Batteries and wire gauge questions

[vigilante]

I had to replace the batteries in the RV. It looks like it originally had one battery, but was later upgraded with two. I bought two matching new ones.

The old ones were flooded type batteries only a year and a half old. 3 cells were completely dry and one cell the liquid was muddy colored. I tried to fill up one battery and put it on a charger for a couple weeks. It came up to voltage but quickly died being off the charger again for a day.

Anyway, I bought the new batteries which are sealed and not flooded. I'm hooking everything up and found some issues like frayed wires, one white wire completely snapped, barely saw that one. And looks like they monkey patched a few leads in there as well. The colors don't match the official color standards.

So my main question is this. They previously had a battery shutoff switch connected to the positive. I went ahead and bought a new switch. The main lead off the battery is 2gauge wire, but the wires coming off the RV are much smaller, like 14ga looks like. So if I have 2gauge from the battery into the switch, what do I use from the switch to the 14guage terminals from the RV?

I'm kind of confused why I would use such large gauge wire off the battery and then simply drop to 14ga. I've noticed a lot of the wires in here have a dull grey color rather than the copper wire color. I think there must have been some overheating or something to cause this, maybe just oxygenation?

If the RV positive terminals and junctions all use 14ga wires, why do I need a battery shutoff switch that apparently uses such high gauge wires off the battery?
And even if the 2ga wire is correct, the very large post terminal crimped on the end is way too large for the little bolt and nut from the RV terminals. Do I just use some adapters? It just seems strange to me. I wish I had a picture of the original setup but I don't.

I'll try to post some photos after this message.

[vigilante]

Here is an image with batteries out. You can see the battery tray, it was designed for one battery I guess, unless the tray was added later?

I guess I can see now there are mixed wire gauges being used in here, including a larger one from that first junction box. I'm guessing the shutoff switch I should use a gauge at least matching that one. But how do I get such a large gauge wire with such a small post connector?

Help me make sense of this!

[JRTJH]

First, I'd ask:

What trailer brand, year and model do you have?
There is a BIG difference in the electrical wiring in a 2005 17' travel trailer with no slides and a 35 amp converter/charger and a 2021 43' toy hauler with solar, domestic refrigerator, three air conditioners, hydraulic slides and leveling system, powered by a 100 amp converter/charger, all controlled by an "In-command system with blue tooth remote.

In your photo, the "junction boxes" you refer to are actually DC automatic reset circuit breakers.

Depending on the trailer "year/model" the battery cutoff switch may not be OEM parts, but aftermarket parts.

Is the trailer "new to you" or are you the original owner? If previously owned, what did the original owner do to modify/change the electrical distribution? If OEM, did the dealership modify/change the distribution system to include/add/modify installation of any items added at the customer request? I've seen a large number of "initial delivery" trailers with add-on solar systems, add-on inverter systems, add-on generator transfer switches designed to be used with a stand alone generator and lots of other "owner requests" that were done by the dealer "to make the sale happen".

So, what are we dealing with in your situation? and finally, is everything working as it should and you just want to "clean up the mess" or is there a problem with the wiring and you're troubleshooting the issues????

Help us help you.

[flybouy]

I'll try to explain some of this.

The wire size from the battery to the switch must be sized to carry ALL the loads simultaneously. So let's say you have 3 30 Amp circuits then that wire to the switch and the battery ground must be capable of a minimum 90 amps.

The "Terminal blocks" are actually self resetting circuit breakers. They should be stamped with an amp rating.

Wire size terminals. They are available in caring wire sizes and ring sizes. I.e. Let's say you have 10 GA. wire and the stud is a 1/4". Then you look for a 1/4" ring terminal for # 10 wire.

The "gray" colored ground wire. With any copper wire it should be bright shiney copper color. Anything else is an issue. Strip it back to good wire or replace it.

You don't give us any info on the trailer like make, model & year. Your description of the 2 new batteries is vague as well. A "maintenance free" battery may be sealed and is typically still a flooded cell, lead acid battery. Did you get 2 12v or 2 6v batteries? What's the brand and type battery? The more info you share with us the better the advice and recommendations will be for you.

[vigilante]

Thanks for the replies.

I have the make/model in my profile but I guess that's not easily accessible, I'll add it to my signature.

