Airstream Basecamp LiFePO4 Conversion System Feedback

amm

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1. If you use the temperature sensor that comes with the Multiplus on the Cerbo GX you can use the Cerbo GX to control a fan. That allows you to skip adding a separate thermostat.
2. Assuming the worst case scenario that you pull a full 150 amps out of the BMS @ 12 volts (that voltage is bit low, but we tend to use that as it's worst case) and have a round trip distance of 8' (4' one way x 2) then 4 awg is the smallest wire you should run. It gives you just under a 3% voltage drop. But like Chris said above, bigger is better. I'm using 2/0 for a 120 amp BMS.
3. The Multiplus 12/3000 has two posts for each DC leg. That means you can run two 2/0 positive cables and two 2/0 negative cables. That gives you a very safe set of cables.
4. The 300 amp bus bar between the BMS and the shunt isn't necessary or is simply in the wrong position. The bus bar should be located downstream of the shunt. You can easily double up 2/0 lugs on the shunt. That's how I did my initial install. In the picture below, I put copper flat bar on the input side of the shunt to give my cables a better mounting surface.
View attachment 101700
5. Similarly, your positive bus bar should be downstream of the switch and fuse. Battery->BMS->Fuse->Switch->Bus Bar.
6. All connections are then made on the common bus bars. Inverter, solar charge controller, Trailer DC distribution panel, Cerbo GX, etc.
7. Your solar charge controller and the Multiplus will both have separate ground (not negative) connections. I put in a separate ground bus bar that those tie into and then there is a cable that goes from the ground bus bar to the chassis/frame.
8. You also need to decide what you're going to do with the 12 volt charge coming in from the 7-pin cable.
1. Thanks, I was wondering about that.
2. Sounds like I will just go 2/0 on everything from the batteries. The one question I have is that between the negative terminal and the BMS. It looks like you used 3x4awg?? Current connected sells the 2x6AWG kit for the BMS I found a formula on another post and it looks like that would support the 198A value I got for 2400W (divided by 2 for 2p) at 10V (low voltage disconnect). 2x4AWG should give me ~250A which should be more than sufficient for that portion?



3. Sounds good. So I will run 2 x 2/0 from bus bars to the inverter just to be safe.
4. Good idea. looks simple enough.
5. Thanks, will change that.
6. Makes sense
7. I have a separate ground bus bar in the trailer already. I will likely need to evaluate the size of that (and cabling size). Assuming this is similar to what I need for the bus bars on the DC side of the circuit. Will plan for 2/0 cabling and 300A bus bar. What did you do?
8. Planning on using the victron DC-DC converter 12/12-18 I think. I don't think the 7pin wiring in my truck can handle much more than that. What did you use?

Thanks again.
 
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HRTKD

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On my BMS I chose the 3 x 8 gauge cable option. That was the largest I could get for the 120 amp BMS at the time.

On my trailer I do not have any charge from the tow vehicle coming into my LiFePO4 battery bank. I simply don't need it. But if I did, the DC-DC charger you listed is the one I would go with. Keep in mind that the 18 amp rating is the output while the input can be higher than that, maybe as much as 30 amps which is real close to the limit of what any tow vehicle will provide through the OEM 7-pin connection.
 

amm

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@HRTKD I am looking at settings for my Multiplus here is what I am thinking....

Low Voltage Cutoff: 12V (~10% SOC)
Float: 13.4V
Absorption: 14.2V
Charge Current 120A

I think these are pretty standard... is this similar to how you configured? Any gotchas?
 

HRTKD

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@HRTKD I am looking at settings for my Multiplus here is what I am thinking....

Low Voltage Cutoff: 12V (~10% SOC)
Float: 13.4V
Absorption: 14.2V
Charge Current 120A

I think these are pretty standard... is this similar to how you configured? Any gotchas?

I think those are close to mine. However, I'm rarely on shore power, so if I've tweaked my charge rates it's to get the batteries charged faster than my solar charge controller would.
 

amm

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Thanks for the feedback everyone. Just completed the battery install. still waiting on more time away from work to do the inverter side of things.... I am having trouble getting my F150 to detect the trailer and trigger the alternator with the DC/DC charger installed. I don't really care about charging from the TV but more not discharging my batteries back into the TV. My current configuration I have is the positive and negative from the 7-pin into trailer wired to the orion and then that pushing to my battery. I can't reliably get the F150 to kick on the 7pin. Is there something I am missing? Should I just wire this and make is non-isolated? or just wire a dummy battery in so that the F150 engages the trailer?
 

HRTKD

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Thanks for the feedback everyone. Just completed the battery install. still waiting on more time away from work to do the inverter side of things.... I am having trouble getting my F150 to detect the trailer and trigger the alternator with the DC/DC charger installed. I don't really care about charging from the TV but more not discharging my batteries back into the TV. My current configuration I have is the positive and negative from the 7-pin into trailer wired to the orion and then that pushing to my battery. I can't reliably get the F150 to kick on the 7pin. Is there something I am missing? Should I just wire this and make is non-isolated? or just wire a dummy battery in so that the F150 engages the trailer?

Can you clarify the "reliably" part? Ford, in their infinite wisdom and desire to protect us from ourselves, has a rather complicated trailer charging system that requires you to have certain checkpoints complete before the truck will send any current. If you're trying to test the charge to the trailer while the truck is stationary you have to be very cognizant of these checkpoints. On my 2017 F-350, the engine has to be running and I have to have pressed the brake pedal after the engine was running. Other model years seem to have different checkpoints. Here is a YouTube video of a guy going through the entire process of figuring out what all the checkpoints are on a F-series truck that you might find useful.

 

amm

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Can you clarify the "reliably" part? Ford, in their infinite wisdom and desire to protect us from ourselves, has a rather complicated trailer charging system that requires you to have certain checkpoints complete before the truck will send any current. If you're trying to test the charge to the trailer while the truck is stationary you have to be very cognizant of these checkpoints. On my 2017 F-350, the engine has to be running and I have to have pressed the brake pedal after the engine was running. Other model years seem to have different checkpoints. Here is a YouTube video of a guy going through the entire process of figuring out what all the checkpoints are on a F-series truck that you might find useful.

Thanks, by reliably I mean that I got it to work once and never again (no 12V coming from vehicle. I will retry the different iterations in the video as part of the debug. . Also, I am wiring both the positive (black) and negative (white) from the 7pin into the orion and putting the output of the orion to their respective bus bars. It looks like the trailer lights are very dimly lit in that scenario, I am assuming this is because the truck isn't providing the correct voltage due to lack of detection coming from the 7pin?
 

HRTKD

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Going back in the posts, it looks like you have a 20 amp DC-DC charger. If your batteries are at a low state of charge, such that they can consume a large amount of amps, your DC-DC charger could very well try to pull more than 25 amps on it's input side from the tow vehicle. The very most you'll get from the 7-pin circuit is 30 amps and even that is optimistic. The actual amount of current is likely to be lower than that.

It's possible that your charger is overwhelming the circuit or may have blown a fuse. But it's also possible that your truck hasn't engaged the charge circuit. Try some of the checkpoints from that video to see if you get any results.
 
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