I'm working on a couple of solar panel projects here is the list of question I have.

1) I"m looking for a wire chart that shows how far you can run a specific gauge wire at 12vdc before there is significant voltage loss.

2) I have 18/4 cable, what gauge is the wire if i twist two of the conductors together?

3) I have a 35w solar panel how long does it take to generate one amp hour of power?

4) Lets say i have a 1 amp draw on a 65ah deep cycle battery and the draw is continuous for 10 hours (dusk till dawn) how may amps have i used?

5) Most boats have 2 battery banks. One house battery (for electric appliances) and one reserved battery to start the boat motor. I want to solar charge both batteries then disconnect the reserve battery so there is no load on it while i use the house battery. The solar charge monitor i have only has one battery terminal. I tried to wire the coil of a relay across the solar input terminal so that when there was sunlight the relay would close the circuit on the reserve battery so it could be charged but the coil took to much power there was not charge output the solar panel is only 10w. Where can i find a low current relay or what is a better method?

6) I'm setting up solar powered motion detector led lights but i can't put them in the sunlight and have them where that need to be....I want to set up a remote solar powered battery charging station then run wire to the motion detector led lights. another problem is that they are lower than 12vdc. Its simple enough to by pass the solar panel input then connect my own power supply. What is the most efficient way to drop the voltage to 6vdc step down transformer or resistor? is there an adjustable step down transformer?

7) I bought automotive 12vdc led lights they work great i could also set them up as motion detector led lights where can i get a 12vdc outdoor motion detector and a day/night photo electric switch?

8) last problem the solar panel i bought didn't come with mouthing brackets. I want to mount it on 2x4 then sit it on the ground but i need to adjust it to the correct angle toward the sun. Where can i get or make an adjustable bracket?

  • 1
    \$\begingroup\$ Most of your questions have answers on the site already, I may find some soon if you have not searched in the interim. \$\endgroup\$
    – Solar Mike
    Commented Aug 12, 2017 at 6:32
  • \$\begingroup\$ West Marine has charts for this on their website under Marine wire size and ampacity. \$\endgroup\$ Commented Jun 8, 2020 at 18:51
  • \$\begingroup\$ "Lets say i have a 1 amp draw on a 65ah deep cycle battery and the draw is continuous for 10 hours (dusk till dawn) how may amps have i used?" 1 A, as stated in the beginning of your question. \$\endgroup\$
    – winny
    Commented Oct 8, 2020 at 10:42

1 Answer 1


1) see here : Simple voltage drop question

2) if two cables in parallel, the current capacity is double, if still the one cable then the original current capacity.

3)assuming 35W output at 12v the current is just under 3 amps, AH is amps * time so 20 minutes assuming no other losses.

4) see ans for qu 3, 1A * 10 hours = 10AH.

5) use two solar controllers is one option or a controller with two outputs.

6) source the voltage converters (bay of fleas etc) resistors will waste power.

7) most Do-It-youself places have those - make sure of the input voltages...

8) Two bits of 2x4 to form a triangle - adjust the length of the sides to get the panel angle - you can purchase brackets, how much you spend is your choice, if you make them they will need to be strong enough to support all the loads : wind etc


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.