I don't necessarily want or need to hear it's fine as is, I'm just saying that I've been told by xantrex which cable to use and how long of a run was ok, so I did that. If that's not right, I can replace the cable I guess, but I cannot imagine that there is a significant difference in voltage drop from thick-strand cable and fine-strand over only about 13 feet.
There are charts that demonstrate voltage drop over a known distance, and in the xantrex manual it says that the voltage drop per foot for 1/0 cable is .020 per foot, and in another place on xantrex' website, it says that anything under .25 total drop is good. at 13ft, including the connections, I'd say I'm just over the .25total drop. I need to just pull the inverter out and hook it up right at the battery and find out if it'll work that way, to be sure.
If you use welding cable, it will be like working with rope. Easy to work with but expensive. Besides voltage drop from the cable itself, a hard draw like the microwave, etc. will cause a big voltage drop from the battery even if you are close. When I had my 2 6 volts, I could use my coffee maker down to about 12.2 volts before I would get the low voltage alarm. It's been a while so I don't remember exactly. A while back Piano Tuna mentioned either high draw or voltage drop. I think he was right on. Unfortunately I think you will have to replace your wires which I'm sure will be a pain. Any chance you can mount the inverter closer to the battery and then extend the AC side to the transfer switch? Even if you do that, I would upsize the wires and go with a fine stranded type.
My Dometic microwave draws 1591 watts. It is the item that gives my 2500 watt inverter the most trouble.
To measure voltage drop.
Set up volt meter at the battery bank. Turn on coffee pot. Take a reading at the battery bank.
Then repeat the above measuring at the DC inverter terminals.
I do not know what the inrush on a microwave is--but on occasion I have to add a small 100 load to my inverter *before* I turn on the microwave. It has not happened for a while.
There was a case of a gentleman here with four six volt batteries who had great problems trying to run high draw items. The six volt batteries just don't appreciate heavy loads, so the voltage drops internally.
It may be that the battery bank will need to be doubled in size (four six volts) or that 12 volt jars wired in a balanced manner may be needed.
Kustom Koach Class C 28'5", 256 watts Unisolar, 875 amp hours in two battery banks 12 volt batteries, 2500 MSW watt inverter.
Not to beat this thread to death any longer, but I thought I'd give another update.
I checked and the jumper wire, the one that was loose, is also smaller than the other wires I'm using, so temporarily I made up a larger jumper between the 2 batteries and it helped a _little_ more. Still not everything I wanted, but good enough for me, I think. (although I have an LED flickering issue I'm going to post about in a minute).