Solar. For Simpletons

[chubby]

Hello ,

 

I ve spent a few hours reading thru past posts on solar panel installations and i 'm now more confused than when i started . I'm sure its all very straightforward but the amount of technical jargon & terms just goes over my head . So if anyone can help me with my installation i ' d be very grateful but would ask in advance that such technical terms be kept to a minimum if possible because I just get lost in it all .

Ok . I have 4 x 100 w solar panels and this evening I ll be ordering a 40 amp Tracer MPPT controller , 4 mm cable & some MC4 connectors .

 

Can anyone advise how these are best connected .In series , or parallel & why one way is preferable to the other ? Will i need more connectors if connecting in Parallel ?

Once the cables are brought thru into the engine room ( hopefully thru a mushroom vent ) . I ' m sure its simple to connect these cables TO the mppt but where i get spun out is regarding connections between the mppt & the batteries , fuses & what type of cable is used to link the mppt & the batteries .

 

I ' m very sorry if this is basic stuff , but to me , as with just about everything on my boat its borderline rocket science . So if anyone can assist i 'd be very grateful . If more info from me is needed then i'll do my best to provide answers ,

 

cheers

 

Edit to add : i was hoping to get someone in to do this but unfortunately had no luck , so i 'll have a crack at it myself . cheers again

Edited March 21, 2014 by chubby

[Paul C]

What's the open circuit voltage of the solar panels, and what's the max input voltage for your controller? That's the thing which will determine if you can connect all 4 panels in series, or whether you need 2 "strings" of 2 panels, ie [2 panels in series] connected in parallel with the other [2 panels in series].

 

You only need MC4 connectors if its outdoors you make the connections, so if you are making the parallel connection outside, you'd need a Y adapter. If inside, then you could use something else. I'd suggest 2 runs of wire to the MPPT controller to minimise voltage drops.

 

MPPT controller --> cable --> inline fuse --> domestic battery bank (after the isolation switch) same terminal as the main feed, alternator, etc (all inputs and outputs to a battery bank should be from the same terminal).

[chubby]

Cheers ,

 

ok if Voc = open circuit voltage then on the rear of the panel it says 21.84 v . I hope this is helpful .

Which type of cable from mppt - fuse please ?

 

EDA : the max input for the mppt ( tracer 40 amp is 520 watts IIRC ) . I shall check & amend this if incorrect ,

 

cheers

Edited March 21, 2014 by chubby

[Paul C]

You'll be okay then with wiring all 4 panels in series, because the max input voltage on a 40A Tracer MPPT controller is 100V (according to a quick google search on the specifications).

 

I personally used 10mm2 cable for the run from the MPPT controller to the battery +12V side, and connected the negative to the negative bus bar on the fusebox which is mounted next to my MPPT controller, figuring that the negative always remains connected and the existing cabling here was sufficiently "fat".

[chubby]

Cheers .

So ishall look on ebay for 10 mm sq cable for the positive connections . After that , as i expected , i m lost . The electrics cupboard on my boat is a mess - at least to me anyway so as for the negative connection i shall have a mooch in the cupboard tomorrow afternoon . A bus bar ? i shall google this too ( i am a total novice at 12 v electrics )

Would i be right to believe that the in line fuse rating will be in the mppt instructions ?

Can the negative connection after the mppt go to a battery terminal itself like the positive ?

cheers again

[Nautihamstern]

You might want to make sure that your connectors to the controller are properly protected against accidental touch (IP 20 classification) since a voltage of 80 volts is potentially lethal.

[MtB]

You might want to make sure that your connectors to the controller are properly protected against accidental touch (IP 20 classification) since a voltage of 80 volts is potentially lethal.

 

Especially as it's DC.

 

The reason we use AC for higher voltage applications is because 100 times a second it passes through zero. This gives multiple opportunities for an electrocution victim to let go of the wire, unlike a victim of DC. The DC keeps the muscles continuously in spasm preventing letting go, so I understand.

 

This might be an urban myth though...

 

MtB

[tree monkey]

 

Especially as it's DC.

 

The reason we use AC for higher voltage applications is because 100 times a second it passes through zero. This gives multiple opportunities for an electrocution victim to let go of the wire, unlike a victim of DC. The DC keeps the muscles continuously in spasm preventing letting go, so I understand.

 

This might be an urban myth though...

 

MtB

we were warned about this when doing our track safety ticket for work on the railways, dire warnings about coming into contact with the 3rd rail, i think 750v dc, although i could very well be wrong about the voltage its definitely dc

[Clifford]

Chubby, You’ll need the same thickness cable from the controller negative connection to the negative bus bar (if you have such a luxury).

 

If it's not clear, a bus bar is as fat strip of metal with several screw connections along it, so several wires can be connected together in a way that looks nice (and doesn't set fire to your boat).