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Spoonman

Solar controller positive ground

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I am trying to install  solar panels and i have found a positive ground mppt solar controller online. The boat electrics are all 12 volt dc, no AC.

 

Assuming that my existing system is  negitively grounded as is usual,  Will the polarity of the ground in the mppt make a difference , provided i install it correctly? ( Positive terminal of controller  to positive terminal of battery). 

 

I have attached a picture of the "engine electrical system" given to me by the previous owner,can anyone confirm from this that it is indeed negitive ground.(sorry about the poor quality)

IMG-20200720-WA0000~2.jpg

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47 minutes ago, Spoonman said:

Assuming that my existing system is  negitively grounded as is usual, 

If you look at your batteries and see which terminal goes to 'ground' you should be able to determine if it is - or + earth.

 

It would be VERY unusual if it were + Earth

 

Why would you want to buy a + controller when there is a multitude of - controllers to choose from ?

If it is simply to try and save a 'few pennies' the resulting 'sparks and fire' will certainly cost more than you have saved.

Edited by Alan de Enfield
  • Haha 1

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Buy a negative earth solar controller.  Trying to make a positive earth one work with a negative earth boat will be very difficult, if not impossible.  Expect sparks and magic smoke escaping very early in the proceedings.

N

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That diagram is for a Lucas 10 for 11 AC alternator and in the early days many were positive ground.  However the batteries seem to be negative earth but with a relay to break the bod to the engine when the ignition is turned on so goodness knows what it is. As the parts for a 10/11 AC system must be getting like rocking horse dung AND they are low output machines I would suggest that before  the OP worries about solar they change the whole system to a 70 amp negative earth A127 with VSR to get a much simpler system, well understood conventional earthing. and a much higher alternate output.

 

There is a second "isolation" relay in the main starter supply. I suspect its to do with trying to make it insulated return.

 

I bet this is not a narrowboat, It also seems to have a B1,B2,Both, Off battery switch as well as a negative master switch, all very complicated.

 

Edited to add. After all this time I have doubts that the diagram has much resemblance to the present system. Photo of the alternator would help identify it.?

Edited by Tony Brooks

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Crazy over complicated wiring system, an antique. 4TR regs went out with Ford Pops.

As Tony said, change it to current standard first.

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1 minute ago, Tracy D'arth said:

Crazy over complicated wiring system, an antique. 4TR regs went out with Ford Pops.

As Tony said, change it to current standard first.

Thanks. I suspect it has already been changed. The alternator must have worn its brushes out since about 1970 and those awful 3AW warning lamp controllers were done away with well before the ACs were superseded by the ACRs.

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5 hours ago, Spoonman said:

I am trying to install  solar panels and i have found a positive ground mppt solar controller online. The boat electrics are all 12 volt dc, no AC.

 

Assuming that my existing system is  negitively grounded as is usual,  Will the polarity of the ground in the mppt make a difference , provided i install it correctly? ( Positive terminal of controller  to positive terminal of battery). 

 

I have attached a picture of the "engine electrical system" given to me by the previous owner,can anyone confirm from this that it is indeed negitive ground.(sorry about the poor quality)

IMG-20200720-WA0000~2.jpg

Most solar controllers are in plastic boxes, so the concept of a chassis ground doesn't really apply. What is fairly common is for the active circuitry to be in the negative side of the system, so that the positive wire from the solar panels is continuous through the controller to the positive output wire, and the magic happens in the negative, so the negative connection to the panels is NOT the same as the negative of the electrical system the controller is connected to. The only precaution you need to take is to treat both wires between the solar panels and the controller as "hot" and make sure they are well insulated from other cables and the hull of the boat. Don't connect the controller negative input terminal to battery negative under any circumstances. Most panels are designed to be used in series and have ridiculously high insulation between both terminals and the case, so there's not problem there.

 

TL;DR, connect as you describe, fuse the wire from battery positive to the controller. Treat both cables from the controller to the panel as needing good insulation, and it'll be fine.

 

MP.

 

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On 20/07/2020 at 11:45, Tony Brooks said:

That diagram is for a Lucas 10 for 11 AC alternator and in the early days many were positive ground.  However the batteries seem to be negative earth but with a relay to break the bod to the engine when the ignition is turned on so goodness knows what it is. As the parts for a 10/11 AC system must be getting like rocking horse dung AND they are low output machines I would suggest that before  the OP worries about solar they change the whole system to a 70 amp negative earth A127 with VSR to get a much simpler system, well understood conventional earthing. and a much higher alternate output.

 

There is a second "isolation" relay in the main starter supply. I suspect its to do with trying to make it insulated return.

 

I bet this is not a narrowboat, It also seems to have a B1,B2,Both, Off battery switch as well as a negative master switch, all very complicated.

 

Edited to add. After all this time I have doubts that the diagram has much resemblance to the present system. Photo of the alternator would help identify it.?

 

 

Thanks for the advice.You are right the alternator is an 11ac Lucas alternator. Surprisingly i removed it and the seperate regulator and had it tested separately and it was putting out a charging voltage so it maybe have been refurbished sometime between now and 1975😮

 

However i think the whole engine electrical system has not ever been upgraded. That diagram was done in 2013 by the previous owner! Everyone that has looked at it has just shaken their heads with bewilderment.

 

The engine is an sr2. Am i right in thinking that a 70- 80 amp alternator would be the limit to upgrading without major modifications. As you mentioned i have seen the ac127 suggested for this purpose before. Are the regulators intergrated in to this alternator or would a separate one still be required?

 

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10 minutes ago, Spoonman said:

 

 

Thanks for the advice.You are right the alternator is an 11ac Lucas alternator. Surprisingly i removed it and the seperate regulator and had it tested separately and it was putting out a charging voltage so it maybe have been refurbished sometime between now and 1975😮

 

However i think the whole engine electrical system has not ever been upgraded. That diagram was done in 2013 by the previous owner! Everyone that has looked at it has just shaken their heads with bewilderment.

 

The engine is an sr2. Am i right in thinking that a 70- 80 amp alternator would be the limit to upgrading without major modifications. As you mentioned i have seen the ac127 suggested for this purpose before. Are the regulators intergrated in to this alternator or would a separate one still be required?

 

The regulator is integral with the A127, the main charging lead(s) can be reused apart from the fact you will be potentially doubling the charging current. Depending upon exactly what A127 you get you may have to connect the main charging negative to the case/engine block rather than a main negative terminal. You will have to rewire the warning lamp but that is simple enough. Ing.Sw > lamp > Alt D+ terminal (don't wire it to the W rev counter terminal because it will no work but no damage will be done). you throw the AC regulator, relay & warning lamp control - if fitted - away.

 

If this is a canal boat I would simplify the whole system to make it negative earth with no extra relays and then fit a VSR instead of the 1,2,both, off switch so it does the charge splitting without the risk of human error.

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