MAX length cable for solar panel?

[Randy]

Hey guys, one more question regarding my solar project this weekend. What is the max length I can use for a solar panel before I start loosing juice to the battery?

 

[smritte]

How much power and where is the converter.
I have a 30 foot 10gauge extension for my 200 watt remote panel. The controller is by my battery. I don't see much loss with that. I tried putting a controller on the panel with the same cord and lost about 10% of the power.
Make sure you get pure copper not CCA. Copper Coated Aluminum. With that you need 3X the size to flow the same current.

 

[Randy]

Excellent, thank you for the tips! Just to clarify, with controller at battery lose was less than 10%?

 

[smritte]

When I tested this, I used a standard 120 watt panel. Mid day, angled at the sun, 12 volt panel would be rated at 10 amp's. I got almost 8.5 amp with the controller at the battery and a low 7 amp with the controller at the panel.
This was my solar set up for several years with my little trailer.

When I built my next trailer, I used a bigger panel with a 100 volt controller. The trailer is set up so I can tie in external panels. Using the same extension, with the second panel in parallel, (controller at battery) the loss was about the same. Running in series kicked my voltage up to about 35 volts and the loss dropped considerably.

12 volt panels run between 16-18 volts, unregulated. The higher the voltage the less loss you have in wiring and connectors.

 

[Offroad Bound]

100 volt controller? That really left some expansion on the table for you. To achieve the 35 volts, what size panels were you using?

 

[smritte]

12 volt panels. The current rating didn't seem to matter. I've measured open circuit voltage as high as 16 volts on a 12 volt panel. Also, I have seen 32 volts on my buddies 24 volt panels.
The controllers normally have either a 48 (ish) volt max or the next step which is 100 volt. Most of the common higher end controllers are 100 volt.
If I got the 48 volt, I should be good with two panels but not with three in series. The 100 volt wasn't that much diffrent in price and it gave me wiggle room to play around. OH and it had Bluetooth....

Where this would be necessary for me would be if I needed to chain my Trailer, Cruiser and backup folding panel. The amount of wire to do this would mean quite a bit of loss, especially in parallel. To eliminate this, I would series them. Now I need bigger than a 48 volt controller.
Did I actually need this set up, probably not. Will I ever need this set up, again probably not.

The reality of it is, I just love to play around with things and see what happens. I'm not happy unless I push parameters and see if it fails.