Multiple Solar Controllers????

[b_rodwell]

I have been told by some wise people that theoretically it is better to have a solar controller for each set of series solar panels. This is supposed to be better than one big controller.

• How does that work?
• Do you need to have a controller-of-the-controllers?
• How much do the controller-of-the-controllers cost?
• How do they work?
• Why is it better?
• More generally is it possible to get a master controller that handles all the inputs and all the outputs?

Please enlighten me?

Cheers,

Brian

[dksail]

If you have several solar panels that are never obstructed or shaded, even just a small part of one panel, then you can use just one solar controller. If you think any one of the panels will be shaded for some reason, it will impact all of your other panels as the system will always look for the lowest voltage.

So, if you have shading, separate your panels into small groups and provide a separate solar controller for each group. This will ensure that you get the most energy out of your panels.

Most new controllers these days, certainly from Victron and others, the MPPT controllers will talk to each other. No master controller is needed. They are almost all bluetooth enabled so you can monitor each one. If you would like, you can buy gadgets that will combine the displays on on one device, but it is not needed.

[noelex 77]

Hi Brian

The advantage of multiple solar controllers, ideally one controller per panel, is that the input voltage can exactly match the particular panel. When multiple panels are connected to a single controller the controller must select an input voltage that is a compromise between the two panels. Multiple controllers also create valuable redundancy.

If the solar panels are exposed to the same conditions, this input voltage compromise is generally very close to the ideal, but when different conditions such as shadows fall on just one panel, the resulting maximum power point can be very different between the panels. In these cases the resulting compromise may produce significantly less power than optimising the power point for each panel seperately. This is only possible with multiple controllers.

The drawback of multiple controllers is a higher parasitic consumption and greater wiring complexity. As well, there can be occasional conflicts with the charging algorithm of more than one controller. This latter problem is minor and some solar controllers allow for linking eliminating this concern. On the popular Victron Smartsolar range this synchronisation is particularly easy.

[smac999]

One per panel is best. Otherwise any shading on any panel effects them all. No series panels unless none of the whole set can not shade. (Or all shade together in a set)

On a house with no trees around one controller is fine as non will ever shade.

[b_rodwell]

Query comments about panels in series???

Context:
A number of sets of panels in series
Partial shading randomly distributed across sets
One controller per set of panels but controllers talk to each other

Why is this a problem?

Cheers

Brian

[CaptainRivet]

Originally Posted by smac999

One per panel is best. Otherwise any shading on any panel effects them all. No series panels unless none of the whole set can not shade. (Or all shade together in a set)

On a house with no trees around one controller is fine as non will ever shade.

Totally wrong If the panels are connected in parallel and that’s what you do on a boat. If one gets shade all the others still output all they produce.
if you take LG neon 2 panels with 12 bus bars technology only the row that get shade shuts off but rest of the panel still delivers.
If your array of panels is in the same roughly +/- 3V range (so eg 19V-25V) you can connect the array to 1 big and high quality(!) MPPT controller with negligible loss to each with its own controller...but if you take the added cabling to all the controllers into mind these cable losses add up and you end up with less performance then 1 big one plus costs and effort for cables...
MPPT means multi point power tracking, so the Controller can sort the different voltages of the panels. Only PWM the panel with lowest voltage defines the array, MPPT you can and will have even different voltages with identical panels.

The higher the voltage the more you can put several panels in an array on one MPPT, eg. a 40 and 50V panel works fine.

Several controller can interfere with each other when not communicating with each other and sending the data via Bluetooth doesn’t mean the other controller takes that into account. Victron,as far as I know the only one, creates a BT VE network where the controllers really talk to each oth and take parameters in account.

I nearly killed my bank having 3 MPPT interfere which each other, overvoltage was set to 14,6V but it reached 21V and only then shut off. Only overvoltage on 13.9V cured it temporarily to reach 14.3V but with poor performance.

Only 2 Victron 50/100 BT smart controller cured it permanently. 2 because too much for one and 2nd the ridget LG panels 710W array runs on 38V while flexible 680W sunpower array on 19V (17V to 22V,different panels)..too much apart to use one controller

To decide what to use:
Mounting Location and roughly same panel voltage define what to use. Common is ridget panel on davits or Reling one controller and semi flexible on Bimini or pilothouse on another one. All panels connected parallel. Controller as close to battery as possible.

[goboatingnow]

I put my two panels in series better use of modern mppt controllers and battery wiring

[noelex 77]

Originally Posted by CaptainRivet

I nearly killed my bank having 3 MPPT interfere which each other, overvoltage was set to 14,6V but it reached 21V and only then shut off.

