Cable size for three panels

[asdex]

Hi, just wanted to check my maths. I have three panels:
IMP 4.33A, VMP 17.3V. If I run in parallel to charge a 12 volt system I would have 12.99 amps and need to size the cable from panels to controller for this current?
Thanks,

[Logan5]

Distance of the run?

[Logan5]

MPPT charge controller?

[asdex]

Distance is 10 meters and it is a MPPT charge controller. Its actually a Lorentz pump controller which runs directly from the panels.I think it can use any voltage as long as its less than 50 volts.
Thanks,

[Logan5]

30 feet is a short run, If you place all three panels in series would exceed 50v , You could easily use AWG10 even with a lil lower voltage. This is part of a pump system? 12 volts is an inefficient voltage for pumping, Many can also run from a 24 volt bank. check again your MPPT pump controllers Max. input voltage and well as the voltage expectations of the pump. I would make sure of these before proceeding.

[Sunking]

33 feet is a very long distance and is going to cost you a lot of money running those panels in parallel.

Example if you used 10 AWG copper at 33 feet one-way, 13 amps, 17 volts results in an unacceptable 7% loss in voltage and power. The goal is 7% total from panels to Battery Term Post. That is 3 circuits for a total of 7%. You blew your budget on the first cable run. The 3 circuits are:

Panels to Controller 2% or less
Controller 3% fixed loss
Controller to Batteries.2% pr less

Total 7% maximum.

Assuming 3% fixed for the Controller which you have no control over only leaves you 4% for the other two legs of the circuit to work with

You want 2% from Panels to Controller. If you wire it your way will require 4 AWG about the size of you thumb. If you had a real MPPT Charge Controller, wired the panels in series would only require very small and cheap # 14 AWG.

In the USA #14 AWG cost 7-cents per foot, so 70 feet cost less than $5. 70 feet o #4 AWG cost 85-cents per foot or roughly $60. You chose the most expensive option there is and does not buy you anything.

Good luck.

[Logan5]

If your pump controller can do it's job and use a separate better quality MPPT charge controller, that allows 100+ Iinput voltage, you could use the smaller gauge wire. Sunking is correct if you are stuck in the 12 volt box, it's going to cost you.

[asdex]

Thanks, I'll check with the supplier. You can run off batteries as well but I would need another charge controller. I have a PWM one I could use a Prostar 15 but it could be a bit small as max motor current is 18 amps.

[asdex]

Seems I'll need a charge controller to run off batteries. The pump controller only has one input. Batteries or PV.
I'm wondering about only using two panels in series rather than three in parallel.
As well as small cable, the higher voltage may be more efficient than the higher current lower voltage.
I'm also just checking with the supplier what controller to motor size cable I would need If I mount the controller at the PV panels and run motor cable the 10 meters. They have supplied 6 meters of 4mm 4 core as the pump is 3 phase.

[Mike90250]

What is the make/model of the pump. Major brands, we can look up the specs on the web. Most solar PV pumps are quite flexible.

[asdex]

Hi, thanks for your comment.
The pump is a Lorentz P150 Boost-60. It comes with its own MPPT controller PS150-UL
I'm pumping up to our cabin which is a 90 meter lift.
Cheers,

[Sunking]

Have you read the specs and noted the Graph? Tells you everything you need to know.

You start with the graph to find the required wattage panel. Some wattage between 10 and 220 watts. You then select a panel with a minimum Vmp = 17, and maximum Voc = 50 volts. It is made to be ran on a Solar Panel alone.

Only trick is to buy the right size panel. There is a line in Panel Wattage that defines a Battery Panel, and Grid Tied Panel. That wattage is roughly 160 to 190 watts. Anything less will likely be a 36 cell Battery Panels But a battery panel Vmp runs 16 to 18 volts. You must have 17 volts or more. Panels 200 watts and up are higher voltage grid tied panels. All of them will be greater than 17 volts.

OK you have 3 battery panels which was a mistake. 3 is a PRIME NUMBER and is going to bite you in the Arse. You know what that means? You can only configure your panels either all in series, or all in parallel. Here is the fun part, you only have one option with your 3 panels, all IN PARALLEL. 3 in series would exceed the controller's 50 Voc limit. Even two could be to much on cold mornings. With a Voc limit of 50 volts, once you derate for temps as 40 volts would be the design limit. I bet your panel Voc is 22 volts and two in series is 44 volts.

So you really have one or two options open to you. Pick your poison. The pump was designed in mind for using one properly sized panel with or without a battery. If you want a battery, size it for 8 Ah for every 10 watts of panel. But had better have a good control, because with battery will run until th ebattery dies and makes a flood.

[Logan5]

You need a better solar pump controller, likely a whole new package pump and controller set up. Is this a new pump or old equipment? Working with old outdated equipment will cost you more than a new more efficient higher voltage set up.

[asdex]

Hi Sunking, thanks for that information. I didn't know about the panel types.
These three panels were originally on the cabin when we bought it charging a 12 volt system. I installed new panels and run a 24 volt system now. So these panels are just spares.
It looks like I will connect them in parallel as I don't want any chance of exceeding the 50 volt max.
About the prime number and arse biting, I'm not actually sure what you mean? I think you saying I'm stuck with buying the expensive cable as the panels in parallel will be producing a higher current.
If that's so, it still cheaper to buy the heavy cable than a new panel I expect.
I hope the voltage will be high enough though to run the pump.

[asdex]

You need a better solar pump controller, likely a whole new package pump and controller set up. Is this a new pump or old equipment? Working with old outdated equipment will cost you more than a new more efficient higher voltage set up.

This is a brand new setup. $2500 worth for pump and controller. Lorentz is a Germany company and I think their gear is good quality.