This is "new to me", from a 2nd owner who stayed in it about 6 months from the original owner.

2011 Laredo 321BH, it's a 36 footer with 3 slides. I honestly can't find a ton of info specific to this model as it seems the user manual covers every model from that year.

There is nothing fancy/extra on this, no solar, it's 1 A/C (we will want to put in a 2nd eventually), 3 slides, front and rear power stabilizers.

It seems obvious to me they added the 2nd battery as well as the shutoff switch. It was not installed with any factory precision, really just flopping around back there loose, not screwed to anything, cables cut too long, etc.

New batteries are a WindyNation pair.
https://www.amazon.com/gp/product/B07BRND6MF/
I don't care if these are low quality or whatever, I did some research first to try and avoid terrible batteries at least. Mainly I just had to get something to "make it work". Eventually we'll save up for lithion ions but this will have to do for now.

I want to properly set up the two new batteries, as well as "do it right" if they tinkered in here and did something wrong. The previous owner is a manufacturer of car stuff, so you'd think they could do this right, but actually I had no less than 4 crimps simply come undone by wiggling. Probably why some of the wire turned grey. Connections at the junctions also had loose nuts.

So if I'm reading you all correctly, I could do perhaps 4ga off the battery into the switch, and probably 4ga again to that first junction? As the junction itself has 6ga going off to the next one.

I'm only worried about such a large wire going down to such a small post/nut on the junction. But if it's meant to carry that much power? What do I know?! Or maybe 4ga or even 6ga is way overkill on the battery switch in the first place?

I have no info on what the previous owners did. I assume they did nothing. It kind of looks like an "I did nothing" RV, except of course for adding 2nd battery and messing with stuff.

[GaryUT]

Originally Posted by vigilante

here is an image with batteries out. You can see the battery tray, it was designed for one battery i guess, unless the tray was added later?

I guess i can see now there are mixed wire gauges being used in here, including a larger one from that first junction box. I'm guessing the shutoff switch i should use a gauge at least matching that one. But how do i get such a large gauge wire with such a small post connector?

Help me make sense of this!

I labeled 3 terminals in your photo A B and C. These are all terminals on auto resetting breakers.

Positive power is daisy chained from one breaker to the next.

A is where the cable from the cutoff switch should be connected. Terminal A has a wire going to terminal B and a blue wire, the blue wire is normally the break away switch power.

Terminal B has 3 wires, one going to terminal A, the other to terminal B, and one going to a fuse holder for something that was most likely added to the trailer.

Terminal C is connected to terminal B.

Ideally the negative battery cable should be grounded to the frame with all the other ground wires that are on the screw. On my trailer I added a buss bar with the negative battery cable connected to one end and the other end grounded to the frame. this gave me better places to connect ground wires.


Gary

[GaryUT]

Looking at your photo again the breaker that has the terminal I labeled as A needs to be replaced. The mounting ears are broken off. I looks like it was mounted next to the second breaker, the screws are still there.

As far as wire gauge goes it needs to be sized for the fuse that is protecting it. Most trailers don't have a main fuse protecting the battery cables, so keep them short and well protected.

I added a terminal fuse to the battery cable on my trailer. The trailer has 6awg battery cables so I used a 100 A terminal fuse.

Gary

[vigilante]

Thanks Gary, I think you are correct on all counts.

The orange wire with the inline fuse disappears into the sidewall somewhere behind the propane and storage. My guess is maybe the rear power stabilizers which I now wonder if they were original.

I'll check the rating on the junctions and probably just replace all three at the same time.

I can't tell the amp rating needed for each junction/fuse. There is a fuse box in the RV with about 15 fuses in there, most are 15amp but there are a couple 20s and even one 30 in there.

Now the problem is I don't have all the wires/colors/gauges and appropriate crimp ends and heat shrink to fix it all. I've look for kits and will have to figure something out. There is at least 4 or 5 different gauges at work in here, and multiple colors I want to remain accurate since this does have a wire color standard in use.
My local Home Depot and Lowe's don't even carry any kind of crimper for 6ga or larger.

[JohnP]

Since we are on battery topics I have a querrie: Last fall I installed a second battery and a battery shut off/turn battery "A" on/off battery "B" on/off. Everything works fine but I see in stores they sell battery isolators. Kind of an aluminum looking heat sink type of unit. Do I need one and what is its purpose ? What if I don't install one ? Thanks for any info in advance !!!

