6 volt battery wire size

[gsncs1020@aol.com]

I have 2000 Bounder 39z. We have been full-timing for 18 years, but now I "must" use a CPAP machine to sleep with some changes where necessary so I could boondock if I wanted to. I have six 6-volt deep-cycle interstate batteries. This time 4 are in the battery compartment and I added two on the other side of the coach. They run through a Xantrex RV2012 GS inverter and I have 3 125 watt solar pannels on the roof flat. I have a controller that will start the generator when batteries get to 11.5 volts, or wherever I want to set it and charge the batteries to absorb charge. This way I don't have to worry about the CPAP losing power during he night.

Now the question. The four batteries that came with the coach have I would guess "0" size wire, when I added the extra two batteries on the other side of the coach I used #2 wire to connect them together and to the primary positive post for all battery's. Does anybody see a problem using the #2 wire ? and if it is going to be a problem, how about if I run a second # 2 wire. I would think that two #2's would be the same as a "0" wire.

No matter how big the wire is, the connector on the ends are about the same size and should carry the same voltage.

[NWJeeper]

The question for you is how much amperage can your inverter draw from the batteries? My 1000w Prosine manual said to try and keep the inverter within 5 feet of the batteries and to use #2 wire. I too have 6 6V batteries. 4 are about mid rig and two are up front behind the grill. For those I used 3/0 as it is a long run back to the other 4 and mostly because I got the wire for free. With DC wiring I tend to error on the big side rather than the small side as the consequences can be disastrous. I always use welding cable as it is much easier to run and work with rather than battery cable. Your inverter manual should spell out what wire size to use depending on how far away it is from the bank. For the extra 2 batteries I would use heavier wire since they are away from the bank a bit and never smaller than what is used between the batteries.

[hermanmullins]

Here is a web site that has the information on cable size, amp load and length. As has been stated before welding cable is your best bet.

www.directwire.biz . Click on downloads, then click on item one brochures and go to page two. There you will find a chart with the info. you need.

Happy camping and keep on breathing at night wit out worry.

[Guest Wayne77590]

Glencheri,

By using another #2 wire, you would have what is know as a parallel circuit, and in a parallel circuit, the voltage across each of the components is the same, and the total current is the sum of the currents through each component.

So you would have 12 volts going through each of the wires, but your current would be equal to the sum of the current through each branch(wire). The smaller wire would have a slightly higher current than the larger wire, but it should handle anything that you have running.

There is a 0.0673 of an inch difference in the diameter of a #2 and #0 wire. Until you get over 110 amps, there should be no negative results. For the best determination, contact the manufacturer, a battery compy, or an electrical engineer.

Good luck.

My CPAP has the ability to run off of regular dry cell batteries (C-Cells or D-Cells) although I never have used it that way. It also has a humidifier, which I don't need here on the Gulf Coast.

Have you checked your manual to see how much current is being drawn by the CPAP when it is running? Do you leave it plugged in all day? (I don't.) I just don't feel that the little pump delivering air can draw that much current. You do have to remember that the current draw on 12v will be different than 115v. An amp-meter or the manufacturer should be able to provide you with answers.

Just curious, what type CPAP do you have? Is it 115v and 12v, or just 115v with a little square box providing the 12v, or just 12v.

Also, some CPAPs cannot be run on an inverter. Check the manual.

Good luck.

[ClayL]

if you go HERE ,

you can download a small program that will let you enter the length of your cables, current draw, and how much voltage drop across the cables you are willing to accept (I usually use about 1 1/2 percent of 12.6 or 12.4 volts). It will then calculate the wire size for you. Or it will tell you what the drop will be for a given cable size.