Solar panels should each have their own controller?

webcraft

webcraft

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The guy on the boat next to me has just said each solar panel should have its own controller because if one is in shade and one is not the controller will not produce max available power from the non-shaded panel.

Is there any truth in this?

— W
 
webcraft said:
The guy on the boat next to me has just said each solar panel should have its own controller because if one is in shade and one is not the controller will not produce max available power from the non-shaded panel.

Is there any truth in this?

— W
Click to expand...
If you connect the panels in parallel he's totally wrong. If you connect them in series, he's correct.
 
Using multiple MPPT solar controllers will almost always result in a higher solar yield because the maximum power point voltage can be tracked, ideally, for each panel.

When multiple panels are connected to one controller it can only select the maximum point for the group of panels. If the panels are in disparate conditions, as often occurs on a boat, the maximum power point voltage may be significantly different between the panels.

Wiring the panels in parallel is usually better than series, but it does not solve the above problem

Multiple controllers also has the advantage of redundancy.

However, there are significant drawbacks which means it is not always the best overall solution. It is more complex and difficult to wire and often is more expensive (although in some cases, multiple solar controllers may be no more expensive than a single larger controller). With very small panels there can be issues where the self consumption of the multiple controllers defeats the gains.

It is important to realise the gains in solar yield from using multiple solar controllers is typically not large, but it is a common option adopted when the maximium yield for a given space is a priority.

The above only applies to MPPT controllers.
 
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Another option to consider is using multiple controllers, but not necessarily one per panel. For example, wiring two starboard panels to one controller and two port panels to another. This can sometimes be a sensible compromise.
 
Refueler said:
Given most boats of small to medium size are 12v (with odd smattering of 24v - I accept) ... but at 12V - parallel would be the usual way as panels are usually in the 18v ~ range ...
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Doesn't matter if you're using MPPT, you can use much higher panel voltages and it will convert them to the best voltage to charge your batteries.
 
@webcraft you've already got the controllers so just run with what you have. If you were starting from scratch there's an argument for separate controllers.
On our old boat we had 4*100w 12v panels on one controller, and 2*260w 32v on the other. All feeding the same 12v battery.
 
We have 8 panels going through 5 victron mppt controllers and then have a victron smart sense Bluetooth module connected to the battery bank. This means the controllers all work as one large one (as the smart sense chooses one of the controllers to control the others via the Bluetooth network they create). This results in better efficiency and also redundancy as on our previous boat we had a single large victron controller and it failed...no solar!
 
Refueler said:
Given most boats of small to medium size are 12v (with odd smattering of 24v - I accept) ... but at 12V - parallel would be the usual way as panels are usually in the 18v ~ range ...
Click to expand...
I'm not sure there is a "usual way".

Very often on sail boats there are significant shading issues, so parallel makes sense. But if, for instance, there are two panels on one side that don't individually suffer from shading, i'd be inclined to connect in series. I might have another pair on the other side, also in series, then connect the two sets in parallel, or more likely use two controllers. Series wiring also helps with cable sizes and voltage drop.
 
PaulRainbow said:
I'm not sure there is a "usual way".

Very often on sail boats there are significant shading issues, so parallel makes sense. But if, for instance, there are two panels on one side that don't individually suffer from shading, i'd be inclined to connect in series. I might have another pair on the other side, also in series, then connect the two sets in parallel, or more likely use two controllers. Series wiring also helps with cable sizes and voltage drop.
Click to expand...

But surely because panels voltage is fairly constant IF providing - its the amps that goes up / down with sun / shading etc ... in series can mean too high a voltage ? In case on most panels at ~18V .. that's 36V ..... ??
I could be wrong - have to dig out the instructions .. but aren't controllers limited to about max 25V ??
 
Refueler said:
But surely because panels voltage is fairly constant IF providing - its the amps that goes up / down with sun / shading etc ... in series can mean too high a voltage ? In case on most panels at ~18V .. that's 36V ..... ??
I could be wrong - have to dig out the instructions .. but aren't controllers limited to about max 25V ??
Click to expand...
If we're talking MPPT controllers, then the max voltage is one of the specifications that you select when you buy it. The Victron range come in both 75v and 100v for example.
 
Refueler said:
But surely because panels voltage is fairly constant IF providing - its the amps that goes up / down with sun / shading etc ... in series can mean too high a voltage ? In case on most panels at ~18V .. that's 36V ..... ??
I could be wrong - have to dig out the instructions .. but aren't controllers limited to about max 25V ??
Click to expand...
Mine is 150V
 
I think most Most MPPT controllers only "buck" the voltage. ie reduce with switching increasing current. (I may be wrong they may be able to boost input voltage. Specs don't specify min input voltage) But that means that a 20v panel must produce more than about 14v to get any charge in to a 12v LA battery. The panel will hopefully produce more than 14v in over cast or twilight conditions.
However 2 panels in series will produce between them 14v down from 40v in much more extreme low light conditions. Therefor producing some charge into the battery for less light. So series connection has it's value. ol'will
 
William_H said:
I think most Most MPPT controllers only "buck" the voltage. ie reduce with switching increasing current.
Click to expand...
Yes, that is correct. There are only a few MPPT controllers that will boost voltage.

William_H said:
I think most Most MPPT controllers only "buck" the voltage. ie reduce with switching increasing current. (I may be wrong they may be able to boost input voltage. Specs don't specify min input voltage) But that means that a 20v panel must produce more than about 14v to get any charge in to a 12v LA battery. The panel will hopefully produce more than 14v in over cast or twilight conditions.
Click to expand...
This is not usually an issue. Solar cells still produce a reasonably high voltage in low lighting conditions. There is a very slight gain in the length of time power is produced by increasing the solar panels’ voltage, but the extra energy is only slight. The performance in conditions with shade is more critical on a boat, and here parallel connection or one controller per panel is better than series connection. There are some exceptions when hooking up very low-voltage panels.
 
William_H said:
I think most Most MPPT controllers only "buck" the voltage. ie reduce with switching increasing current. (I may be wrong they may be able to boost input voltage. Specs don't specify min input voltage) But that means that a 20v panel must produce more than about 14v to get any charge in to a 12v LA battery. The panel will hopefully produce more than 14v in over cast or twilight conditions.
However 2 panels in series will produce between them 14v down from 40v in much more extreme low light conditions. Therefor producing some charge into the battery for less light. So series connection has it's value. ol'will
Click to expand...
Victron controllers need +5V above the battery voltage to start, so a 18V panel needs to be at 17V if the battery is at 12V before it even starts. So if there are no shading issues series can give a small gain here.
 
PaulRainbow said:
Victron controllers need +5V above the battery voltage to start, so a 18V panel needs to be at 17V if the battery is at 12V before it even starts. So if there are no shading issues series can give a small gain here.
Click to expand...
There are no "12V" panels with an open circuit voltage as low as 18V.
 
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