Coach Batteries and Storage

[Blue~Go]

Still here. So, it looks like if I were to mount a busbar on the inside aft wall of the battery compartment for the positive cable hookups and the Blue Sea transfer switch on the other side of that wall (sort of a cable pass-thru), that would make for a tidy and secure install (Blue-Go ?).

I'm all for something along those lines, as I just hate battery posts with big clumps of cables coming off them! I can't exactly visualize where you are meaning to put the switch though (?). Here are some thoughts:

Okay, before I start, I know, project creep central. But I'll mention it anyway. Presuming you have those same "auto resetting" breakers I had... well, I think they are a bit chintzy. Also the wire to the Surepower isn't even fused (or wasn't on my rig).

I would be curious to see any other 2001+ Chinook owner's battery cable hook ups. As Blue-Go observed, mine seems to have been not so well re-connected. This most likely happened during the last few months when the rig was being upgraded at Duncan RV Center... AND when the new coach batteries were installed (sigh).

I know, that sucks, doesn't it? That's one reason I do most of my own work. I know there ARE competent folks out there, but they are hard to find and I can't always find them. To the good, now I understand my system and with the money I saved on labor I was able to buy top notch components without even giving it a second thought. NOT that I'm saying a competent electrician isn't a good thing, or that people should just start experimenting. But as we can see having things "professionally" done... isn't always. I helped a friend re-do his rig last winter, and the kicker was that he had had an RV electrical specialist re-do it once already. We found some rather horrifying things. OTOH, if I could always find that elusive true pro, I'd hire them in a heartbeat (well I don't need to now, but I would have). I know this is a bit to slog through, but as you can see, you may be your own best "pro" in this case. Even if you do hire work out, it's good to know what you should be seeing.

So anyway, here is what I would do. This presumes you are not changing anything "downstream" of the battery compartment (not that you shouldn't, but let's keep it below decks for now).

First of all, you have your two batteries. The wires should be connected as shown previously, with the negative and positives coming off "opposite" batteries. There is only the one negative (well, plus the solar wire, but that's tiny), so you might not need a bus bar there. It's never a bad idea though!

You have three big positive cables, plus the solar wire, so there I would go to a bus bar. OR, if you want to save a bit of space, you could use a power post. This would end up with a bit of a "pinwheel" shape of wires coming off, so a bus bar might be tidier. Also, this is the time to look at your fusing (OCP, or over-current protection; can be fuses or breakers). I'm going to make some assumptions on cable sizing and temperature rating - please let me know if I am wrong.

Okay wait, back to the big picture, it should ideally go like this:

Batteries
OCP (fuses)
Switch
Bus bar
OCP on any wires coming off bus bar that need different size fusing than wire leading into bus bar.
Then on to wherever the wires are going.

The reason the OCP comes right away is that that means there is little to no unprotected wire (that can chafe/short). Given that there is a sliding metal battery tray, I'd like to see this right on the battery.

So, here are my presumptions:

1) Two Group 27 batteries with a combined short circuit rating of under 10,000 amps.
2) Cables coming off battery:
a) 8AWG, 105ºC rated wire to LVD (and thence to loads/charger)
b) 6AWG, 105ºC rated wire to generator starter
c) 4AWG, 105ºC rated wire to Surepower and thence to Ford start battery.
d) Small wire (10AWG? 12 AWG?), 105ºC rated wire to solar controller.

Okay, lets look at fusing requirements. We fuse for the wire, but also that fuse has to be large enough to accommodate the load (if this can't happen, wire needs to be larger). We go to the ampacity tables. I will give the benefit of the doubt and go to the single wire tables (bundles are derated). That said, the 8AWG wire going back to the DC load center/charger is in a HUGE bundle, of maybe 10 wires, behind the upper couch cabinet - so this is giving it a bit more benefit than it deserves.

Wire "a," the 8AWG wire going to the load center/charger. We look in the left hand column for "8AWG" and then follow it over to the "105ºC" column. This is not going through an engine space, so we read the left hand one. It shows 80. This means the wire can handle up to 80 amps. This means you can fuse it to 80 amps (not that you have to). OTOH, this wire is in a huge bundle (i.e. traps heat). This means the wire is "de-rated." For bundles of 7-24 conductors, you multiply by .714. 80 x .714 = 57. So you can fuse up to 57 amps. If the wire is carrying less than 50% of its rating, you can not de-rate it. Confused yet? LOL

Anyway, your charger is likely a 45 amp charger and you are very unlikely to draw more than 30 amps at once in the other direction, so I'd probably put in a 50 or 60 amp fuse. Chinook used 50 amp breaker, so that's about right. I just don't like the type of breaker they used, and the placement isn't wonderful.

