will have similar solar exposure. Could I run all three in parallel to Victron about 20 feet of wire?

The 50A rating is for the output, as well as the input. Therefore on a 12v system the most power the controller will deliver is 50A at the charging voltage so about 700w. Your three panels total 1080w.

Series connection will permanently damage the controller. Parallel connection will not damage anything, but you will be wasting a lot of power so you need a bigger controller, or use multiple controllers, one for each panel.

Originally Posted by Erik Dolson

(B) Given that Victron "reads" battery state from simple positive and negative connections to house bank or bus bar, how does it compensate for loads from house panel, refrigerator, etc, AND for contributions from other panel controllers connected to the same bus bar? Is there a possibility of overcharging or undercharging when other loads are present? Or does controller just see the net difference and provide current at a voltage that will work for that net sum total?.

This will not be a problem.

Originally Posted by Erik Dolson

(C) Refrigeration draws directly off buss bar, does not go through main circuit breaker panel, and is not read by house amp meter. Amp meter I installed directly on battery indicates about a 25 amp draw for refer (has fuse). Is this OK?.

Yes

Originally Posted by Erik Dolson

(D) I anticipate needing at least one more MPPT controller, possibly two, because of differences in panel location, shading, etc. I assume I can connect to same location on bus bar as existing controller (bus bar in engine room is closest location to panels and MPPT; #4 cable (as big as my little finger) connects bus bar to battery bank. Sealed bulkhead makes running cable directly to battey difficult). Is this OK?

Yes,this is all OK, although the Victron controllers have an anoying feature that will occasionally result in the controller dropping prematurely to float when multiple charge sources are present.

Make sure you disable the temperature compensation and apply the correction manually, if the controller is in a different location to the batteries.

[smac999]

Originally Posted by sailormed

I have a Morningstar MPPT controller. You can throw more voltage at it then its rating without damage. So you could put 2 panels in series to the Victron. Also because you only get the max voltage under optimal conditions, something you will never get in real life.

This is totally wrong. You will get peak power voltage under most conditions. That is what the mppt controller does. You will get less watts and current under less ideal conditions. Higher voltage will blow up your controller. Some will take higher watts or amps. Without damage. However they just cut off and you lose the excess power. Ideally you should have 1 controller for each panel if they are going to get shaded different from each other.

[motion30]

The techs at Outback told me I could put more amperage into the controller with no problem but if I put More Voltage than its rated for it would generate the Magic Smoke

[john61ct]

Yes also the case with Victron.

75/15 I would not go over 65Voc panels, but can go over the 220W rating even up to 300W

Such overpanelling discards peak power moments but increases the average output per SC.

[Yellowjacket]

Noelex 77, smac999, everyone, thank you very much. This is a huge help.
I put a volt/amp meter on the panels just to check for a bad one, and on October 27 near the 45 parallel at 1:30 p.m., voltage read 69.1 to 69.7 on the five panels, and over 60 volts with one corner of the panel, about six cells, shaded. I think it would be very easy to exceed rating on the Victron by a substantial margin.

Nolex, you said that reading the voltage off buss bar serving different loads at the same time would not be a problem for the Victron. Would you mind educating me why these loads, positive or negative, do not confuse the unit? I'd assumed it could not know where the juice was coming from.

It would appear my tendency (it's a character flaw, nothing to be done about it at this stage) of being excessive (if I can afford it or find it if I can't) will result in having a separate controller for each of the five panels, eventually. I'm designing a fairly simple and robust way to angle panels to the sun after my experience with a single panel. It makes a huge difference in solar gain. All panels will not benefit simultaneously, however, so the different outputs would otherwise decrease the ability of MPPT to maximize efficiency.

Victrons have the ability to communicate to each other, but that's more research I've not yet done.

Are there thoughts about a quality, 12 volt watermaker capable of 300+ gal./day? Am I being foolish (yes, it happens, more often than what's left of my self-esteem after buying a boat will admit) in trying to abandon the 3 KW Balmar genset from 1994?

BTW, half-inch v-belt will NOT drive a 160 amp alternator, no matter HOW many times you adjust or replace the belt. And it's called Mastervolt because you need a masters degree to read the documentation. I don't have one. And why don't they put a flow arrow on a Jabsco water pump for a gen set, or at least make the seals out of unobtainium?

Thank you all again. Cruisers Forum is invaluable.

~ Erik

[Yellowjacket]

By the way, a quick glance around a marina indicates that about half the solar panel installations run a ground wire from the frame to the ground system of the boat. I would have thought that would be a safety issue. No? Perhpas it's buried where I can't see it.

[seandepagnier]

Originally Posted by Erik Dolson

(A) Is wiring even two panels in series is out of the question, given that this would create voltage higher than Victron limits? Three paenels on arch will have similar solar exposure. Could I run all three in parallel to Victron about 20 feet of wire?

