Panel connections

[dapope]

I will be installing solar on our wobbly box in the next few weeks.
I have gone with 4x 350w solar panels feeding 2 panels into 2x pl40s.
My question is, as I am wiring parallel, can I daisy chain the panels ie connect one to the other then run one pair of wires to each pl40. Pos to pos and neg to neg. Assuming the panels are rated and sized, I should,d get around 35 amps a pair under normal conditions.

[T1 Terry]

I will be installing solar on our wobbly box in the next few weeks.
I have gone with 4x 350w solar panels feeding 2 panels into 2x pl40s.
My question is, as I am wiring parallel, can I daisy chain the panels ie connect one to the other then run one pair of wires to each pl40. Pos to pos and neg to neg. Assuming the panels are rated and sized, I should,d get around 35 amps a pair under normal conditions.

You will need to link the panel pr of 4mm sq cables to a length of 6B&S (13.5mmsq) for the run from the roof to the controller. The 2:1 cable joiners are just nonsense for a panel greater than about 60w if the run length is going to be greater than a mtr or so.
The average run from a roof top junction box to the controller is 5 mtrs, but up to 7 mtrs if the controller/battery is at the other end of the van.
Do you already have the PL40 controllers? What Vmp are the 350w panels and what voltage is the house battery?

T1 Terry

[dapope]

Yes, I have the pl40s.
I was going to use 6bs all the way, with andersons they are glass panels not semi flexible. I will post all the data on the panels when they arrive, but from memory they were 22v and about 18 amps out
200 ah of winstons for 12v

[T1 Terry]

Yes, I have the pl40s.
I was going to use 6bs all the way, with andersons they are glass panels not semi flexible. I will post all the data on the panels when they arrive, but from memory they were 22v and about 18 amps out
200 ah of winstons for 12v

Any reason for using the 2 x PL40 controllers? Or you just had them, so why not? Unusual to see panels of that capacity @ nom. 12v, generally they are rooftop solar panels much above 200w. The 18 amps output per panel will require 6 mm sq cable from the panel junction box to the neutral links in the rooftop connector box, either 4 busbars/neutral links (2 negative and 2 positive, one for each controller) and a separate run of 6 B&S to each 40 amp No Arc circuit breaker and then on to the PL40's
or
A Victron 150/100 MPPT controller @ around the $1200 mark, all 4 panels linked in series using 6mm sq cable, through a No Arc 40 amp circuit breaker and get roughly 10% more output, could be even better in poor solar conditions because of the huge solar area you have all linked in series so shade tolerance is optimised.
Yeah, I know, T1 praising the benefits of an MPPT controller The qualifiers are the very large solar array and the fact you can link them all in series.
The newest Victron Smart MPPT controllers have a networking facility so they can network with the Victron 712 BMV to get an accurate battery voltage, something that was not previously possible unless the controller had voltage sensing cables, combined with the VE direct remote on/off cable, it can be controlled by a number of high end BMS systems, including the latest Electrodacus SBMS0 and the T1 Lithium control system.
You could also use the MPP Solar 80 amp MPPT controller, it can handle up to 145v open circuit and an output of 80 amps, so it would clip a bit off the top in good solar conditions, but it is a lot cheaper than the Victron 150/100 .... These need a voltage boosting control system that fools the controller into seeing a higher battery voltage when the charging needs to stop, a bit complex to design and build and relies on the MPP Solar MPPT controller actually reading the sense voltage terminals .... after having a problem with a few controllers we moved over to the Victron units because we couldn't get any joy from the factory, or at least their local rep ....

T1 Terry

[jon_d]

A Victron 150/100 MPPT controller @ around the $1200 mark, all 4 panels linked in series using 6mm sq cable, through a No Arc 40 amp circuit breaker and get roughly 10% more output, could be even better in poor solar conditions because of the huge solar area you have all linked in series so shade tolerance is optimised.
Yeah, I know, T1 praising the benefits of an MPPT controller The qualifiers are the very large solar array and the fact you can link them all in series.

Fell off me chair.



Terry, the MPP controller (5048 from memory) generates a fair bit of noise in the DC_DC area. I have one and it took quite a lot of work to suppress it. The problem was the noise was getting into the shunt circuit area and affecting the SOC accuracy.

[T1 Terry]

A Victron 150/100 MPPT controller @ around the $1200 mark, all 4 panels linked in series using 6mm sq cable, through a No Arc 40 amp circuit breaker and get roughly 10% more output, could be even better in poor solar conditions because of the huge solar area you have all linked in series so shade tolerance is optimised.
Yeah, I know, T1 praising the benefits of an MPPT controller The qualifiers are the very large solar array and the fact you can link them all in series.

Fell off me chair.



Terry, the MPP controller (5048 from memory) generates a fair bit of noise in the DC_DC area. I have one and it took quite a lot of work to suppress it. The problem was the noise was getting into the shunt circuit area and affecting the SOC accuracy.

Thanks for that tip John, we hadn't experienced that problem before but we have had issues with the earlier MPP solar inverters with a built in PWM controller.
Just checked on their website and I really stuffed up, the MPPT controller is only 60 amps and called a PCM60X .... but the bit about the voltage sensing being a hit and miss affair and the local rep not being at all helpful still stands .....

T1 Terry

[dapope]

Thanks for that input.
The van is a poptop, already had 1 pl40, and a second one was relatively cheap. My plan was to use anderson plugs to have shorter leads on when the top is down. I will look at some heavy fuses within the circuit. I am planning to mount everything in the front boot.
I couldnt find an mppt controller on ebay that would manage what I was looking at that was reliable or a known brand, hence the pl40s.
I got another bmv 700 rather than the more expensive version. I dont need the bluetooth function. I just want to know the ins and outs. It was really about daisy chaining the panels so i can reduce wiring runs. Two sets of wires at the front of the van.
Not too worried about early morning output either. I reckon i should get 10 amps or so on a cloudy day, instead of the 70 or so on a fine day

[T1 Terry]

Better to use the No Arc DC circuit breakers so you have a switch to turn the solar off as well as a short circuit protection. Don't be tempted to use the cheap single cable circuit breakers with the lever and push button, usually black body and maroon lever and button. They are cheap for a reason, they are not very reliable, either false trip regularly or weld themselves closed so they can't be tripped.

T1 Terry

[Eddy]

Hi Terry - which brands of No Arc Dc circuit breakers have you found reliable ?
Thanks

[T1 Terry]

https://www.tro-pacific.com/collections ... gLup_D_BwE my bad, spelt the name wrong, Noark not No Arc ....

T1 Terry