Next you have
b) 6AWG, 105ºC rated wire to generator starter

This wire is run alone, so no bundling worries. It does not pass through an engine space. So looking at the chart again, we see it can be fused up to 120 amps. I believe the generator starter draws ~60 amps. When Chinook had that wire on the starting battery, they used an 80 amp breaker and that seemed to work fine. So I would fuse that wire for 80 amps.

Next you have
c) 4AWG, 105ºC rated wire to Surepower and thence to Ford start battery.
This wire is a bit tricky. First of all, looking at the chart, we use the "eng" figure, because this wire does pass through the engine compartment (heat). So we see it can be fused up to 136 amps. And that is fine for carrying alternator current back to the house bank (we have something like a 120 or 130 amp alternator, but some of that amperage is always running the engine, so you won't get that much going back through the line.

HOWEVER. If you are also using that wire to "self jump start," then you have to consider the current the start will draw. From my research this is around 150 amps. There is higher inrush current, but that is only momentary, so doesn't have to "count" for fusing. So there are a couple of choices here:

1) You are technically "allowed" to fuse up to 50% over. So that means you could fuse at 200 amps, which I think will be enough not to blow.

2) You could use the self jump switch in another way, which would be to hold it down for awhile and let some of the current "seep" up to the start battery, then let it off and then start (at least I think the switch will allow that).

3) Carry an Anti gravity start pack and use that.

4) Carry separate jumper cables and use those.

What I did was run a larger wire between the start and house banks. That solved two things. One is that it eliminated the big voltage drop, so my alternator voltage reaches the house bank more efficiently. Two is that I can easily fuse to 225 amps, and do an "active" jump start with no worries. On the other hand, Chinook chose to not fuse that circuit at all (!) (at least on my rig), so at a minimum, if not wanting to change the wire, I think I would fuse it for 200 amps and then test it out to see if that is enough (to be correctly fused a fuse should also be added to that wire at the start battery).

And then
d) Small wire (10AWG? 12 AWG?), 105ºC rated wire to solar controller.

This already has an inline fuse. If wanting solar power to be "on" when battery switch is off, this should go on the battery side terminal of the switch.

So, if you want to do the fusing, how does that all fit in? This is where I wish I had a good way to make diagrams!

To summarize:

8AWG to LVD = 50 amp fuse (or 60)
6AWG to generator = 80 amp fuse
4AWG to start battery = 200 amp fuse (see discussion points above).
Small solar wire = inline fuse

Now one thing is that a bus bar and a bunch of fuses coming off it (which is what we did on my buddy's rig) takes up a fair bit of space. Not huge, but you have a small space there. I can see that what Chinook did on later years (but not on yours... right?) was to put in breakers for each of these lines. These cost a bit more, but they can make it sort of possible to not use the bus bar, if you'd rather go that way. Basically, there are a number of ways to make it work, but they all end up with the same principle, which is wires protected against shorts. The bus bar is very tidy and tidy looking, which is great, but takes up some space, especially with added fusing. ANOTHER way is to make your own bus bar, by busing fuses together, but let's not go there yet.

I'll make up a couple of drawings which might make it easier to see than the above nine-thousand words (if you are even still with me? ) This seems to sound very complicated in words, but it isn't really (really!).

[Blue~Go]

BTW, here is a photo of a 2006 Concourse. You can see that they have gone to breakers (and some other things that I can't tell what they are), with the associated wiring being "behind the scenes" of some sort of board. Probably it is an electrical improvement over the '99 era wiring, as that does not have all of the appropriate breakers, etc. Nice how they improved over time.

Here are a couple of drawings of ways you could change your battery locker setup if you wanted to. There are even more ways to skin the cat, of course. Either of these would do a few things:

1) Clear the battery posts.
2) Provide proper over-current (short) protection.
3) Allow you to switch off house loads (via switch or via breaker that is rated to be used as a switch).

