What ga wire do I need ?

[dockmasterdave]

I currently have a WFCO 45 amp converter. I have never been happy with it.
I have a voltmeter that tells me it is almost always at 13.6 volts. It never drops below that and in 8 years I have only seen it hit 14.4 once. I e mailed Randy at best converter a while back, and he suggested replacing it with a PD 55 amp wildkat. I bought that one and it came yesterday.
The instructions say " DO NOT " replace a converter with a higher amperage one.
I was hoping that the factory might have used a heavier wire than necessary, just to simplify their stock by using the same wire they have for a larger unit.
I checked my wires and they clearly say 6 AWG.
Does anyone know if #6 AWG is sufficient to handle 55 amps to a 2 battery bank at 20' ?
Thanks for any input. If I needed to run heavier wire, I can get at everything to do that. I just figured there must be a formula for amperage at a certain distance and wire gauge, and if any would know, it would be someone on here.

[2112]

I have to ask, what is the total Ah of the batteries you wanting to charge? Do most typical battery banks demand more than 30A charge when depleted? And if it does, how long will the current be above 30A? Mods may not be needed.

[time2roll]

Get the exact length and terminal eye hole size for probably just a few $$$ more:

https://www.genuinedealz.com/products/custom-battery-cable-marine-grade-by-the-foot

[CA_Traveler]

I love it when a plan comes together!

[dockmasterdave]

Update
I looked online and found a 60 amp surface mount circuit breaker for $33. I can get 2 36" 6GA battery cables with eye ends.
1 will go from the battery terminal to the circuit breaker.
The other will go out of my battery box to connect to the existing 6GA wire. The existing 30 amp fuse block can stay in place to run my other loads.
They currently have the 10GA to 6 GA connection under the TT with a huge wire nut. I will put an eye on the existing cable and connect to the new cable with a bolt, then waterproof the whole connection.
This sounds like the RIGHT and safe thing to do. Much better than the factory setup. Thank you for pointing me in the right direction.

[CA_Traveler]

Food for thought: What works for 120VAC doesn't translate directly into 12V.

That 0.78V drop for 120VAC results in 119.22V and so who cares? But at 14.02V on a battery system something to consider... or not. :h

[CA_Traveler]

My calculator shows that 14.8V, 18', 6ga will have a 0.78V drop or 14.02V at the battery. Probably OK.

I would extend the 6A wire from the charger to the battery with a CB and tap off of that for the panel.

Actually I would upgrade to 4ga which would result in 14.3V. But I'm into performance and maybe even bragging rights.

[time2roll]

Really help to post some pictures of what you are looking at.

http://photoposting.is-great.net/?i=1

I get most of my electrical provisions here: https://www.genuinedealz.com/

Yes you need to upgrade the #10 wire. Also verify the grounds are #6 so the entire charging loop has the proper rating.

[dockmasterdave]

I just measured the run, it is 18'
If I want to extend the 6 GA with another piece of 6 Ga, I will probably need to replace my fuse block.
It is a simple 2 sided fuse block with 2 30 amp fuses and is wired completely with 10 Ga.
I am guessing that since one side/wire is connected to the 6 Ga run to the power center, that runs all my 12 volt in the TT.
Since the other side/wire bypasses the 6 GA run and heads back the trailer it is probably for my non fuse panel related items, IE break away braking and co/propane detector ?
I looked online but didn't see anything like the fuse "block" near my batteries. Any suggestions on where to get one ?

[KD4UPL]

Generally #6 is good for 60 amps and #10 is good for 30 amps. It really all depends on what heat rating the insulation is good for and also what heat rating the terminals are rated for. Most devices probably have terminals rated for 75 degree C. Wire size is also dictated by length and thus voltage drop.
In your situation it seems like they used the #6 to reduce voltage drop due to the long run of wire. This is a normal thing to do. Just because a certain size wire will handle a certain current without overheating doesn't mean it won't lose some voltage getting to the other end.
I would extend the #6 with more #6 directly to the battery terminals, fuse it at 60 amps, and hook up your new converter. I suspect voltage drop won't be an issue but you didn't say how long the run is.

[dockmasterdave]

It just got WEIRD.
I went to take the cables off the battery to switch the converters and found the 6 GA runs the whole length of the run and in the last 3 feet, they wirenutted the 6 GA to a 3' piece of 10 GA.
My fuse block, at the battery has two 30 amp fuses and is wired in all 10 GA.
Is this 3' length of 10 GA going to mess me up ? What does that do to my reading of the ampacity chart ?
Do I calculate using the smallest GA wire in the run or doesn't that short of a 10 GA run matter ?

[time2roll]

#6 is fine with 55 amps. If you pull wire I believe #4 is the max that will fit the connectors. You may also want to check if you have a fuse or breaker near the battery to verify rating. The PD will charge like a rocket when needed and consistently drop to storage voltage when expected. Make sure the jumper is in the lead-acid position, not lithium. Ampacity with 105C insulation is 100 amps for #6 but it is usually the voltage drop that becomes the size issue. Either way you are fine for now.

[dockmasterdave]

I have no idea what all the abbreviations mean on most of the ampacity charts, such as THHN THWN etc. However I did find an oversimplified one (below ) and based on this chart and others I am guessing between 65 and 75 is the amp rating. I would still like to hear from someone who knows more than I do and understands all the abbreviations etc.

[img][/img]

[Lwiddis]

Rare will a battery bank accept 55 amps for long.

[Lwiddis]

WindyNation wire size chart...