Teardrops n Tiny Travel Trailers

by **Shadow Catcher** » Tue Jun 22, 2010 7:53 am

One of my concerns was power loss when off grid, ya got only so much battery and ya don't want to waste it. The remote extension cord for the solar panel will be 8 or 6ga.

by **Blackjack** » Tue Jun 22, 2010 9:09 am

eamarquardt wrote:There's more to correctly wiring DC than AC (meaning size is more critical) because the power loss in low voltage DC is greater (proportionally) than in 120 V ac.

The important factors are current and length of run. The best site I've found to help is:

http://www.solar4power.com/solar-power-volt_drop.html

Hope this helps.

Cheers,

Gus

Gus, while I totally agree with you as far as power loss in running DC. The same goes for AC use (to an extent). Unless you plan to run a great distance, the loss in voltage is minimal, and you would not notice a difference. Especially if you are just running just a couple of lights for a short time. Most TD's are what...8 to 10 feet? You would not see any loss if you use 18 gage wire for lighting. If you are speaking of loss of battery power, it isn't the wire size that matters that much, it is the amps that are being used to draw from the battery that is an issue. The higher the amp's, the higher gage wire is needed. These little 12V lights do not draw hardly any amps at all, unless you keep them on all night and all day. Then your battery will of course drain...slowly. But if you are going to use an inverter, then you should use a higher gage wire (battery cable). Now, if you are using anything that uses an heating element, such as a coffee pot or hair dryer (12V). Those types use a higher amperage than little lights, or even a stereo. If it concerns you, by all means use what ever gives you peace of mind. It just isn't necessary.

BUT, if you are running ANY 120V outlets using shore power, do not use anything else but wiring designed for that use (12G).

All my point was, is that you could use 18 gage wire for your lights, fan, and other low amp devices and have nothing to worry about. If your concern is items that use higher amps, then by all means, use a higher gage wire. But, if you look at just about all 12V appliances, you will see that they do not pull that much, and the wire will not heat up at all, if that was also a concern.

Oh, and running a 10 gage from the battery to the circuit panel is a good idea. I wouldn't use anything less than that.

Just my two cents worth. I see it this way: This is your build, have fun, and enjoy these little campers. I am loving mine.

Robert

by **eamarquardt** » Tue Jun 22, 2010 10:54 am

Blackjack wrote:
eamarquardt wrote:There's more to correctly wiring DC than AC (meaning size is more critical) because the power loss in low voltage DC is greater (proportionally) than in 120 V ac.

The important factors are current and length of run. The best site I've found to help is:

http://www.solar4power.com/solar-power-volt_drop.html

Hope this helps.

Cheers,

Gus

Gus, while I totally agree with you as far as power loss in running DC. The same goes for AC use (to an extent). Unless you plan to run a great distance, the loss in voltage is minimal, and you would not notice a difference. Especially if you are just running just a couple of lights for a short time. Most TD's are what...8 to 10 feet? You would not see any loss if you use 18 gage wire for lighting. If you are speaking of loss of battery power, it isn't the wire size that matters that much, it is the amps that are being used to draw from the battery that is an issue. The higher the amp's, the higher gage wire is needed. These little 12V lights do not draw hardly any amps at all, unless you keep them on all night and all day. Then your battery will of course drain...slowly. But if you are going to use an inverter, then you should use a higher gage wire (battery cable). Now, if you are using anything that uses an heating element, such as a coffee pot or hair dryer (12V). Those types use a higher amperage than little lights, or even a stereo. If it concerns you, by all means use what ever gives you peace of mind. It just isn't necessary.

BUT, if you are running ANY 120V outlets using shore power, do not use anything else but wiring designed for that use (12G).

All my point was, is that you could use 18 gage wire for your lights, fan, and other low amp devices and have nothing to worry about. If your concern is items that use higher amps, then by all means, use a higher gage wire. But, if you look at just about all 12V appliances, you will see that they do not pull that much, and the wire will not heat up at all, if that was also a concern.

Oh, and running a 10 gage from the battery to the circuit panel is a good idea. I wouldn't use anything less than that.

Just my two cents worth. I see it this way: This is your build, have fun, and enjoy these little campers. I am loving mine.

Robert

Wasn't arguing, quibbling, or bickering or countering anything anyone else was saying. I just thought the site cited was pretty cool. All these charts, formulas, rules of thumb are guidelines. The problem with "rules of thumb" is that there are always 4 other digits (unless you have accidently cut them off).

The reason gauge is more important in low voltages is that running the same current in the same wire both ac and low voltage dc will lose the same number of volts (E=IR). If you lose 6 volts of your 120 volts your load won't even notice the difference. If you lose 6 volts of your 12 volts your load is gonna notice the difference.

I think it helps to understand what's happening so you can make an "enlightened" decision.

An acid test for any wiring would be to dummy it up, turn on the juice, and measure the voltage across the load as close to the load as possible to see how much of a drop your wiring is causing and the effect on your light, radio, computer, tv, etc. Then you'll know for sure before you wire it up for good.

Cheers,

Gus

by **bbbrt76** » Tue Jun 22, 2010 6:07 pm

Blackjack wrote:After reading most of the post on this site concerning what gage wire should one use, I was amazed that most say (from the fuse panel to devices) 14 gage. I have been in the low voltage wiring business for many years, and I do not understand, because, 18 gage is more than sufficient for even 24 volts, and that is a constant 24 volts, not momentary. If this was a higher voltage, perhaps 14, but it seems to me that purchasing 14 gage wire compared to 18/2 stranded wire is wasting money. But then again, that is my opinion. Heck, if you want to use 6 gage wire, be my guest. What I am really saying is, this is very low current, and the need for a thicker gage wire isn't necessary.

required wire size depends on amperage draw (and distance) not voltage, since 24v systems can do the same amount of work with half the amperage of a 12v system the 24v system can use a smaller conducter (though requires a thicker insulator, but most wires are more than sufficiently insulated for either use)