It's all a matter of what you want to do and what "style" you like of accomplishing getting from A to B. There are things that should be done electrically (proper sized wire, proper protection), but in small spaces the physical layout often determines what course is best.

Also, some folks want a switch to only shut off the loads, but still allow solar power in, maybe still allow charging by the alternator, and still allow generator charging (although the way the Chinook is wired you'd have to switch on the loads to get charging to the batteries due to their dual purpose use of one wire). I showed it the latter way, with the switch only cutting off the loads, but there are other ways to do it.

An improvement would be to run a larger wire more directly to the charger/load center. But that's an additional task. That would reduce the crazy amount of voltage drop they have, and possibly allow you to skip a fuse (depending on what size wire you run).

Or you can just disconnect the battery leads for now and be done with it. But I would MOST definitely move that incorrectly placed positive cable. That's not good.

In drawing A, the breaker is also the switch for the load center. In drawing B there is a dedicated switch, but then fuses or breakers of some sort still need to be provided (that's the "S" shaped symbol).

[Blue~Go]

Now maybe you're sorry you asked?

[HoosierB]

Thank you, Blue-Go! You have provided an education on RV electrics for sure. For now, I will definitely reposition that cable and just disconnect for storage. The storage facility does not allow any "work" to be done on rigs when in storage, so this will give me time to digest my next move on the project. This drawing shows what I'm thinking of doing, not sure yet how/where to include "fuses" if I have the room. Would this work in the meantime?

[Blue~Go]

Well I'm really glad it was helpful and not just totally confusing or too much information. And I can see I need to step up my computer drawing program capabilities!

I think your plan of moving that one positive cable to the "correct" post and then simply disconnecting things over the storage period is a really good one. Simple and gets the job done. And as you say, if you can't work in the storage facility, you might as well spend some time over the winter noodling what you really want.

I think if it were me, I'd sort of mentally step back and ask myself how I would like to use the rig, and what I'd like to "get" from the electrical system. And then make a plan. For example, I had mentioned that load/charge wire in passing (that is the #8 that goes from the house batts to the LVD, then up the pillar, through the overcab, along the wall above the window, down the shower wall, around the corner, and then through the kitchen sink cabinet base to the brown box. Yes, another ten feet or so and it could circle the earth! This means that any specific voltage that the charger is putting out is considerably diminished by the time it reaches the batteries (voltage drop). Of course that original charger isn't too specific anyway, but I think you see where I'm going with this.

The "little wires" in the Chinook are very serviceable, and they are all fused for their size. So except for any specific things (such as "I really want a 12-volt outlet by the table") I think they can be left as is. But... there are some issues with the "big" wires. Not that Chinooks are burning down right and left, but I see deficiencies in three areas:

1) Some wires are overly long/overly thin and lead to a lot of voltage drop.
2) Some wires are not properly protected against shorts (fuses/breakers).
3) Some wires are not well organized (big clumps on battery posts, etc.)
4) Some functions may not be doing what you want, depending what you want (charger killing house bank; solar too small for use case, etc.)

None of this is really a rap on Chinook. Compared to most RV's I've seen they did a decent job. And they covered a specific use-case ("we used to have a Class A; now we want to do the same things in a smaller rig"). Also, the state of things at the time was different (solar panels cost a mint, chargers weren't "smart," etc.).

When I say use case, I'm sure you probably know what I mean, but just to list a few:

1) Days spent either driving or plugged in. Maybe one overnight in a blue moon in a Wal-Mart parking lot.
2) Driving or plugged in most of the time. But I'd like to be able to spend a long weekend boondocking.
3) Plugged in? What is that? Boondocking 24/7 is the goal.

The other thing is what does one want to run? Scenario #3 could mean that the boondocking would include the microwave, air-conditioner, a hair dryer, a desktop computer - basically all the comforts of home. Or the same scenario could be done by a person who basically wants a "hard tent." Laptop computer, LED lights, propane cooking, and catalytic heater. Different setups for each.

Okay, now back to your drawing (sure glad one of us can make tidy drawings!). I made a couple of mods and am going to repost it here, with some commentary below it.

So, what did I change, and what else might you want to noodle over the winter?

What I changed:

1) I added the negative (ground) wire coming off the upper house battery. Maybe you just weren't showing grounds though.

