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solar wiring - is this right?


waterdog

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1 minute ago, Mike the Boilerman said:

 

Well one of us has! I took the breaker to be for isolating the panels from the MPPT. 

 

If it is, it's too small really, but in practice solar panels never deliver full rated output as perfect optimum conditions never occur, so the panel current will never *quite* reach 10A. 

 

 

 

 

His schematic showed the 63a breaker between the panels and the MPPT, and then the 10a breaker between the MPPT and the batteries.

 

 

solar wiring (1).pdf

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1 minute ago, Alan de Enfield said:

His schematic showed the 63a breaker between the panels and the MPPT, and then the 10a breaker between the MPPT and the batteries.

 

 

solar wiring (1).pdf 53.35 kB · 1 download

 

Ah. First time I've seen that diagram. Previous postings fail to display on my Mac.

 

Breakers are obviously the wrong way around in the diagram. 

 

 

And both wrongly rated, in my opinion. 

 

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57 minutes ago, Alan de Enfield said:

Agreed.

 

(I thought I was going even further along the madness scale)

 

20 amp Panels to MPPT

50 amp MPPT to battery.

 

 

 

Yes those values look about right to me too. 

 

Don't worry about moving up the madness scale though. I'll see you when you get here, up at the end. 

 

 

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3 hours ago, Mike the Boilerman said:

 

But it isn't 307W at 12V is it? Its 307W at 30V approx, typically. So that's 10A peak current, near as dammit. 

its going to be 60 volts at 614 watts I thought? 2 panels in series Mike

I have 16 amp MCBs between the panels and the controller with no issues at all and I have a lot more solar

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1 hour ago, Tony Brooks said:

I think 305 watts at 60 volts approx because they are in series. In series the amps stay the same as one but the  voltage doubles. That still gives less than 10 amps between panel and controller.

1 hour ago, Tony Brooks said:

 

image.jpeg.9c37e374d81037271c53bda4b86e9d8d.jpeg
Watts, Volts and AMPS. There are two ways to wire up Solar Panels. ... Solar Panels are usually connected in series to obtain higher output voltage. This is usually the case with 24v systems.
Wiring in series does increase the watts however if you are connecting different wattage panels its better to connect in parallel this article explains better
Edited by peterboat
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Watts is watts. Two panels, add the power (ie watts), irrespective of whether they’re in series or parallel. So two 300W panels will give a nominal 600W. In series that’ll be say 60V, so 10A. In parallel that’ll be 30V, so 20A.  It’s still 600W. Feeding the battery on the other side of the controller it’s still 600W but now at around 14V, so around 40A. 

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Morning All, I'm getting there with the installation, thanks for all your help so far.

 

I'm about to make the final connections at the batteries and I've got another question, where is the best place to make the connection for the positive from the controller,

 

1, straight to the batteries or live side of the isolator so panels will still maintain battery level if boat is left.

Or

2. To the "off" side of the isolator so the panels are disconnected when the boat gets left for longer periods.

 

3. Return (negative) connections to the shunt ?

 

Thanks.

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37 minutes ago, waterdog said:

2. To the "off" side of the isolator so the panels are disconnected when the boat gets left for longer periods.

If you do this your MPPT controller will 'explode' as it will have leccy going in but nowhere for it to go.

 

You do know never to disconnect the solar from the battery without 1st disconnecting the solar from the MPPT don't you ?

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15 minutes ago, Alan de Enfield said:

If you do this your MPPT controller will 'explode' as it will have leccy going in but nowhere for it to go.

 

You do know never to disconnect the solar from the battery without 1st disconnecting the solar from the MPPT don't you ?

Thanks Alan, yes I have fitted isolating breakers between the panels and the mppt. Reading other threads on here this appears to be prudent providing I remember to isolate the panels first before doing anything else. 

 

For clarity, are you saying it is best practice to have the mppt wired so it is permanently connected to the batteries?

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30 minutes ago, waterdog said:

For clarity, are you saying it is best practice to have the mppt wired so it is permanently connected to the batteries?

Yes. Why would you not want to charge the batteries for free whenever possible?

 

Don't forget to fuse the cable. 

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59 minutes ago, waterdog said:

For clarity, are you saying it is best practice to have the mppt wired so it is permanently connected to the batteries?

Yes - with a suitable fuse as close to the batteries as practical,

 

(It is allowed in the BSS regs as one of the few things that can be connected directly to the batteries.)

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54 minutes ago, WotEver said:

Yes. Why would you not want to charge the batteries for free whenever possible?

 

Don't forget to fuse the cable. 

 

24 minutes ago, Alan de Enfield said:

Yes - with a suitable fuse as close to the batteries as practical,

 

(It is allowed in the BSS regs as one of the few things that can be connected directly to the batteries.)

Thank you guys. I have all the wiring completed including fuse up to the batteries, just the connection from the fuse to battery and the neg to connect. 

 

I may have misunderstood the warnings about making sure the panels are the last things to connect otherwise magic smoke is produced but......

What if the battery fuse blows at any point with the panels "live", won't this create the same effect ? Or have I got this completely wrong.

 

P.S. The panels are still isolated via the breakers ?

Edited by waterdog
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1 hour ago, waterdog said:

What if the battery fuse blows at any point with the panels "live", won't this create the same effect ?

Yes - but like being unable to recover your anchor that you deployed to stop you going over the weir and dying - the fuse 'blows' for a significant reason and saved your wiring catching fire, your battery exploding due to a short and you getting sprayed in acid or burnt to death as the boat catches fire.

 

I may have exaggerated slightly, but if the fuse blows it will be because of a serious fault and your panels (anchor) should be the last thing to worry about. The fuse has done its job.

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It works, ? controller is indicating a charge and agreeing with the battery monitor that was already fitted and NO MAGIC SMOKE ????

 

Just need to understand what all the different numbers mean lol.

 

Huge thanks to all who have helped, ???

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17 hours ago, Alan de Enfield said:

Yes - but like being unable to recover your anchor that you deployed to stop you going over the weir and dying - the fuse 'blows' for a significant reason and saved your wiring catching fire, your battery exploding due to a short and you getting sprayed in acid or burnt to death as the boat catches fire.

 

I may have exaggerated slightly, but if the fuse blows it will be because of a serious fault and your panels (anchor) should be the last thing to worry about. The fuse has done its job.

 

Also good practice to replace fuses every 5 years, because the do occasionally fail due to old age and thermal stresses, rather than fault current.

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