[flybouy]

Originally Posted by JohnP

Since we are on battery topics I have a querrie: Last fall I installed a second battery and a battery shut off/turn battery "A" on/off battery "B" on/off. Everything works fine but I see in stores they sell battery isolators. Kind of an aluminum looking heat sink type of unit. Do I need one and what is its purpose ? What if I don't install one ? Thanks for any info in advance !!!

A battery isolator is basically to keep one battery from draining the other battery while charging both from one source. Typical use would be two batteries in a boat. You can have one battery for operating a trolling motor, lights, etc. while not draining the second battery that's reserved for only starting. That would be used in a system with everything wired to each battery but no ability to use both at the same time. It is not necessary in a trailer if the purpose is to use 2 batteries just for the extra capacity.

[vigilante]

Ok riddle me this one.

So I checked on the three self-resetting breaker junctions. The 1st one that was connected to the battery, is 30amp. But the 2nd one in the chain, is 50amp!

Unless I'm missing something, how could the middle one draw anywhere near 50amp if the 1st one is only 30?

The 3rd one has a brass coloring to it, not like the other two with black plastic, and there are no markings that indicate the rating that I can see. Is there some other way to tell?

If this seems wrong to you too, my brain is telling me the first junction should be the 50amp and the middle one 30amp, and likely the 3rd one is 15 or 20, maybe even 30 again.

Also, that random orange wire has its own inline fuse which is 30amp if I remember. So the that could certainly be put in the 50 or 30 junction, but I think if that 50amp middle junction draws anything above 30, it would trip the first one anyway.

It just seems wrong to me. Should I rewire the junctions to put the 50amp first, to the battery, and then the 30 after it? Or could it be possible that the battery originally connected to the "middle" junction in the first place?

I really just need a schematic or something how this RV was originally wired. arg!

[flybouy]

The wires should run from the battery positive cable to the battery terminal on the first fuse. Then from that post go to the second fuse battery post, then from that post to the next fuse battery in post. The other posts are the fused side or the load side. It's a parallel connection not a series connection.

[vigilante]

Originally Posted by flybouy

The wires should run from the battery positive cable to the battery terminal on the first fuse. Then from that post go to the second fuse battery post, then from that post to the next fuse battery in post. The other posts are the fused side or the load side. It's a parallel connection not a series connection.

Sorry but that isn't very clear to me. Did you see the pictures above? There are three self-resetting junctions. Battery connects to 1st one which is 30a. The 30a then connects to the 2nd one which is 50a. The 50a then connects to another mystery one.

My question is, why would the battery positive first connect to a 30a, then chain to a 50a? How could the 50 ever pull near 50 before the 1st one trips at 30? It seems like they are backwards to me.

I've been trying to find diagrams but so far none of them show that these self-resetting junctions are even used in the first place, making me wonder if this is all aftermarket stuff.

Here is a crude diagram of what I've got going on.

I would also add one more oddity. When I connected the batteries, but not using the cutoff switch yet. I was getting zaps at the positive terminal. I left it disconnected for now. I had the 50A shorepower unpluged, all breakers off. I'm not sure why I would be getting zaps at the battery if there should be no loads going on. Or would getting a few zaps as I connect it normally anyway?
Are there still loads from the system even with shore and breakers off? I was afraid there might be a short or something, I didn't want to force it and clamp down the wire without knowing why it was zapping.

[flybouy]

Originally Posted by vigilante

Sorry but that isn't very clear to me. Did you see the pictures above? There are three self-resetting junctions. Battery connects to 1st one which is 30a. The 30a then connects to the 2nd one which is 50a. The 50a then connects to another mystery one.

My question is, why would the battery positive first connect to a 30a, then chain to a 50a? How could the 50 ever pull near 50 before the 1st one trips at 30? It seems like they are backwards to me.

I've been trying to find diagrams but so far none of them show that these self-resetting junctions are even used in the first place, making me wonder if this is all aftermarket stuff.

Here is a crude diagram of what I've got going on.