2) You had two positive wires coming from the LVD but there is only one that goes from the LVD to the batteries. The second wire that comes off the LVD goes up the pillar and over the window and then to the "brown box" under the sink counter.

3) I added a wire going to the start battery (via the SurePower). That was missing.

So okay, add negative cable from upper battery, remove "extra" wire from LVD, and add wire to start battery. Done, right? But wait, there's more!

So now the way it's set up in the drawing, when you turn that switch off EVERYTHING is off. And this may be just what you want. But, for example, if you have the rig parked in your driveway, and the switch is off, no solar top-up power is going to your house bank. Because that positive solar wire goes to the switched bus. I also think you wouldn't get any power to the batteries via the charger. There is also no connection between house and start battery (alternator charging) when switched off. Which may be fine with you. But just so you know. And that IS one variable that is a decision point. Do you place the switch so as to cut off all loads AND all power sources? Or do you place it to cut off all loads but allow power sources to remain connected? Or do you pick and choose (cut off all but solar input, etc.). There are plusses and minuses either way - just depends on what you want, and that you know what's happening. One can also have it "both ways," but putting in a switch as you show it - cutting off everything so batteries are completely isolated - and also using a switch-rated breaker on the wire to the loads (then you can flip that breaker and cut off loads, while leaving switch on to allow charging sources in; OR you can flip the switch and cut everything off).

There is one other possible "thing" - no need to really worry about it at the moment but I'll just mention it. That is that Chinook used one wire to do double duty: The #8 red wire that goes from the batteries to the LVD to the brown box. That wire can carry power from batteries to loads, and it can also carry power from charging sources to batteries. That's why there is a light and buzzer by the "store" switch. Because say you have that switch off ("store") and you fire up the generator. No power can get TO the batteries because you cut off the load wire and it is also the charger wire. So Chinook has a light/buzzer to tell you to turn that switch back on. When I re-wired I put in one wire for loads, and another wire to the charger, so these functions no longer share one wire. It can work either way; just something that's good to know.

Oh and I forgot to mention OCP (over-current protection, i.e. fuses or breakers). These are used so that if there is ever a short (which you try to protect against, but which can happen, especially in vehicle that moves) the fuse blows instead of the wire likely causing a fire. As was shown in the chart before, each wire size can handle a certain number of amps before melting down, so you put in a fuse that is just smaller than that. That allows the wire to do the job without the fuse blowing, but the fuse will blow if there is a short.

So, a system starts out with big wires (at the batteries, for example), and you fuse those with bigger fuses (wherever I say fuses, one could also use breakers). Any time a wire gets smaller, then the previous fuse is likely no longer protecting it, because it's too large. It's like if you had a certain size seive for boulders, but then you put grains of sand in instead: If you don't make the seive mesh finer, the sand grains will all fall through. Fuses and breakers can be a bit "messy" to fit in small spaces, so sometimes I will carry a larger wire size a bit further, just to keep things tidy.

As is, the Chinook has protection in some places but not others. I like it everywhere, so I add it when I'm re-doing something. Some things are easy, such as MRBF fuses right on the battery posts if your bank is not too large for them (yours isn't). But essentially, every wire should be protected by a fuse. One fuse could protect the entire rig if the wire was the same size everywhere. But since it isn't, one has to re-fuse (smaller "mesh") when wire changes to a smaller size. One example of this is all the small blade fuses in the brown box DC load area. One #8 wire comes in. That would be protected by a ~50 amp fuse (if you used a smaller fuse it would not handle the loads on that wire). But then you have a bunch of #12 and #14 wires going out to the various loads in the rig. They would melt down/catch fire long before a 50 amp fuse would blow, so you fuse them with smaller fuses that are appropriate to protect them. Hence the group of 10/15/20 amp fuses there in the brown box.

[caconcourse]

Thank you, Blue-Go! You have provided an education on RV electrics for sure. For now, I will definitely reposition that cable and just disconnect for storage. The storage facility does not allow any "work" to be done on rigs when in storage, so this will give me time to digest my next move on the project. This drawing shows what I'm thinking of doing, not sure yet how/where to include "fuses" if I have the room. Would this work in the meantime?

house-batteries-diagram.jpg

Hi HoosierB,

Just one last warning before your rig is inaccessible. In my Concourse, and probably all of them, the house radio (in the back) is powered by the starter battery for some reason. Make sure the radio is totally off (it might still draw some power to keep presets, etc.), or you can remove the cable from the back of the radio. It would probably last through the winter, but some have reported a dead battery after storage traced back to that circuit, which I think is shared by the engine computer, resulting in mysterious troubleshooting activity.

