Batt To Inverter Cable Length Question

[hellosailor]

"buy 20 ft. of welding cable."
NO!
Welding cable uses very thin flexible strands, much thinner than boat cable. It normally is not tinned, either. As a result, it can oxidize and punk out much faster than real boat cable, requiring replacement much sooner as well.
Your best bet is to check the wiring runs, tape up some 5/8" line to dummy them up. Measure twice (!) and then order the cables from genuinedealz.com, who usually have the best price for a cable and will put the proper lugs (check battery bolt sizes too) on for a very reasonable fee as well. Good crimps make a big difference!


But having answered that...there are many good online "voltage drop" calculators.
Voltage Drop Calculator - for single and 3 phase ac systems and dc systems


You key in the cable length, size, material, amp load (for a 2000W inverter that could mean 2000/12=166 amps!) and it will tell you the voltage drop you would get.


When you consider that a "12" volt system is 12.7 volts on a great day, and that a 12.0 v supply would be nearly dead...you want to size those expensive cables so that you will have a minimal voltage drop. Your inverter may not like seeing anything less than 12 volts, check the specs.


But please, do run the calculator (any calculator) and play with cables lengths and gauges to see for yourself how big a difference this can make.


And don't cheap out on the cables, you can quickly live to regret it. If you really need to pinch pennies, you can find fully tinned "machine cable" which is almost the same stranding as boat cable. But welding cable? Nah, I'd buy copper [plumbing pipe before I did that. And then paint it inside and out.(G)

[rwidman]

Originally Posted by Cadence

Grats! You are the first person to indicate mounting an expensive inverter directly above the batteries may not be a great idea from the standpoint of fumes. They may be sealed batteries? If not kiss the inverter off more quickly than normal.

See post #21

[hellosailor]

Years ago Fiat had a sport model (124? 128?) that had the battery located in the trunk for weight balance. And they earned a reputation for having the trunk eaten out by battery fumes.

Miata did their sport with a battery in the trunk--and chose an AGM to avoid the fume debacle.

BMW, Audi, others currently make SUVs and CUVs with the battery relocated "under the spare" in the rear compartment, and they ALL use either a vent tube, running from an enclosed (sealed) battery to the outside of the car, or an AGM battery.

This is all to say there is extensive reason to believe a battery compartment should be SEALED and VENTED with nothing except the battery in it. Just, you know, in case there's any solid engineering reason to believe wet lead batteries emit caustic and corrosive fumes.

[transmitterdan]

Welding cable is fine if it's the right size. 4/0 is the right size. Seal the crimp lugs with adhesive shrink wrap (twice if you can). You don't need tinned wire.

[rwidman]

Originally Posted by transmitterdan

Welding cable is fine if it's the right size. 4/0 is the right size. Seal the crimp lugs with adhesive shrink wrap (twice if you can). You don't need tinned wire.

If welding cable were fine they wouldn't make boat cable. There's a difference. I'm not saying welding cable won't carry the current, you could use building cable from the home center and that would work for a while as well.

If you want to do it right, use boat cable. If you take pride in your boat and in your work, use boat cable.

[transmitterdan]

Practical Sailor and others have done tests to prove what common sense tells us has to be true. A proper gas tight crimp will last just as long with copper wire as with tin plated copper wire. Seal the crimp with water tight adhesive and it will outlast the boat.

Now if want to be "doing it right" use silver plated wire.

[btrayfors]

Guys,

It's hardly worth arguing over, in this case at least.

The OP needs about 20 feet of heavy cable. Assuming he's going to use 2/0 size cable, the difference between the cost of welding cable and proper tinned marine cable is $54.40 (see table below....current prices).

And, if he finds a place for the inverter closer to the batteries the difference will be a lot less than $50.

I'd say it's best to forego a dinner out and buy the proper (marine) cable.

Bill

[colemj]

Originally Posted by btrayfors

Guys,

It's hardly worth arguing over, in this case at least.

The OP needs about 20 feet of heavy cable. Assuming he's going to use 2/0 size cable, the difference between the cost of welding cable and proper tinned marine cable is $54.40 (see table below....current prices).

And, if he finds a place for the inverter closer to the batteries the difference will be a lot less than $50.

I'd say it's best to forego a dinner out and buy the proper (marine) cable.