I would also add one more oddity. When I connected the batteries, but not using the cutoff switch yet. I was getting zaps at the positive terminal. I left it disconnected for now. I had the 50A shorepower unpluged, all breakers off. I'm not sure why I would be getting zaps at the battery if there should be no loads going on. Or would getting a few zaps as I connect it normally anyway?
Are there still loads from the system even with shore and breakers off? I was afraid there might be a short or something, I didn't want to force it and clamp down the wire without knowing why it was zapping.

Attachment 31660

I can't answer WHY yours is wired incorrectly (according to your diagram) but am trying to explain how it SHOULD be connected. Every camper I've ever seen is wired this way using the same or similar circuit breakers wired in parallel being fed by the battery positive cable..

The only way there should be two circuit limiting devices in series is if the first one is of sufficient value to carry the current of the second one. As far as your "zapping" goes, until either you, or a qualified tech get's the wiring corrected anything is possible.

[bobbecky]

This is how those three 12 VOLT DC BREAKERS, not junctions, should be wired, and that's why it doesn't matter where the different amp rated breakers are positioned, and it's also why you have a large cable coming from the batteries.

[JRTJH]

Originally Posted by vigilante

Sorry but that isn't very clear to me. Did you see the pictures above? There are three self-resetting junctions. Battery connects to 1st one which is 30a. The 30a then connects to the 2nd one which is 50a. The 50a then connects to another mystery one.

My question is, why would the battery positive first connect to a 30a, then chain to a 50a? How could the 50 ever pull near 50 before the 1st one trips at 30? It seems like they are backwards to me.

I've been trying to find diagrams but so far none of them show that these self-resetting junctions are even used in the first place, making me wonder if this is all aftermarket stuff.

Here is a crude diagram of what I've got going on.

I would also add one more oddity. When I connected the batteries, but not using the cutoff switch yet. I was getting zaps at the positive terminal. I left it disconnected for now. I had the 50A shorepower unpluged, all breakers off. I'm not sure why I would be getting zaps at the battery if there should be no loads going on. Or would getting a few zaps as I connect it normally anyway?
Are there still loads from the system even with shore and breakers off? I was afraid there might be a short or something, I didn't want to force it and clamp down the wire without knowing why it was zapping.

Attachment 31660

Looking at the photo you posted in post #2, the battery cable is attached to each of the mini-breakers "on the same end". They are not "daisy chained" (in series). In other words, unlike the drawing you posted in post #13.

In your drawing, the battery cable connects to the + on the first mini-breaker and then the - pole on that one connects to the + on the next, and down the line. The photo in post #2 is not wired that way.

In reality, according to your photo, and like Marshall stated, the battery cable connects to the + on the first mini-breaker, then is also connected (by a jumper cable) to the + on the second mini-breaker and from the + on the second one, it jumpers to the + on the third breaker. ALL of the + poles are connected to the battery and ALL of the load cables are connected to the - poles on each of the three mini-breakers. It's the way bobbecky drew his diagram.

They are not "in series down the line" but are "in parallel with all the + poles connected through battery cables. In this arrangement, each mini-breaker provides "protection to the individual loads connected to ONLY that mini-breaker and they all are "independent" from each other, with the exception that they are all connected to the battery + terminal.

Think of the attachments at the mini-breaker + poles the same as if all three wires were twisted together with a large "wire twist connector".

[Dallasrules]

This might be a stupid question, but shouldn't the battery disconnect be on the negative terminal?

[bobbecky]

It really makes no difference. As long as the circuit is open, no current will flow.

[apachewolf]

Originally Posted by Dallasrules

This might be a stupid question, but shouldn't the battery disconnect be on the negative terminal?

I always use a master disconnect on the NEGATIVE side, that way all power is disconnected, no guessing about "phantom" loads draining the battery when you think it is disconnected. In car service you always disconnect the negative first to ensure total disconnect.

Happy camping.

[LHaven]

Originally Posted by vigilante

My question is, why would the battery positive first connect to a 30a, then chain to a 50a? How could the 50 ever pull near 50 before the 1st one trips at 30? It seems like they are backwards to me.

These aren't necessary what the factory put in. They are more or less consumables, and often replaced by owners when they pop. With two previous owners, perhaps one of them replaced one of the breakers with the wrong size breaker. May have been responsible for daisy-chaining them, too, as they should be in parallel.