Clay

[Blue~Go]

Good point, Clay. My original coach radio was the same way. The reason why is that car stereos have two power wires. As I understand it, one is permanently "on" so that it can save presets, etc. when you shut the car off. The other is the rest of the power and comes on and off with the car or when the radio is turned on and off (when it's mounted as its meant to be, as an in-dash stereo in a regular vehicle).

If Chinook put both of the power wires for the coach stereo on the house power, then when you put the vehicle in "store" I think the presets and etc. would go away and the radio would do its whole new startup theme again each time.

I did change mine (was inspired by Bob Will's write-up) so that the coach stereo is totally powered by the house batteries. It was not a very hard job (just had to reach up into right hand "VCR" compartment and change a couple of wires). It is of no consequence to me if the presets are lost when I store the rig. And more importantly, I didn't want the radio drawing off the start battery while parked! So that is an option.

If it were me, rather than remove a radio wire, I'd just take a cable off the start battery. That would also keep any other parasitic loads from drawing down the start battery. But the main point is, as you said, not to have the coach radio drawing for months on the start battery, unknown. I'm not sure how much it draws, but something.

Another approach would be to shut everything off and put the switch in the store position (and/or remove cable from house battery) and then measure across the terminals of the start battery to see if there is any draw. If not, then it's not a problem to keep start battery connected. The draw may be miniscule (after all, you can park a car for months typically).

[HoosierB]

Just to confuse myself more... here is the electrical systems diagram from the manual (2000). It shows a neg cable coming off the coach bats going to both the solar panel and generator. No pos cable going to the gen. It also indicates auto resetting breakers for the pos cables before the LVD input. And a pos cable coming off the far left bat to the Smart Solenoid. Would adding more "fuses" be really necessary? I'm assuming that the way some of the cables are bundled inside the black plastic loom, they eventually get to the destinations indicated on the diagram... My brain hurts...

[Blue~Go]

Your 2000 is very similar to my 1999, and I've been "inside" all of the wiring. Let me make a couple of comments:

First of all, that generator cable showing as a negative is simply a mistake. But it does show me why you kept putting a black generator wire on your diagrams! You were just reading the Chinook manual. The negative part of the generator start circuit (that's all this wire is - power to start the generator) is just a short lead to a chassis ground. It is the positive (red) cable that goes to the battery for starting power. That is not in doubt at all (meaning, if something is in doubt, I'd say so). Here is how I think they made the mistake. See the 1998 diagram, in which the generator start positive wire goes to the start battery (note it goes to the POSITIVE terminal)?

This is the same on the 1999 (my year) but I don't have that manual digitized. Then in 2000, they decided (for good reasons, IMO) to move the generator start positive wire to the house bank. You can imagine how they modified the drawing, and....oops!.... took the wire to the negative post by mistake (in the drawing - in real life we can see that it's the "third" positive cable on your house bank). The next manual I have is 2004 and they no longer give us the DC system sketch at all, from what I can see.

So, to re-draw the 2000 manual sketch, it should look like this. There should be an 80 amp breaker in there somewhere (on my rig it was on a bracket near the start battery since the wire went there; you must have one somewhere, I'll get to that in a minute). I made the new "wire" red to make it more obvious. I don't show the breaker, we'll get to that next.

[Blue~Go]

So okay, OCP (breakers and fuses).

As mentioned before, they are to keep things from melting/burning down if there is a short in a wire. A short will cause all of the potential power in a wire to come "pouring in" all at once. This is bad. For example, your house bank is a nice little power storage facility. If a wire shorts to the frame somewhere underneath, all that power goes "whooshing out" all at once, overwhelms the wire, and a fire can start.