Bill

I'm betting the OP will come back and show you that the price difference between local welding cable and shipping in marine cable where he lives would allow him to fly to Morocco for a dinner out.

We have welding cable connecting our inverter. Strangely, it is the only welding cable used on the boat - even though there are large amounts of 4/0 and 2/0 marine cable used elsewhere. This cable is crimped well and sealed with heavy glued heatshrink. No problems.

The thin strand argument doesn't make sense unless one's boat flexes like a plastic toy all over and one uses long unsupported runs where the boat flexing causes 90* bends to occur frequently. In this case, one should be arguing against the boat and not the wire.

The tinned argument is also strange seeing how marine wire outside the US is rarely tinned. Whole boats are made with untinned wire. Large expensive boats. It is only in the US where people start hyperventilating about untinned wire.

The heat rating, etc arguments make sense, and one should choose appropriately rated wire - welding or not.

Mark

[rwidman]

Stranded building wire from the home center would be even cheaper and work. Or, use copper plumbing pipe covered with harden hose for insulation.

The problem with asking for advice on the Internet is that you get lots of advice but much of it is bad advice. Follow it and you may eventually find your boat featured in a "stupid things the PO did" post.

[colemj]

Originally Posted by rwidman

Stranded building wire from the home center would be even cheaper and work. Or, use copper plumbing pipe covered with harden hose for insulation.

The problem with asking for advice on the Internet is that you get lots of advice but much of it is bad advice. Follow it and you may eventually find your boat featured in a "stupid things the PO did" post.

Perhaps instead of just setting yourself up as an expert that is never to be questioned, maybe you could expound on why appropriately spec'd welding cable is inappropriate for this application?

Mark

[exMaggieDrum]

Originally Posted by colemj

I'm betting the OP will come back and show you that the price difference between local welding cable and shipping in marine cable where he lives would allow him to fly to Morocco for a dinner out.

We have welding cable connecting our inverter. Strangely, it is the only welding cable used on the boat - even though there are large amounts of 4/0 and 2/0 marine cable used elsewhere. This cable is crimped well and sealed with heavy glued heatshrink. No problems.

The thin strand argument doesn't make sense unless one's boat flexes like a plastic toy all over and one uses long unsupported runs where the boat flexing causes 90* bends to occur frequently. In this case, one should be arguing against the boat and not the wire.

The tinned argument is also strange seeing how marine wire outside the US is rarely tinned. Whole boats are made with untinned wire. Large expensive boats. It is only in the US where people start hyperventilating about untinned wire.

The heat rating, etc arguments make sense, and one should choose appropriately rated wire - welding or not.

Mark

Some good healthy pros and cons for tinned vs. non-tinned, and welding cable vs. boat cable. Non-tinned wire will work fine so long as it is protected from all the nasty air and water on boats. The trick is to make that happen. Even the most skilled boat electrician can produce a heat shrink "air-tight" cover at the end of a cable where it mates with the lug and still have it leak.

Lugs are not perfectly round. People don't always use the best heavy-duty heat shrink (it should ALWAYS be the kind with adhesive inside and the adhesive should ooze out of both ends when you heat it up for your crimp). Heat shrink (especially the thin stuff) can split on sharp lug edges made by some crimpers (by a lot of different kinds of crimpers). Don't ever put a bend at the heat shrink. If it doesn't pull off right away it will creep off later and not seal right.

The cable should be secured so that it cannot move from its position relative to the post. Otherwise it will work itself and cause a "leak" leading to corrosion. All tinned wire does is to help prevent corrosion when it leaks. Securing the cable helps prevent it from loosening at the post too.

I do use tinned wire and high quality (heavy duty/adhesive) heat shrink and always secure the cable so it won't move. But if you use welding cable you can do this and it may work out fine for you. However, I have worked on some European boats where the untinned wire had corroded so bad that the cables were in fact only half there - in the middle of the cables. Just because it is an expensive boat made in Europe does NOT mean it uses the best quality materials or use best practices in installation. Those of you who have not seen this won't have the same concern I have. Some of you won't see the pounding that some boats take in big seas either.

Regarding the rating of cables - they are important. Heat - oil resistance - insulation quality. Some welding cables may be used in 150 degree environments like you can have next to engines but 99% do not. They are designed to be used in everyday work environments and usually have short cycle times so heat doesn't build up as much (knowing that this is not true in many cases). I am not a welder so am not expert on what kinds of welding cable is available but I bet most of you aren't either. I challenge you to go properly "spec" welding cable for the harsh environments in boat engine spaces. I am sure you can do it, but do it.

