Length of wires from PV panel-controller-battery?

[user 423]

My present solar setup has the battery located right under the controller at the rear of the van and the wires are just 2' long. The wires from the panel to the controller are about 7' long.

I want to move the battery 6' forward, just above the well of the side (barn) doors.

The controller can stay where it's at but then the wires to the battery will need to be 6' longer. Or I can move it forward 6' to be close to the battery but then the wires from the panel will need to be 6' longer (total length ~13').

Which would be the best location for the controller?

I'm using a Renogy 100 watt kit with one 31DC battery.

PS: I won't need to buy any more 10 ga. wire.

 

[highdesertranger]

under ideal conditions you want the wire runs as short as possible. but just as long as you pay attention to voltage drop and use the appropriate gauge wire you can mount the controller and batteries almost anywhere. the voltage coming from the panels is probably a little over 20v and the voltage coming out of the controller is close to 12v. so running longer wire from the panels to the controller you could get away with slightly smaller wire than from the controller to the battery. if you need help with the math give us the specs on the panels and the controller. highdesertranger

 

[user 423]

^
Okay, I have the RNG100D monocrystalline panel that's rated at 18.9V w/load.

The controller is a Wanderer 30A PWM.

All wires are 10 gauge.

 

[jonyjoe303]

With 6 feet your going to have voltage drop. I have over 1/2 volt drop with 4 feet. Since your using lead acid, 14.4 volts might end being 13.8 volts at battery terminals. After you got everything connected measure the voltage from controller and bounce that against the battery terminals.

Hopefully your controller bulk settings can be adjusted, increase the bulk voltage appropriately (maybe even as high as 15 volts) to get 14.4 volts at terminals. If the batteries never reach 14.4 volts and stay there for hours, they will be undercharged.

renogy settings need the bluetooth module to program

 

[DLTooley]

Two reasons to put the controller closer to the battery:

1. The controller regulates the voltage to the battery and will adjust for any voltage drop from the panels. This will improve your charging.

2. Better controllers adjust for temperature and having the controller next to the battery will also mean a more accurate charge.

Both of these factors have work arounds depending on the specifics of your controller
- charge profiles that can be customized for measured drop and remote temperature probes.

With ten gauge wire and heated interior mounting neither of these factors is huge. Quality of the wire splice matters and don’t put it in an inaccessible spot such as after a build

 

[Tom_M]

It's best to have the controller as close to the battery as possible. If the battery is a flooded lead acid it should be vented and the charge controller should be in a different compartment. Fumes from the battery can corrode wiring in the controller.

 

[user 423]

Hopefully your controller bulk settings can be adjusted, increase the bulk voltage appropriately (maybe even as high as 15 volts) to get 14.4 volts at terminals.

The controller is an older model and isn't adjustable.  No port for the BT module. I'll eventually upgrade to a MPPT.

The system is pretty basic and I'm in learning mode to see how long it takes to kill the battery..LOL.

I've used it for the past 8 months to power a small Alpicool fridge, to charge batteries and for light use of a laptop .

 

[user 423]

Two reasons to put the controller closer to the battery:

1. The controller regulates the voltage to the battery and will adjust for any voltage drop from the panels. 

2.  Better controllers adjust for temperature and having the controller next to the battery will also mean a more accurate charge. 

With ten gauge wire and heated interior mounting neither of these factors is huge.  Quality of the wire splice matters and don’t put it in an inaccessible spot such as after a build

A temp sensor was optional with this model and I may add one later. Or upgrade the controller.

Looks like I'll be moving the controller forward and close to the battery.

 

[user 423]

If the battery is a flooded lead acid it should be vented and the charge controller should be in a different compartment. Fumes from the battery can corrode wiring in the controller.

It is a flooded LA and it will be going into a vented box in a separate compartment from the controller.

I installed the setup last spring when I was in a hurry to hit the road. Now I've got some time to rearrange things and do a better job.

 

[user 423]

With 6 feet your going to have voltage drop. I have over 1/2 volt drop with 4 feet.

Finally got this done and ended up with the + wire being about 3-1/2 feet. 

The voltage drop is negligible. Less than .10 volt.

 

[highdesertranger]

thanks for the follow up. what gauge wire did you end up using? highdesertranger

 

[user 423]

^
10 gauge. No splices.