Rewiring battery bank to charger/inverter, couple of ?'s

You are good controller-battery for sure. The array end with #4 should be ok, but let others advise on details where you have a combiner and series or parallel and all that.

Perhaps a new thread for that specific question, naming your controller model, specs, panels, array configuration (with options?)

By 'close to the battery bank', I mean that the controller will be inside the trailer so I can see the readout, there is a cabinet at the front that is about 4 feet run from the toolbox where I'll have the batteries.
I'll also be running 4AWG from the controller to the arraqy, will that be good enough to handle the load? I've got a total of 300w of panel, putting out max 18A in full sun.

Yes, you will not have a problem with voltage drop controller-battery with the controller right by the battery. But by now having such a long run from controller to array, that might be a problem without fat enough wires. Especially with MPPT, where you want all that voltage.

Another "issue" is that by the battery, the controller is out of sight, so if it has read-outs, you can't see them. Now you need to spend extra on a remote read-out or use the Trimetric if you have that anyway, in which case not a problem.

Some have the controller inside so they can see the read-outs which means it is maybe half way between battery and array with voltage drop on both ends. Doing it yourself means you can get it to the best compromise for your needs.

If the solar controller is close to the battery bank on short, large, dedicated wiring, then life is good.

Jim

I plan to install the solar controller a couple of feet from the battery bank, with a long run back to the array. The controller won't be directly connected in any way to the converter other than both being wired to the batteries. I can't see how that would cause any issue?

My issue, which might be what you are looking at, was that I needed to use the existing DC panel lugs (near the converter)-battery wiring for the controller to battery too.

If I used that wiring as part of the long controller to array wiring, I got the problem that the converter would then charge 'through' the controller which caused problems (don't do that!)

The compromise was to have the controller near the converter and accept longer controller-battery wiring than ideal. My wiring there is fat enough not to have too much voltage drop and it has worked out ok. Your controller instruction manual might give you an idea of the pros and cons of which way to go.

Guys here are pretty good on that topic in general and may have the same controller, so over to them-----

BFL13 wrote:
The controller location and wiring might do with another look, not sure.

The controller needs to "see" the battery voltage as is with as little voltage drop as possible so the controller will control at the set-points it uses. eg, if voltage drop from controller to battery is 0.5v at the current, and set point is 14.5v, then the controller will "see" 14.5v when batt is only 14.0v

So with that, the battery will be undercharged perhaps or at least you won't get to as high a SOC in the daylight available. Or you could make the set-point 15 :)

So usually they say put the controller close to the batteries to avoid that and it is ok to have a longer wire run from controller to array.

It is ok to have the controller-battery wires sharing with the converter where the two "chargers" are in parallel at the DC panel battery lugs. It is not ok to have the array wiring meet with the converter's wires before going to the controller, where the converter will "charge through" the controller.

(I got some good help from the forum here with that issue last winter when re-designing my set-up)

So the nice new programmable controller will be fussy about seeing the real battery voltage for its programs. MPPT also needs good voltage from the array to work right.

The controller instruction manual will likely have something to say about all that. Anyway, I don't know how it all is in that rig, now or as planned, but could be worth a review of the plan to make sure the solar side will be ok too.

I can certainly install the solar controller immediately adjacent to and directly connected to the battery bank - there would be a longer run from the array to the controller, but it maxes out right now at 18A, so 4AWG would be more than ample for a 30' run.

beemerphile1 wrote:
I'm a little confused. You said "if I do put in an inverter" but in the original post you said you have a charger/inverter. Do you currently have an inverter or a converter? You need larger wire if you have an inverter/charger.

Sorry for the confusion - I meant to refer to the converter/charger, not an inverter!

OnaQuest wrote:

renoman69 wrote:
Run the wire every time. Frame grounds are way too unreliable.

Since when? Every automobile on the road has multiple circuits wired this way.

Does your starter have a ground cable all the way back to the battery?

Look @ a manual for any car and why are there so many grds? If they were good only 1 would be needed but my Superduty has 6 grounds from body to frame.

HiTech wrote:
It is slightly better to run a dedicated ground than a well done frame ground. If they salt the roads there, a ground to frame may corrode more easily over time.

Jim

a poor frame ground is bad news, but then so is a bad wire ground.

However, using good techniques and connections a good frame ground is much better than dedicated wires. In fact, I did a recent test of frame ground resistance vs and equal length of #3/0 welding cable. My frame ground had 1/3 the resistance of the #3/0 welding cable. With 100A going to the batteries when charging (4x T-125's) the current through the welding cable was a shade over 30A, so there was 70A going through the frame ground path.

Results will vary amongst trailers based on frame construction. If your frame is welded not bolted and reasonable size use the frame. if it is bolted construction then individual wires may be better. Frame has much larger cross sectional area and multiple paths even though the resistance/cross sectional area for the frame is about 5X that of equivalent copper cross sectional area.

for my frame grounds I drill and tap a hole then get a square washer the same thread size, grind down through the paint/powder coat. tighten the nut down with a bolt and then weld the nut to the frame. Then use copper paste on the threads and lock washer of the bolt. for heavy wire I use a 5/8" square nut, smaller sizes for smaller gauge. heavy wires crimped with a tin plated lug and attached using a hydraulic hex crimper tool, then sealed with adhesive lined heat shrink.

If you aren't drawing high currents, it probably doesn't matter much either way.