12v inline diodes for solar panels

[Ric]

I have four small 12v Solara flexible solar panels in parallel feeding into a Rutland HRDX regulator (also fed with a Rutland 913).

The problem with my current set up is that if one of the panels is in shade, it eats up charge from the sunbathing panels. I would like to fit inline diodes from each panel to improve efficiency.

I have googled for 12v diodes, but all I turn up are diodes suitable for mounting on PCBs. Are there no simple to mount inline diodes - like one-way chocolate box connectors?

 

[VicS]

I have four small 12v Solara flexible solar panels in parallel feeding into a Rutland HRDX regulator (also fed with a Rutland 913).

The problem with my current set up is that if one of the panels is in shade, it eats up charge from the sunbathing panels. I would like to fit inline diodes from each panel to improve efficiency.

I have googled for 12v diodes, but all I turn up are diodes suitable for mounting on PCBs. Are there no simple to mount inline diodes - like one-way chocolate box connectors?

If chocolate box connections is the way you want to go use two blocks for each diode. Connect the diode to one side of the box and the wires to the other.

Can't get them into the terminal boxes i suppose

Consider using Schottky diodes to minimise volts drop.
It may not be necessary but I'd use diodes rated a bit more than just 12 volts PIV... the panels develop over 20 v with no load.

 

[Ric]

Thanks - that seems the way to go.

 

[RestlessL]

The latest Rutland controller (HRDi) requires diodes for all solar panels (The HRDx does not need one if there is only 1 panel).

I use IN5820's

http://www.maplin.co.uk/3a-schottky-barrier-rectifiers-46409

As Vic says, they can be wired into 1 side of a choc block.

J

 

[BERT T]

The simplest way would be to use normal diodes, bend one leg into a U shape and put a piece of sleeving on it and push the two ends into a strip connector then connect the wires to the solar cell into the other side of the terminals. Mount the assembly inside a weatherproof box and that should solve your problem.

 

[CreakyDecks]

You can get bridge rectifiers with spade connectors. They also have a convenient hole for mounting. You would need two and would only be using two of the four diodes in each but they are pretty cheap.

 

[VicS]

You can get bridge rectifiers with spade connectors. They also have a convenient hole for mounting. You would need two and would only be using two of the four diodes in each but they are pretty cheap.

You cant access the diodes separately.

I dont think your idea is possible ... but perhaps I am missing something .. you'd better post a wiring diagram

 

[CreakyDecks]

You don't need to. Two of the diodes are "wired" the way you need and the other two will be reverse biased and can be ignored.

 

[noelex]

I have four small 12v Solara flexible solar panels in parallel feeding into a Rutland HRDX regulator (also fed with a Rutland 913).

The problem with my current set up is that if one of the panels is in shade, it eats up charge from the sunbathing panels. I would like to fit inline diodes from each panel to improve efficiency.

I have googled for 12v diodes, but all I turn up are diodes suitable for mounting on PCBs. Are there no simple to mount inline diodes - like one-way chocolate box connectors?

Solar panels in deep shade develop very high resistance. That is why blocking diodes do little and are often not fitted. If you conect the solar panel to a battery in the dark it will give you an idea of current drawn by the worst case of a shaded panel. The current drawn will be very small. The diodes you are proposing to fit will cost more power than they will save.

In series connection bypass diodes can be very beneficial, but this is not relevant to your parellel connection.

 

[VicS]

You don't need to. Two of the diodes are "wired" the way you need and the other two will be reverse biased and can be ignored.

I see what you mean ... I hope the OP can figure it out too.

A diagram would explain it.

 

[nigelmercier]

Consider using Schottky diodes to minimise volts drop.
It may not be necessary but I'd use diodes rated a bit more than just 12 volts PIV... the panels develop over 20 v with no load.

I agree about Schottky diodes, but I'm not convinced the OP has found 12V PIV diodes, I think they may be zeners - tip: don't search for 12V diode, like 12V LED, it doesn't mean anything.

I suggest something like this.

 

[William_H]

I have four small 12v Solara flexible solar panels in parallel feeding into a Rutland HRDX regulator (also fed with a Rutland 913).

The problem with my current set up is that if one of the panels is in shade, it eats up charge from the sunbathing panels. I would like to fit inline diodes from each panel to improve efficiency.

