DC Charging

Run with what you have for now. If the plan is to charge faster, you need to either parallel with another wire (larger if possible), or possible use the existing wire to pull a new one.
I would start by putting a digital volt meter from the positive of the charger output to the battery positive, measure the voltage. Repeat on the ground / negative side. add the two together, and that is your voltage drop - the higher the amperage the higher the drop - test when you are running max amps (bulk charging) to get a worst case.

BFL13 wrote:

Easy for us, just stick the "deck mount" converter up where the batteries are and leave the original wiring alone. No fuss, no muss.

Yeah, do this then run #4. :B

If you want to dramatically see the affect of wire size on voltage drop between you converter/charger and your battery(ies) during recharge, use a four-place digital voltmeter to measure the voltage at your converter's/charger's terminals while it's charging your battery(ies), and then use the same voltmeter to measure voltage on your battery's(ies's) terminals.

The voltages won't be the same ... but ideally they should be the same for fastest charging for any type of charger/converter you might be using. The larger the wire size the less difference there will be in the voltage at the two locations while the battery(ies) is(are) being charged. Increasing the wire size will seem almost "magical" in how it speeds up the charging process.

Ok I seem to have the same issue with the door so I'm thinking of running #4 wire in flexible plastic conduit outside under the floor or use the existing #6 to the panel and move the converter mounted upside down to the ceiling in basement forward storage compartment and run #4 from there about 5 ft. through the floor to the fuse/battery.

I know someone will tell me my electrons will be upside down if I do that- but isn't that what the inverter is for.:-) Proton electron and neutron are at the bar drinking. Bartender says to the neutron "for you no charge."

it is correct to say, "Increase the wire to #4, but how to do it? Where is the route? Eg, we have the trailer door in the middle and the converter/ power centre is on one side of the door and the front where the batteries are is on the other side of the door. No cabinets where the door is to hide any wires.

Can't be done! Only way is to get the converter and batteries on the same side of the door. You can't use the wall cavities either--total zoo.

Easy for us, just stick the "deck mount" converter up where the batteries are and leave the original wiring alone. No fuss, no muss.

MrWizard wrote:
I would increase the wire size to #4

the trouble with amperage ratings, is it is the safe rating for "HEAT", WIRE TEMPERATURE, how much current the wire can carry before becoming dangerous

not the rating for voltage drop,
you will have less voltage drop and more efficient charging using a larger gauge wire

voltage drop is very important in 12v~14v systems

X2

The pos wire out by the battery will have a fuse or a DC circuit breaker there that might be too small in amps now.

You have an opportunity here to mount the new converter up front close to the battery bank, which will improve the DC charging by having shorter wires to the battery (needs a fuse on pos wire to battery near the battery) But you need a 120v receptacle up there to plug the converter into. (which you can add if needed)

Some people do that by putting it under the bed or sofa , whatever you have there on the inside of the front cap. Usually, they drill a hole in the floor for the wires to go down and then up to the tongue instead of going through the front cap.

While you are at it, you could add an inverter in the same place by the converter. The inverter fat DC wires can go over to the converter (or VV) and then just the one set of fat wires can go out to the battery bank. You then have to arrange one of several ways to get the 120v from the inverter to the items you want to be live when the inverter is on.

The existing battery to DC fuse panel wires would stay the same to carry RV loads from either the battery as now, or also now from the new converter. Those loads are all low amp stuff, not high amps stuff like charging, so those wires are fine for that as you know since they work now. :)

Saves lots of work removing the old converter and maybe having to re-wire--not easy to "pull wire" in an RV!

The original converter an Atwood Fortron integrated into the panel is not working and was bit anemic in charging the battery when on shore power when everything was running- I opted for a 4 stage Power Max -My thoughts were that I could eventually add a battery - add additional DC circuits for equipment and better battery management with a 4 stage converter. The old converter I had is no longer made so swapping it for a more modern converter for nearly the same cost made perfect sense to me. I was thinking I could do the swap now to get me running again and add a battery and upgrade the wire later. I know AC power pretty well but not sure of DC and charging systems. Does the charger push or the battery pull Amperage I guess is the simple question? As most circuits draw what they need and are fused/or have a breaker. I would think a second battery would require larger wires to charge efficiently but could I get by now as is?

I would increase the wire size to #4

the trouble with amperage ratings, is it is the safe rating for "HEAT", WIRE TEMPERATURE, how much current the wire can carry before becoming dangerous

not the rating for voltage drop,
you will have less voltage drop and more efficient charging using a larger gauge wire

voltage drop is very important in 12v~14v systems

You can leave the wiring as is, since #8 AWG is good for a 55amper.

But what is the reason to go to 60? What model is the old converter and what would be the model of the 60?

Adding a second battery will not make any difference except it will take twice as long to recharge the bank---but also you get more time to discharge, which is good. In fact you get more than twice the discharge time at the same loads, due to the magic of Peukert Effect.