There are a couple of threads on solar controllers at the moment, so apologies for the duplication:

There are some minor conflicts caused by using multiple solar controllers, but the effect is minimal. The popular Victon Smartsolar controllers (and some other brands) can be synchronised to eliminate these issues.

It is not likely your 21v battery voltage was caused by any conflict. If both controllers are programmed to stop the charging at 14.6v, this is what they will do (if functioning correctly) whether you have one controller or many. This is not dependent on syncronisationation.

[CaptainRivet]

Originally Posted by noelex 77

There are a couple of threads on solar controllers at the moment, so apologies for the duplication:

There are some minor conflicts caused by using multiple solar controllers, but the effect is minimal. The popular Victon Smartsolar controllers (and some other brands) can be synchronised to eliminate these issues.

It is not likely your 21v battery voltage was caused by any conflict. If both controllers are programmed to stop the charging at 14.6v, this is what they will do (if functioning correctly) whether you have one controller or many. This is not dependent on syncronisationation.

Well they were programmed correctly, all identical to 14,6V but only shut off when at 21V....I needed to put 13.9V overvoltage so at the bank 14,3V reached...each shuts of at 13.9V but at the BMS 712 That resulted in 14.3V....14.3V overvoltage 14.7V at BMS, 14,6V results in 20V..strange but that was 1000% interference between these controllers ( 2 were the SilentWind controller, the MPPT solar part), I could replicate it.
Have victrons now and synchronized, problem solved.

[CaptainRivet]

Originally Posted by goboatingnow

I put my two panels in series better use of modern mppt controllers and battery wiring

Yes and if one gets shade, quite common on a mono, you have nothing....the best MPPT cannot do anything here.
In parallel one delivers, one is in shade and delivers less =>MPPT can sort that.

[CaptainRivet]

Originally Posted by b_rodwell

Query comments about panels in series???

Context:
A number of sets of panels in series
Partial shading randomly distributed across sets
One controller per set of panels but controllers talk to each other

Why is this a problem?

Cheers

Brian

Brain, it’s very simple. In Series one shaded panel takes out all panels wired in series to it. It’s like a water Hose, put 2 after each other and block one, no water. Now connect them in parallel and block one...still water, a Bit less

[goboatingnow]

I have 2 180w panels wired in parallel it’s hard to get much use from a mppt controller as with the higher temperatures the Vmp begins to move down towards the battery voltage.

With serial the mppt has more headroom

Would parallel still be better

[Dsanduril]

Originally Posted by CaptainRivet

...MPPT means multi point power tracking, so the Controller can sort the different voltages of the panels. Only PWM the panel with lowest voltage defines the array, MPPT you can and will have even different voltages with identical panels...

The "M" in MPPT stands for Maximum Power Point Tracking. It indicates that the controller can find the maximum point at which to produce power. It does this by selecting a single voltage point for all the panels/strings connected to it (unless it is a multi-input MPPT, which is a whole other beast). If you put a 24V panel in parallel with a 48V panel into a single MPPT controller it will not be able to sort that out. Depending on panel sizes it will make one of two decisions:

1. Operate at 24V - in which case you lose ~50% of the output from your 48V panel
2. Operate at 48V - in which case you lose 100% of the output from your 24V panel (it will just sit there, unable to push electrons because it doesn't have enough oomph).

This is why individual controllers are recommended. Even with identical panels, if one panel is in full sun (at say 48V), and the other is shaded such that one bypass diode is activated (so the voltage is 36V) then each controller will operate at the maximum point for that individual panel.

[tanglewood]

Originally Posted by CaptainRivet

Brain, it’s very simple. In Series one shaded panel takes out all panels wired in series to it. It’s like a water Hose, put 2 after each other and block one, no water. Now connect them in parallel and block one...still water, a Bit less

I don't think this is correct. If you lose one panel you halve the voltage, but current remains the same. Provided the remaining voltage is above battery voltage and the minimum required by the MPPT controller, you should get 1/2 output.

[Jack1112]

Solar panel is connected to my 16 year old 700 amp RV batteries through a "Renogy Wanderer Li 30A 12V" that couldn't power the RV lights overnight. after bulk charge and 2 days of float charge lights will stay on for a couple of days , when camping the panel is connected to the batteries so they are fully charger all day, I have the panel laying flat on the RV roof, I could get an inverted and bring a blender camping, but were camping . very pleased with the performance of the panel and charger.