mppt controller

[noelex]

You may be obliged to wire panels in series to keep the power but reduce the current.

This usually does not help.
The MPPT maximum current rating usually applies to both the input and the output current.
Connecting the panels in series so the input is say 60v at 6A does not help because the output will be 14v at say a bit less than 25A.
So you need a 25A controller exactly the same as what you would need if the panels were in parallel. (but note you also need a controller if you connect in series that will cope with +60v, make sure you have some reserve with the voltage the controller will often be instantly damaged if this is exceeded)

 

[charles_reed]

1.Yes parallel is fine and arguably the best way. There is no need for any extra diodes

2. You need a controller which is OK with an input voltage of about 25v (this will be virtually all regulators). The maximum current is a bit under 12A with a MPPT regulator slightly less for a non MPPT regulator, but 10A is too small which means it will probably have to be a 15A model.

I'd tend to disagree with your first point (as a generalisation). Better by far to feed your MPPT unit with high volts and low current, than vice versa. Apart from wiring weights needing to be greater, the high input amps are going to tax the internals of the MPPT unit far more. As a final benefit you get (dependent on the MPPT unit) higher input voltages to the batteries and thus more effective charging.
However I would cede the point that local shading is likely to prove more degrading to series panels rather than ones in parallel.

 

[sailinglegend420]

......However I would cede the point that local shading is likely to prove more degrading to series panels rather than ones in parallel.

All sailboats will have some shading so parallel can often be a better solution if the cables are large enough. Not all panels are the same so ones with more bypass diodes may work better in series. I suggest everyone tries both parallel and series to see what works best for their installation.

 

[gianenrico]

Quote.
Dual model rated at 20A + remote display (more or less gives me what a Nasa BM1 would give) at something less than 100€; 2 X100 Watt panels in parallel.

 

[noelex]

I'd tend to disagree with your first point (as a generalisation). Better by far to feed your MPPT unit with high volts and low current, than vice versa. Apart from wiring weights needing to be greater, the high input amps are going to tax the internals of the MPPT unit far more. As a final benefit you get (dependent on the MPPT unit) higher input voltages to the batteries and thus more effective charging.
However I would cede the point that local shading is likely to prove more degrading to series panels rather than ones in parallel.

There is still considerable debate about the best connection for solar panels on boats. Seems a simple question and you would think we have a simple answer by now, but the reality is that is not the case.
The mathematical modelling of series and parallel with some shading (which is where the differences lie) is complex and practical experiments have not been conclusive.

My personal feeling is that parallel connection will produce the greater output, but I am happy to be convinced otherwise.

I am not sure there is less stress on the controller with series connection. As a mentioned in a previous post the output current will be identical with either type of connection. Series connection demands a greater voltage conversion from the controller and most are less efficient at these higher input voltages, so presumably generate a bit more heat. In any case the effect is very minor and I don't think it should be a factor.

The higher input voltage of series connection does not translate to higher output voltages to the batteries. The battery charging voltages are identical.

 

[charles_reed]

There is still considerable debate about the best connection for solar panels on boats. Seems a simple question and you would think we have a simple answer by now, but the reality is that is not the case.
The mathematical modelling of series and parallel with some shading (which is where the differences lie) is complex and practical experiments have not been conclusive.

My personal feeling is that parallel connection will produce the greater output, but I am happy to be convinced otherwise.

I am not sure there is less stress on the controller with series connection. As a mentioned in a previous post the output current will be identical with either type of connection. Series connection demands a greater voltage conversion from the controller and most are less efficient at these higher input voltages, so presumably generate a bit more heat. In any case the effect is very minor and I don't think it should be a factor.

The higher input voltage of series connection does not translate to higher output voltages to the batteries. The battery charging voltages are identical.

I tried both ways, all parallel and in 3 x 2 on a BZ 250. That's optimised for a 48v nominal input and copes with <72volts. It appears to put in marginally more at the higher 24 voltage during a 24 hour period and certainly results in a higher input voltages than when all the panels were in parallel. That's using the on-board voltmeter and ammeter for the readings.
It may be more a function of that MPPT controller and, one could argue, that each set of panels should have its own controller.

 

[William_H]

I am not sure there is less stress on the controller with series connection. As a mentioned in a previous post the output current will be identical with either type of connection. Series connection demands a greater voltage conversion from the controller and most are less efficient at these higher input voltages, so presumably generate a bit more heat. In any case the effect is very minor and I don't think it should be a factor.

The higher input voltage of series connection does not translate to higher output voltages to the batteries. The battery charging voltages are identical.

I am not sure you are right about higher voltage being less efficient when transformed down to 12volts compared to lower voltage. If you consider that your small power supply for your computer or so many other gadgets not to mention modern battery chargers work on the same principal but start with around 340v DC from rectified mains and they don't suffer from inefficiencies. olewill

 

[Tony Cross]

I tried both ways, all parallel and in 3 x 2 on a BZ 250. That's optimised for a 48v nominal input and copes with <72volts. It appears to put in marginally more at the higher 24 voltage during a 24 hour period and certainly results in a higher input voltages than when all the panels were in parallel. That's using the on-board voltmeter and ammeter for the readings.
It may be more a function of that MPPT controller and, one could argue, that each set of panels should have its own controller.

Certainly my experience of trying series and parallel with an MPPT controller was that in series (which is how they are now) the controller would easily get the battery charging voltage up to 14.4v but with them in parallel I never saw 14.4v at the batteries.

 

[nigelmercier]

Certainly my experience of trying series and parallel with an MPPT controller was that in series (which is how they are now) the controller would easily get the battery charging voltage up to 14.4v but with them in parallel I never saw 14.4v at the batteries.

This could be because you don't have enough individual cells in your panel.

 

[Tony Cross]

This could be because you don't have enough individual cells in your panel.

I have no idea, all I do know is that the batteries are maintained better with the panels in series. But that might well be because of some weakness in my setup. Either way I'm happy.

 

[noelex]

I am not sure you are right about higher voltage being less efficient when transformed down to 12volts compared to lower voltage. If you consider that your small power supply for your computer or so many other gadgets not to mention modern battery chargers work on the same principal but start with around 340v DC from rectified mains and they don't suffer from inefficiencies. olewill

You will notice the small power supply for your computer gets warm. That heat has to come from somewhere.
The efficiency of solar controllers (at least for the better models) can be found in the specifications.
The efficiency is higher when the input and output voltages are closer.
This is the graph from the outback controller.
It is not a big factor in the overall output of the solar panels. The shade performance difference between series and parallel are the more important factors