Shunt location on travel trailer with batteries in front

[Leo3]

1. What are you changing? I may have assumed more changes than are actually going to happen.
2. Is the 12v disconnect switch inside or outside?

After looking at the picture of your trailer and rereading the thread I'm thinking that much of what I've posted is overkill.

I'm adding an AiLi BMS from Will's website. That's it right now. I started with a 100A but switched to 350A shunt because I was worried 100 wouldn't handle it 100%.

The 12v disconnect switch is outside. I pulled some coroplast off so now I see where the wires come from that are going into the disconnect, and I can see where it's going out of the disconnect (which is directly to a 100A fuse and directly into inverter from there).

Don't worry! You gave me confidence to dig into it further. I want to learn and I want to do it right. Check out my post I just did w/ some pics and a little vid.

 

[chrisski]

Green usually means a common ground. I would bet if you traced one of those wires, it would go back to the frame, probably the thickest point. I see these for sale in Home Depot in the electronics aisle.

 

[HRTKD]

The bus bar with the many white wires and green screws is your negative bus bar. The big black wire on the right should be the lead coming from the battery. If you connect that lead to your shunt and then the shunt to the bus bar you'll be able to measure your state of charge.

In your second picture, the big red wire on the left should be the lead coming from the battery. This is your positive bus bar and that has to be the screwiest thing I've seen on a trailer. I believe those are self resetting circuit breakers.

It's kind of hard to tell what's what from the pictures.

It looks like someone sprayed the entire positive bus bar with battery terminal protectant. They must not have thought it was going to stay dry?

 

[HRTKD]

I'm adding an AiLi BMS from Will's website. That's it right now. I started with a 100A but switched to 350A shunt because I was worried 100 wouldn't handle it 100%.

The 12v disconnect switch is outside. I pulled some coroplast off so now I see where the wires come from that are going into the disconnect, and I can see where it's going out of the disconnect (which is directly to a 100A fuse and directly into inverter from there).

Don't worry! You gave me confidence to dig into it further. I want to learn and I want to do it right. Check out my post I just did w/ some pics and a little vid.

It's really called a BMS? When we say "BMS" around here we mean a Battery Management System that is connected to LiFePO4 cells. A lead acid battery doesn't need a "BMS".

 

[Leo3]

Green usually means a common ground.

Which green thing are you referring to? The really thick green wire I've noticed is wired to all the inverter powered outlets so I think it's dedicated to that. I think it's Romex.

 

[Leo3]

It looks like someone sprayed the entire positive bus bar with battery terminal protectant. They must not have thought it was going to stay dry?

You are exactly right it's all over that bus bar. It is underneath the trailer which is covered very well with the black coroplast. The coroplast is on there tight and spray foam has been generously applied in all the spots where, for example, wire enters and bows the coroplast to create small gaps.

 

[Leo3]

It's really called a BMS? When we say "BMS" around here we mean a Battery Management System that is connected to LiFePO4 cells. A lead acid battery doesn't need a "BMS".

No it's not. You're absolutely right it's "Battery Meter" or "Battery Monitor" I guess? It's here and on Will's site here.

 

[Leo3]

In your second picture, the big red wire on the left should be the lead coming from the battery. This is your positive bus bar and that has to be the screwiest thing I've seen on a trailer. I believe those are self resetting circuit breakers.

Okay here's that pic. I'll try do so some more tracing on it. I have three wires running into my disconnect (two shown here and one from battery) and one coming out of the disconnect (to a 100A circuit breaker then to inverter).

 

[Leo3]

The bus bar with the many white wires and green screws is your negative bus bar. The big black wire on the right should be the lead coming from the battery. If you connect that lead to your shunt and then the shunt to the bus bar you'll be able to measure your state of charge.

So if you look at the diagram of the trailer in an earlier post, this neg bus bar is behind the dist panel, not close to batteries. Not nearly as close as the pos bus bar. Is that normal? I will try to trace that black wire. When I was studying the wires up front I did not see any black wire that went toward the rear. Thank you!!

 

[HRTKD]

So if you look at the diagram of the trailer in an earlier post, this neg bus bar is behind the dist panel, not close to batteries. Not nearly as close as the pos bus bar. Is that normal? I will try to trace that black wire. When I was studying the wires up front I did not see any black wire that went toward the rear. Thank you!!

For what it's worth, my OEM negative bus bar is also behind my main distribution panel. They didn't even bother securing it down. It's just flopping around.

 

[chrisski]

Which green thing are you referring to? The really thick green wire I've noticed is wired to all the inverter powered outlets so I think it's dedicated to that. I think it's Romex.