It may not be a good idea to run the panels in series because of partial shade to a single panel. The bypass diodes may bypass an entire panel if it is partially shaded. This loses that entire panel as well as wastes some power in the diode.

If the panels were in parallel, you would still get some output from partial shaded panel. It is also somewhat less efficient to convert the voltage down if the voltage difference is greater as well. Ideally you have separate controllers for each panel, but even without you get better shade tolerance in parallel configurations.

On a roof top partial shade is not usually a concern, so you can save a lot of copper, and if you are inverting to higher voltages it makes even more sense too.

(C) Refrigeration draws directly off buss bar, does not go through main circuit breaker panel, and is not read by house amp meter. Amp meter I installed directly on battery indicates about a 25 amp draw for refer (has fuse). Is this OK?

Not sure of your wiring, but I recommended to run the controller output directly to the battery rather than sharing existing power wires. This is because if the battery becomes disconnected (wire corrodes or rat eats it) then you can easily get voltages much higher than normal battery voltages in your system. This will damage some but not all electrical stuff if you have say 20 volts or so.

Originally Posted by Erik Dolson

By the way, a quick glance around a marina indicates that about half the solar panel installations run a ground wire from the frame to the ground system of the boat. I would have thought that would be a safety issue. No? Perhpas it's buried where I can't see it.

Does it have something to do with static discharge? Can you ask these people?

[Nicholson58]

Originally Posted by noelex 77

Perhaps the Morningstar is different, but I suspect you are thinking about current, not voltage.

For most controllers if you exceed their maximum voltage, even briefly, the magic smoke escapes, and of course without the magic smoke the controller will not work .

The Voc can, and likely will, be exceeded sooner or later in real life so most controllers recommend the controller is rated 10% or more above Voc.

In the tropics, we frequently get more than the rated panel output. I would not exceed the MPPT rating. Also, I suggest all panels parallel. There is always shading from the rigging, even just a stay can knock down output.

[Yellowjacket]

Originally Posted by Nicholson58

In the tropics, we frequently get more than the rated panel output. I would not exceed the MPPT rating. Also, I suggest all panels parallel. There is always shading from the rigging, even just a stay can knock down output.

Different panel locations, different shadings at different times. Wouldn't running all panels parallel guarantee less than optimum performance for all panels ALL the time, instead of less than optimum just for the shaded panel?

[noelex 77]

Originally Posted by Erik Dolson

Nolex, you said that reading the voltage off buss bar serving different loads at the same time would not be a problem for the Victron. Would you mind educating me why these loads, positive or negative, do not confuse the unit? I'd assumed it could not know where the juice was coming from.

The solar controller’s battery algorithm is only interested in voltage. The current (or juice) does not play a role.

So at each stage of charging the solar controller is simply trying to keep the voltage at an appropriate value.

For example, in the absorption phase the set point might be 14.6v. The solar controller is trying to keep its output voltage at 14.6v. At one SOC the battery might be accepting 10A to stay at this voltage. So with no load the solar controller will deliver 10A to maintain the 14.6v.

If a load such as a fridge is turned on drawing 8A, the voltage will drop, but the solar controller will sense the voltage is no longer 14.6v and will very rapidly allow more current from the solar panels (assuming they can supply this) until the voltage stabilises again at 14.6v. To do this it will be supplying 18A. The battery will still be at 14.6v and receiving 10A so the load makes no difference.

The only slight problem is the voltage drop in the wiring. We want to keep the battery at 14.6v, but for most solar controllers they can only measure their output voltage. Ideally the solar controller would be mounted very close to the batteries, but this is often not practical. If the wiring is an appropriate size, a more remote location, as you are planning, is not a great problem especially as the solar input tends to offset the load in the wiring, so the current carried by the wires is not high.

Some sophisticated controllers will measure the voltage at the actual battery. Victron make an accessory to do this. It has some technical limitations although it may also help with the annoying problem of tail current cut off that Victron have programmed into their controllers.

It is worth checking the actual charging voltage at the battery. This helps compensate for errors in the controller’s voltage sensing allows manual temperature compensation, and some allowance for a typical voltage drop can be allowed for, although the latter will not be a constant number. The very fine voltage adjustment of the Victron units (0.01v) is a great help with this.

[Nicholson58]

Originally Posted by Erik Dolson

Different panel locations, different shadings at different times. Wouldn't running all panels parallel guarantee less than optimum performance for all panels ALL the time, instead of less than optimum just for the shaded panel?

PARALLEL only the shaded panel drops out. The shadow of a shroud is enough to drop panel output drastically

SERIES. All panels drop out at a shadow.