Regarding wire size within cables: I wish that all boat cable was as flexible as welding cable but it isn't for two reasons. It has much smaller diameter internal wires. These can corrode much faster if air/water does get in there. So to the extent you can keep that from happening all good. The electrons just want a given amount of metal to travel and the air space between the wires is not that big a deal.

The other thing is the insulation though. Run of the mill welding cable insulation is not a rugged as boat cable. This makes it bendier but also makes it less durable. Welders consider it a tool that they replace when it gets bad, like you and I do with a hack saw blade. They need it to bend because they move in an out of tight places and are always coiling and uncoiling it. You don't have to do that with boat cable. You install it once and it stays.

If you wanted to consider your boat cables as maintenance items that you inspect and replace every 5 years go ahead. Most of you will not do that.

Regarding made to order cables: I bet that anyone that does that will either have a cable that if they are lucky will be 5 inches too short or one that is 2 feet too long. I have been running 2/0 cable for a long time and I have never been able to measure the length with a tape measure. Even short lengths I do one terminal lug and try it to see how it will fit. I also make sure the terminals on shorter lengths match up to the configuration/orientation of the terminal on the other end. Sometimes you need a lug that is 180 degrees (or some other odd orientation) different from the other lug to be able to put batteries in series in close spaces. If you have to force a cable, even flexible welding cable, you will put torsion forces on both ends will cause the heat shrink to fail and get corroded. Not to mention causing the crimp to fail.

Which brings to mind that batteries are the very most corrosive places on a boat and where the corrosion protection has to be 100%. If you do the welding cable "right" no problem. Wrong and you check the battery fluids one time and the battery cable falls off of one of the lugs because the wire had dissolved.

Not trying to be argumentative but there are some who seem to think there is a conspiracy of boat cable fanatics trying to get everyone to buy expensive cable. An exaggeration for sure but sometimes it sounds like it. I absolutely hate to buy the spendy stuff myself. I spend hours researching products I want to add to my boat to get the lowest cost for what I am trying to do. I don't have a lot of money. Whatever I spend on one thing is a trade-off on some other stuff I really need or want. But I won't compromise on wire or the installation of it.

I don't think I will convert any of you diehards but it is a shame that some amateurs will actually listen to some of this cheap advice. I almost fell out of my chair when the OP said that he got out of this thread that he should go out and buy welding cable since he decided that was the consensus. It is not the consensus.

I am NOT saying that you absolutely should not use welding cable, but if you do, please do as much as you can to install it the best way possible. Buy the expensive heat shrink. It is VERY expensive. Don't cut it too short to save a buck or not go back to the boat store because you didn't get enough the first time. Shrink it right. Secure the cables. Don't run them laying on anything - secure them with wire times and cable clamps out of the bilge and not under the engine. Don't bend them tightly at the terminal. Don't pinch them with anything - the insulation won't take it. Get heavy duty cable of the right size and spec. And inspect it often - look at and touch it the entire length of the cable, especially at the terminals. And then go boating.

[DeepFrz]

I don't see any problem if one uses the proper color coding, red and black or red and yellow or plainly marks the cables with Red and Yellow heat shrinking and uses proper sealing techniques. This cable seems to meet the specs required.
http://www.google.ca/url?sa=t&rct=j&...84349003,d.aWw

[transmitterdan]

If you don't want to believe me read the Practical Sailor test results. All wire corrodes in salt water/fog environments. It's a fallacy that bare tinned wire will survive a long time without being protected. Tin plating that is corroded doesn't look as bad (isn't green) as corroded copper thus the myth that it corrodes less. That and a lot of people make extra profit from the myth.

Locomotive cable is also a good choice.

[exMaggieDrum]

Originally Posted by DeepFrz

I don't see any problem if one uses the proper color coding, red and black or red and yellow or plainly marks the cables with Red and Yellow heat shrinking and uses proper sealing techniques. This cable seems to meet the specs required.
http://www.google.ca/url?sa=t&rct=j&...84349003,d.aWw

This looks like good cable. Just needs to be installed right. Whatever cable color you use should be color coded and labeled at each end to match the application. To do otherwise is asking for trouble.

[barnakiel]

Fuse it.

b.