Chassis Grounding is what I've seen it used for. I was looking at the terminals. This is what I see in home depot

Eaton 5-Terminal Ground Bar Kit GBK5CS - The Home Depot

Ground bars are required in all electrical panels, and the aluminum Eaton Cutler-Hammer 5-Terminal Ground Bar Kit is ANSI certified and UL listed for safety. Remember to disconnect the main power in your

www.homedepot.com

I am not an electrician and am a little out of my league. In a GFCI there is a hot, neutral, and ground wire. Somehow GFCI detects currents bleeding out to trip the Circuit. I know enough that opening an AC wire bundle up the black wire is hot, white is neutral, and green is ground. The electricity flows between the black and white, but the green ground wire takes any electrical difference between the devices and equalizes it, like static electricity. Usually its not much like in the instance of walking across a carpet and touching a metal door, but in some instances like a flying helicopter, it builds up enough that touching a rope hanging from it that has not touched the ground can knock you over. I think maybe if the current is bleeding out of the device, it will go to the chassis ground directly instead of through you to the ground.

At least that's what I read about wire colors. However, when I trace them back, it's not always a green wire that goes to the chassis ground in the AC circuit, sometimes it other colors. I really think when the factory assembles these things, they may use the wire that has the most length left on a roll and that would be more important than a green wire going to the ground frame.

 

[Leo3]

At least that's what I read about wire colors. However, when I trace them back, it's not always a green wire that goes to the chassis ground in the AC circuit, sometimes it other colors. I really think when the factory assembles these things, they may use the wire that has the most length left on a roll and that would be more important than a green wire going to the ground frame.

I think you're right.

 

[Leo3]

So if you look at the diagram of the trailer in an earlier post, this neg bus bar is behind the dist panel, not close to batteries. Not nearly as close as the pos bus bar. Is that normal? I will try to trace that black wire. When I was studying the wires up front I did not see any black wire that went toward the rear. Thank you!!

@HRTKD could the chassis be what is connecting the circuit for the negative wire? The neg from one battery goes to the inverter without passing through anything else. The negative from the other battery screws to the trailer frame. Would the trailer frame electrocute you if this were the case?

 

[Leo3]

The bus bar with the many white wires and green screws is your negative bus bar. The big black wire on the right should be the lead coming from the battery. If you connect that lead to your shunt and then the shunt to the bus bar you'll be able to measure your state of charge

If this is right, then that means I could install the battery monitor right there too right? It's supposed to be connected to positive to make the monitor itself power on, and most posts it seems has it connecting to a battery terminal, but maybe any positive will do behind the distribution panel? Actually will connected his to a solar charge controller in this video.

This guy says he thinks it should stay connected to battery all the time and that makes some sense to me. That means it has to be between the battery and the disconnect right?

 

[HRTKD]

The battery monitor needs to be connected as far upstream as possible. As close to the battery as possible. That way it's measuring the battery - and all loads - and not being affected by a voltage drop far down the line.

It's not unusual to see an inverter connected directly to the battery. This is done to minimize voltage drop. In your case, there should be a single lead coming off the battery, to the shunt. Then you can distribute from the load side of the shunt.

The chance of getting shocked is no more with the lead going to the chassis. This is fairly normal. My trailer went to the chassis before it went to anything else.

 

[John Frum]

The battery monitor needs to be connected as far upstream as possible. As close to the battery as possible.

Are you sure?
I think as long as its before the fan out its fine.

 

[HRTKD]

Are you sure?
I think as long as its before the fan out its fine.

It depends. In his case, I suspect that he's going to need a large gauge wire (bigger than is being used now) between the battery and the shunt. I say this because it sounds like they used two leads off the battery bank, one for the inverter and one for everything else. By keeping the shunt close to the battery that should minimize the length of that larger gauge of wire.

 

[John Frum]

It depends. In his case, I suspect that he's going to need a large gauge wire (bigger than is being used now) between the battery and the shunt. I say this because it sounds like they used two leads off the battery bank, one for the inverter and one for everything else. By keeping the shunt close to the battery that should minimize the length of that larger gauge of wire.

I see fan out is at the negative terminal.

 

[HRTKD]

I see fan out is at the negative terminal.

It sounds there are two leads coming off the battery.

The neg from one battery goes to the inverter without passing through anything else. The negative from the other battery screws to the trailer frame.

 

[John Frum]

It sounds there are two leads coming off the battery.

Sounds like a crappie post install modification.