But every wire size can handle "X" number of amps WITHOUT causing a fire. So we put OCP on that wire in the form of a fuse or breaker. Let's take the wire that goes from house bank to start battery, for example. Say we look up the wire size and see that it can take something like 150 amps (just taking off top of my head to illustrate point). But if there is a short, MORE power can go into the wire and cause a fire. And let's say we only need 100 amps in normal circumstances. So we can fuse the wire at 125 amps, and carry on our normal business with no problem, yet if a short occurs and a large number of amps try to "flood" the wire, the fuse will blow. Disaster averted. This is the point of OCP (over-current protection).

If you have a wire coming off a battery and the fuse is right there, the whole wire will be protected from that potential power. If the fuse is two feet along the length of the wire (away from the battery/power source) then the first two feet is NOT protected, but the rest is. So the closer you get the fuse to the power source, the better. This is why I like MRBF fuses. They are ON the battery post. The whole wire is protected and you don't have to find a "place" to put a fuse.

I don't know how your rig is set up physically, but I can see on the drawing that it has the same 50 amp breaker on the main wire to the charger/loads. Amp wise, 50 is a fine number for this wire. There are two potential issues. One is that you have four feet of wire between the battery and the fuse (at least mine did; they were in a little white fiberglass "cup" under the rig, ahead of the battery box). That is foru feet of unprotected wire in a sliding metal battery tray that then goes through a hole in the "wall). What could possibly go wrong? (Chafing, short...) The other thing is that we now know there is such a thing as AIC (Ampere Interrupt Capacity). To say it simply, this is the rating of the fuse body itself. It doesn't do much good to have a 50 amp fuse (say) if the short melts the fuse body into a solid "wire" before the fuse can blow. Hence we have AIC ratings on various types of fuses. My guess is the 50 amp breaker Chinook used is not rated high enough or not rated at all (not that I have checked). Just as an example, I have 375 amp hours of house batteries. BUT the short circuit rating is over 12,000 amps (power they can exude if there is a short). Ow!!!!. So I couldn't use the MRBF fuse as they are only rated to 10,000 amps. I have no doubt the original 50 amp breaker was underrated as well. I used a Class T fuse which is rated to 20,000 amps. I still use a 225 amp fuse (appropriate for my 1/0 wire size). So AIC and fuse size are not the same. With your smaller battery bank, you COULD use the MRBF fuses. Super convenient and protect the WHOLE wire.

So the four positive cables you have coming off the battery:

1) 8AWG to charger/house loads. Fused with a 50 amp fuse but leaves around 4 feet of wire unprotected. Fuse may not have high enough AIC rating. Fuse is auto-resetting. I would rather have it blow and need to be reset or replaced manually so I can immediately track down the problem.

2) 6AWG (in my rig) to generator starter. This has an 80 amp manual reset breaker in my rig. This is adequate. It was very close to the battery in my rig. Not sure where it is in your rig - maybe in the white fiberglass "cup" underneath with the 50 amp breaker for the charger/house loads? Easy to look. If so, it's leaving around 4' of wire unprotected.

3) 4AWG (in my rig) wire to Surepower and then house battery. Not fused AT ALL in my rig, on either end (until I changed it). I wasn't comfortable with that. I think one reason it may not be fused is that 4AWG is a bit small for the "jump start" feature, and if they fused it properly the fuse might blow when you jump started. OTOH, the wire doesn't melt during the short duration of a jump start. On the other hand it is unprotected against shorts 24/7. There are a few options to ameliorate this, but I won't mention them now so your head won't explode.

4) Solar wire which is around 10AWG, IIRC. That has an inline fuse close to the battery. I'd still rather have it behind a good fuse (MRBF etc.) (Once the first main fuse is high enough AIC rating, the rest after that don't have to be, as it would blow first.)

I'll dig up a couple of pictures of where my 50 amp fuse was so you can see if you have something similar on your rig. From the drawing it looks like it's about the same, although I would hope to see the 80 amp generator start wire breaker somewhere in there as well (mine was under hood as gen start went to Ford start battery).

One more thing: All wires don't need to be fused at both ends. They need to be fused on any end that can "put out" power. So for example, the wire that goes from start battery to house battery needs a fuse at both ends, because both ends can "put out" power to a short. The generator start wire only needs a fuse at the battery end, because the generator doesn't put power into that wire (it's only to the starter), but the battery does. (The output of the generator is 110 volts and travels in a Romex type AC wire not through the DC wire.)