I have googled for 12v diodes, but all I turn up are diodes suitable for mounting on PCBs. Are there no simple to mount inline diodes - like one-way chocolate box connectors?

I find it surprising that the panels in the shade eat up the current. I would suggest that OP actually check with an amp meter to confirm this actually happens. I would have thought a panel in shade would still generate enough voltage to stop current flowing back. I have checked panels in the dark without a diode and while there is some reverse current it is not much.
Generally silicon or schotky diodes have a minimum of 200 volt PIV rating so usually voltage rating is not a concern. The rating is the voltage when applied backwards when the smoke escapes from the diode and it goes to diode heaven. It is the current rating that matters and even then small solar panels don't generate much current (.5 amp for 10w.) Schotky diodes will waste less power but this may not result in much difference anyway. good luck olewill

 

[ex-Gladys]

I have Solara panels, and they are each connected to a "cell protector" box supplied with the panel. I have two 45w panels on the wheelhouse roof, paralleled then connected to a Morningstar regulator. Channel where Gladys is moored runs (near enough) E-W, so the "average" is that one panel is shaded by the boom at all times. By the end of a couple of days just sitting, the domestics (3x100 AH AGM) are sitting reading 14.2V, and so obviously fully charged, and often the reading from the panels themselves is somewhere between 16 and 20V, so I find it difficult to understand the OP's experience...

 

[Ric]

Went down the boat today and checked current from each panel. There is indeed a small reverse current going into shaded panels. Diodes ordered!

 

[VicS]

Went down the boat today and checked current from each panel. There is indeed a small reverse current going into shaded panels. Diodes ordered!

Thanks for reporting that..... its valuable information.

What didoes are you buying?

 

[Ric]

I bought IN8520 3A Schottky bridge rectifier diodes, as recommended by Restless

I noticed after placing the order that my biggest panel has a max rated current of 3.6A. Is this going to be an issue?

Should I simply not attach a diode to the biggest panel on the grounds that it has the highest open circuit voltage, so is probably unlikely to suffer from backcharging, even when partially shaded?

Or will a 3A diode be robust enough to withstand the odd occasions when peak current is reached?

Or can I just attach two diodes in parallel? I know parallel diodes are unlikely to share the current identically, but can I assume that they will cope with an occasional 3.6A burst?

 

[cimo]

Went down the boat today and checked current from each panel. There is indeed a small reverse current going into shaded panels. Diodes ordered!

perhaps more valuable would be your current measurements Ric.
see post #9

 

[nigelmercier]

I bought IN8520 3A Schottky bridge rectifier diodes, as recommended by Restless

Not big enough, which is why I suggested 10A ones, and gave you a link.

No, you can't put them in parallel ... well you can, but it won't divide the current equally.

 

[VicS]

I bought IN8520 3A Schottky bridge rectifier diodes, as recommended by Restless

I noticed after placing the order that my biggest panel has a max rated current of 3.6A. Is this going to be an issue?

Should I simply not attach a diode to the biggest panel on the grounds that it has the highest open circuit voltage, so is probably unlikely to suffer from backcharging, even when partially shaded?

Or will a 3A diode be robust enough to withstand the odd occasions when peak current is reached?

Or can I just attach two diodes in parallel? I know parallel diodes are unlikely to share the current identically, but can I assume that they will cope with an occasional 3.6A burst?[/QUOTE]

IN8520 ?? you mean I assume 1N5820.. and they are discrete wire ended diodes not bridge rectifiers

You say you are using an HRDX cotroller and also a Rutland 913

I have only just noticed that the instructions for the HRDX do actually say

The HRDX controller is provided with a built in blocking diode to allow direct
connection of maximum 100w solar array. If the array is made up of modules in
parallel then each module should be fitted with it’s own blocking diode.​

It is therefore correct to fit each panel with its own blocking diode.

The diode my well withstand the occasional overload but they are so cheap I think I'd fit two in parallel for the largest panel.

 

[Ric]

Yes, I happened to re-read the instructions for my HRDX when I noticed that too. Hence my original question.

It does seem I have been losing a bit of efficiency over the years. The parasite currents were not big - 100-200mA approx, but they would add up over time. Certainly worth spending a few euros on diodes.