Cable size for three panels

[asdex]

I have looked at the graph and if I add a few meters for the tank it looks like I need a 150w panel and as you mentioned a Vmp greater than 17 volts and a Voc less than 50 volts plus take into account for cold. Does the Voc take into account cold weather when the voltage can be higher of you you need to allow for that?
Thanks,

[Logan5]

Indeed, I just went to their site and they do make very nice quality pumps. Not sure why they did not incorporate higher voltage panels into their design. Voltage input limits requires larger wire size for your panel run. I like that it is battery free. what is your pumps planned head? is this a well? submersible or a surface pump? what is the model number?

[asdex]

The head will be around 100 meters. It will pump from a creek via two settling drums and a filter so its a surface pump.
Its the P150 Boost-60. I see there is a controller option with PV in and battery in, the PV charging the batteries. I only have the PV in or battery in model.
I may yet buy a new PV panel and just use a long cable from PV controller to motor. This is the recommended way as in the instructions it mentions placing the controller away from the PV panels can be more susceptible to lightning voltages.
I'm just waiting to hear back from the supplier about replacing the 6 meter motor cable for a 10 meter one. Should solve most of my problems.

[Sunking]

Asdex keep this in mind. The minimum Vmp that controller can handle is 17 volts at its input. That is not good news for you. Most 36-cell battery panels have a Vmp of 16 to 18 volts. Now here is the bad news. If your panels Vmp is 16 to 17 volts, not going to work because you have no voltage to work with. You will have voltage loss between panels and controller. No way around that.

Here is where it gets really ugly. If your panels are 17.3 volts, you have almost nothing to work with. Extremely difficult and expensive to work with a 0.3 volt window over 10 meters with 13 amps. Understand? Now if this was say a 200 watts 50-cell or more panel, no problems at all because now Vmp is up to 25 volts and leaves you 8 volts to work with.

If I were you I would look for other options.

1. Sell/trade your 3 panels for a single 200 to 250 watt panel.
2. Bight the bullet and just buy a single 200 to 250 watt panel.

Think of this; using the 3 panels you have now is going to cost you at least $100 to $150 just for the wire, Odds are it will not work, or work poorly. Not exactly sure what a 200 to 250 watt panel will cost you in your area. My guess is $200 to $400, but only requires $15 to $20 of wire and guaranteed to work.

Put it to you this way. If you were to hire me to do this and insisted I use your panels. I would tell you to find someone else to do the work. I would not want my name associated with it.

Take that FWIW

[asdex]

Hi Sunking, looks like you are absolutely correct. I'll purchase a 250 watt panel.
Is the Voc value the highest voltage a panel can produce or can it go above this when very cold? eg can I use the Voc figure as a maximum or is it guesswork as to the highest voltage a panel will output.
I don't expect there to be a problem, I see 250 watt panels are around 36-38 volts so with voltage drop there is still a big margin before the 50 volt limit.
Thanks,

[asdex]

A 250w panel that looks like it will do the job is about NZ$270

Suntellite
ZDNY250P60
250watt
Vm 30.76v
Im 8.13A
Voc 37.75v
Isc 8.55A
60 cells

[Sunking]

A 250w panel that looks like it will do the job is about NZ$270

Suntellite
ZDNY250P60
250watt
Vm 30.76v
Im 8.13A
Voc 37.75v
Isc 8.55A
60 cells

Perfect. With 8 amps, 30 meters, Vmp = 30 volts requires:

!0 AWG for a 2.1% voltage loss. FWIW if the distance was say 2 meters only requires 14 AWG for 0.3% loss.