Series or parallel for solar

[bespin]

Hi just a quick question we have 4x100w panels on our boat 12v each and an mppt regulator which is the best way to wire the panels in series or in parallel for the highest amps out.

 

Thanks

[Higgs]

Hi just a quick question we have 4x100w panels on our boat 12v each and an mppt regulator which is the best way to wire the panels in series or in parallel for the highest amps out.

 

Thanks

 

You're going to need them fitting in parallel to maintain your 12v. The amps will be the combined amp output of all four.

 

There should be a label on the underside of the panels giving a rough idea of optimum output for a good sunny day. Can your regulator cope with all four panels. Without looking at mine (3x100w), I think they are rated at about 8amp (3x8amp=24amp). My regulator is rated at 20 amp, so, I'm going to feed one through the wind generator regulator, which has a solar panel input connection.

Edited March 30, 2013 by Higgs

[GoodGurl]

yep what he said

[Chris Pink]

Hi just a quick question we have 4x100w panels on our boat 12v each and an mppt regulator which is the best way to wire the panels in series or in parallel for the highest amps out.

 

Thanks

 

You can fit them in series to the maximum input voltage of the MPPT - with a safety margin. 100W panels are likely to by 22VOC or so so 2 of them 45V - check in your MPPT manual, it is important the maximum voltage is not exceeded.

 

The advantage: smaller cables, the drawback: if one panel gets shaded all in that series string will stop.

 

I would keep them in parallel if the panels were reasonably close (4-5m) to the controller.

 

But if they were further away series (or 2 in series, 2 sets in parallel) would be a good thing, but take action to make sure the chances of them getting shaded are at a minimum (it doesn't take much shading to knock out the whole output of a panel)

 

The advice above is wrong, the MPPT controller manages the voltage to current conversion to the limit of its input voltage.

 

With a PWM controller you would need to keep them in parallel to keep the voltage near to the battery charging voltage.

[bespin]

Thanks chris and everyone they are currently at the max 5 metres from the controller and are not shaded the controller can handle 40 amps so should be enough also got an inline fuse to protect it. Will put them in parellel then and see how it goes thanks

[Chris Pink]

Thanks chris and everyone they are currently at the max 5 metres from the controller and are not shaded the controller can handle 40 amps so should be enough also got an inline fuse to protect it. Will put them in parellel then and see how it goes thanks

 

If you've still left the MC4 (or MC3) connectors on, it should be reasonably easy to do a few tests. I assume a Tracer MPPT, it would be interesting to see if there was any difference in output (theoretically there shouldn't be) at the different voltages.

 

Always assuming, of course, you can get a day of steady sunshine.

 

Slightly off-topic, shading is a bigger factor than it might appear. I had a 60W panel this morning with an area about 3" square in the shade the rest in bright sun at 30° or so. The output was 0. It's out the shade now, an hour later - so the sun is a bit higher - and the output is at 2A

[dor]

 

Slightly off-topic, shading is a bigger factor than it might appear. I had a 60W panel this morning with an area about 3" square in the shade the rest in bright sun at 30° or so. The output was 0. It's out the shade now, an hour later - so the sun is a bit higher - and the output is at 2A

 

I think people underestimate the effect of shading. You often see panels with a rope across or otherwise shaded. It's really worth getting an ammeter for the panel - only a few pounds on ebay - to see what your panel actually produces and when.

[smileypete]

Hi just a quick question we have 4x100w panels on our boat 12v each and an mppt regulator which is the best way to wire the panels in series or in parallel for the highest amps out.

Some of the smaller sized panels have 'bypass diodes' which makes shading much less of a problem when they're in a series string.

 

If the mppt is good for 100V or more, you could try them in series, shade one and see if the charge current to the batts drops to zero or not. If it only drops by up to 25% then the panels do have bypass diodes.

 

If you can post the make/model of the panel or a pic of inside the junction box, it might be possible to look up whether they have bypass diodes or not.

 

Wiring in series may only give a tiny bit more amps from the mppt but doesn't need extra MC3/MC4 splitters or junction boxes/cable glands.

 

cheers, Pete.

~smpt~

Edited March 31, 2013 by smileypete

[bespin]

Re read the tiny manual again and it says better in series. I will try the shading thing later see if it drops the mppt is a tracer so can do upto 120v I think the panels are from tri solar we were getting upto 20amps yesterday though not constant with them in series. I,do have the connectors so could try both just need a day when it's not cloudy. There is no shade on our mooring so series could be the way to go.

Edited April 1, 2013 by bespin

[peterboat]

Hi I havw half my panels in series and the other half in parallel one mppt controller on each bank. the in series mostly does better on amps. Not a lot admittedly but enough to make a difference throughout the day. Its true about the shading my chimberly does shade the panels at times and that does make a difference!!

 

Peter