Typically when there are more than one or two wires on a battery post, one goes to a bus bar instead (or a power post). Although ABYC does allow four terminals on something like a power post lug, crowded battery posts are just not that great. It's hard to get all the lugs to lie flat and make good contact, you get big "pinwheels" of wires going off in all directions, and there can be a lot of leverage on the post. Not that it can't ever work, but ...
I strive to keep battery posts clean, with just the main cable or jumper. Then both the positive and negative go off to a bus bar. Then all the cables attach to the bus bars, and from there go off and do what they do. Easy to label and keep track of what's what. This also provides a place to fuse any wires that are smaller and thus need to be fused differently than the main wire.
Nonetheless, I still have a couple of wires on each battery terminal. That's because the charger temperature compensation cable goes there (has to, since it measures the temperature of the battery bank), as does the voltage sensor for the Smart Gauge.
It is tempting to use the battery terminals if you only have two large cables, or maybe that plus a smaller one. So you just have to analyze your space and decide. Blue Sea (no, I don't have stock) has quite a few sizes and shapes of bus bars and power posts.
Sometimes you can also have something do double duty if you just have two or three wires. For example, a battery switch on the positive side, or the shunt on the negative side if you have a shunt-based battery monitor. You can come onto these with the one cable from the battery bank, then take a couple of wires off to go do their thing.
Uh-oh, wall of text?
So to summarize: Big clots of cables on the battery posts are somewhere between a no-no and just undesirable. Also, unless all of your ongoing cables are the same (large) size as the main cables (which they often aren't), you will want to provide OCP (fusing), and then things would get REALLY crowded.
Maybe this photo of a small system I helped a friend set up in a mini van will illustrate the idea. As you can see, this is physically very small. The box behind the "wings" is what holds the batteries (two Group 27 AGMs) (it is strapped down but that's out of sight), so that gives you some idea of the very compact space. The van has two 100 watt solar panels on the roof, a 300 watt inverter (future 400 watt replacement), some LED lights, and four each of switched cigarette outlets and USB ports. Then there is an "umbilical" cord that runs to a small camping trailer, which has its own small ATO fuse block feeding more LED lights, cigarette outlets, usb ports, and a marine fan. More text below (but not a wall, because, photo!) I know this isn't exactly what you asked about, but I'm thinking it shows an example of the use of bus bars, OCP (over current protection, i.e. fuses or breakers), and how it can be organized in a very small space.
I think it will get larger if you click on it once, and then larger again with another click.
So starting from upper left corner:
1) The wire coming out the "hole" is the positive lead from the house battery bank. There is a Blue Sea MRBF (fuse) right on the positive battery post which you can't see - it has an AIC rating high enough for the short circuit rating of the battery bank, and is sized to protect the main battery cables (using ABYC ampacity table). Just after it "appears" out the hole it goes into the red main Blue Sea battery switch. When this switch is off, no power goes to or from the batteries. (That said, some setups have it so that charging can still go TO the batteries, but no power can go OUT OF the batteries when the switch is off; that's a matter of personal preference and situation.)
Next the main positive wire goes from the switch, to the thing in the center (with the purple bands). That's an item that is a combination of a positive bus and a fuse block made by Blue Sea (called a Safety Hub 100). It organizes and fuses all of the positive wires. I chose it here due to the tight space, and the fact that the 400 watt inverter was going to call for a slightly larger fuse than would go in a normal ATO type fuse block. The purple bands are tubular webbing that covers exposed terminals so they can't accidentally be contacted by other items. Under the central removable clear plastic cover, are spaces for three AMI fuses (larger loads - AMI fuses go from 30-200 amps), and four ATO fuses (smaller loads, fuses up to 20 amps). In this case the ATO fuses cover the lighting (one fuse) and the outlets (two fuses) in the van. There is one empty block left for future.
The larger fuses at the bottom are for the wire that leads to the inverter (10 AWG with 30 amp fuse in this case), the umbilical to the trailer (8 AWG with 30 amp fuse) and the solar controller (6 AWG with 30 amp fuse - 6 AWG could have a much larger fuse, but this way spare fuses don't need to be kept in a bunch of sizes, and there is no need to fuse it higher).
The black switch at the lower left interrupts the positive "umbilical" wire that heads to the trailer. So that can be switched off when it's not connected.
The vertical thing to the right of the Safety Hub is the negative bus. This organizes all the negative wires. Just above it, the cable coming out of the black 'hole" is the main negative wire from the house battery bank. The other wires are the returns from the lighting and cigarette/USB charging circuits, the inverter, the solar controller, and the "umbilical" to the trailer.
The black "box" on the right side wall is the solar controller - it's a Morningstar Sunsaver 15 MPPT. Just to the right of that you can see a metal "hoop." That's a guard for the breaker that is on the incoming wires from the solar panels to the solar controller. It's mostly used as a switch so that the solar input can be cut off at will. Actually, I would have used a switch but for two reasons: One is that originally we were going to go with some used solar panels that were 24 volts each, and they were going to be wired in series. That would have been too many volts for the typical switch, but this breaker can handle higher voltages. In the end we elected to use a new pair of panels for size reasons (more compact), but we already had the breaker and it is physically smaller than a switch. It is rated to be used for switching. But it's a little easier to accidentally bump, hence the guard strip.
And that's basically it. There are a few wires that you can't see. A temperature compensation wire runs from the solar controller to one of the negative battery posts (just to measure temperature), and positive and negative wire for the Smart Gauge have to read directly from the battery posts. So much for only having one wire on each post
Heh, but at least the additional wires are small and really have to be there.
This setup doesn't have any provision for alternator charging, so you don't see any of those type of components or wire.
So the buses organize (plus there are labels on each wire under the loom) and allow for correct fusing. Basically for each load I took a few things into account to decide on the wire size. It's a spm:what circular process of checking one thing against another until they are all satisfied: What is going to be the maximum amp draw (or charge amps)? How long will the wire be (round trip)? How much voltage drop is acceptable (adding up all legs of a run, not just this one)? Then once a theoretical wire size is chosen based on that set of parameters, I consult an ampacity table and see what the maximum allowable fuse size is for that size wire. As long as that doesn't contraindicate what I came up with in the first answers, then all is good. Going down the line from batteries to components, whenever a larger wire steps down to a smaller one, probably a fuse or breaker needs to come into play to protect the new wire size (see ampacity table again). For example....
Let's say the main battery cables here are 4 AWG. So there may be a 100 amp fuse in the MRBF terminal on the battery post. Then at the positive bus, a smaller wire goes off to the inverter. If that smaller wire can't be fused at 100 amps, a new smaller fuse needs to be put in at that junction to cover the now smaller wire run heading off to the inverter. The wires to the LED lights are even smaller, so they, too, need to be fused with their own smaller fuses.
Of course on the typical Chinook, these functions are a bit more split up -- some things in the battery compartment, some at the brown box, etc. But the concept is the same.
I hope this wasn't too "off track" as a reply to your question (you know, the one you thought might be covered in a one-sentence reply
I just thought perhaps showing how one small system was organized (and this one was easy to show in just one photo) might help you to visualize a positive and negative bus vs. a cluster of wires (and fuses?!) on a battery post.
