Travel trailer - 24v battery - buck converter question

[Jusbechillin]

RV Solar Power Blue Prints

Building a vehicle mounted solar power system? Let me help.

www.mobile-solarpower.com

Following system design advice From this website, I bought a 40a 24v>12v buck converter to go with my 280ah 24v LIFEPO4 battery bank.

The legacy distribution panel in the RV (see pic attached) has 150 amps of branch circuits on the dc side.

How does the buck converter I bought wire into the system Downstream AND isn't it undersized being rated at 40amps considering the rv panel is rated at 65 amps?

 

[Master Dalor]

Hello. if you pull 15 amp from each branch, it will not deliver enough. you must stay reasonable, and pull not more than 40 amps in total, you could put an automatic fuse, smaller or equal to 40Amp,
if the dc to dc is short circuit protected, (cc cv) no arm can be done.
It must connect on the left side, instead of the red for positive, the back for negative. If the old wire came from the car battery, it must be isolated.
Between the solar panels and the battery, you must use a charge controller.

 

[Master Dalor]

If your solar array can give 65Amps you must choose a charge controller witch accepts that.
You must also known how much volt is given by your pv. if you mutiply the 65Amp by the volts, you get the power in watts.

 

[John Frum]

How does the buck converter I bought wire into the system Downstream AND isn't it undersized being rated at 40amps considering the rv panel is rated at 65 amps?

Yes its undersized.
The converter manual is here https://wfcoelectronics.com/wp-content/uploads/2019/06/8900MBA-Series-Manual.pdf
Page 5 shows how to wire it.

buck_converter.pos->panel.vcc
buck_converter.neg<-panel.neg

Looks like neg is common and it looks like there is a battery connected, confirm?
Is that battery also connected to the breakaway system?
What else is connected to that battery?

 

[Jusbechillin]

Looks like neg is common and it looks like there is a battery connected, confirm?
Yes with 6awg wire. Two 75ah 12v deep cell batteries wired in parallel.

Is that battery also connected to the breakaway system?
Yes.
What else is connected to that battery?
Battery positive connects to busbar with a few items connected (see photo). I will have to do research to see where all of them go. One goes to the breakaway for sure and has a 15a fuse. I assume the others run the trailer lights and brakes. And I believe the powered hitch and powered leveling legs run from this as well. I will respond later tonight with the exacts.

 

[Heap64]

I'm looking at this for my travel trailer.

Victron Energy ORI241270020 Orion 24/12-70A DC-DC converter

 

[John Frum]

Looks like that battery runs the breakaway system in addition to the dc panel.

From the research I've done that buck converter only puts out 12.2 volts and therefore won't even come close to charging that battery.
I suggest you try powering the converter via the inverter.

 

[John Frum]

I'm looking at this for my travel trailer.

Victron Energy ORI241270020 Orion 24/12-70A DC-DC converter

Anyone know if 13.2 volts enough to keep that lead acid battery healthy?

 

[schmism]

this was recently debated in a different thread. Typically a small 12v battery is housed on the tongue of the trailer for the breakaway and is charged by the 7way connector from the tow vehicle. The consensus was to keep this in place and keep it separate from the rest of the 12v on the camper.

 

[Jusbechillin]

Battery connections.

• Power tongue jack
• Breakaway brake system
• Automatic leveling system
• Battery disconnect switch
  

There is one purple wire connected that disappears up into the RV that I cannot trace. It appears to be approx 12awg

 

[John Frum]

this was recently debated in a different thread. Typically a small 12v battery is housed on the tongue of the trailer for the breakaway and is charged by the 7way connector from the tow vehicle. The consensus was to keep this in place and keep it separate from the rest of the 12v on the camper.

Thing is @Jusbechillin has a 24 volt system.
I want nothing to do with the breakaway system but the breakaway battery needs to be healthy and I suspect the 7 pin won't keep it that way.

 

[John Frum]

There is one purple wire connected that disappears up into the RV that I cannot trace. It appears to be approx 12awg

Mystery wires, great.

 

[Jusbechillin]

I suggest you try powering the converter via the inverter.

Don’t connect the dc into the legacy panel from the new battery bank?

Let the ac output from the inverter/charger feed the entire legacy panel?

 

[John Frum]

Battery connections.

• Power tongue jack
• Breakaway brake system
• Automatic leveling system
• Battery disconnect switch

There is one purple wire connected that disappears up into the RV that I cannot trace. It appears to be approx 12awg

If you want to isolate that battery from the dc panel and let the umbilical cord take care of it, its fine by me.

 

[Jusbechillin]

Would hooking up the victron dc-dc step converter to the existing positive connections terminated here do the trick for the items that are currently wired here?

 

[Master Dalor]

Hello.
Do you intend to keep those deep cycle baterries or to replace them with the 24V 280Ah lifepo4 battery bank?
Is your 24V 12V dc to dc converter meant to power the loads or to charge another battery?

It seems that in the actual configuration the legacy distribution panel is directly powered by the deep cycle 24V battery, and you don't have 12V.

In that case, the 24V 12V dc to dc converter would need to be powered by the 24V battery via a 25Amp fuse, and the 12V output will need a 40Amp fuse, and smaller fuses for each 12V load you will apply to it.

 

[Master Dalor]

Looks like that battery runs the breakaway system in addition to the dc panel.

From the research I've done that buck converter only puts out 12.2 volts and therefore won't even come close to charging that battery.
I suggest you try powering the converter via the inverter.
[/QUO
hello joey. Here on the link you provided it seems to give 14,4V

 

[John Frum]

@Master Dalor
Its the 24 to 12 buck converter we are talking about https://www.amazon.com/dp/B01LYK6G2Y

 

[Master Dalor]

Ah ok. Thanks, sorry, I must have missed posts, you know I'm a newbie in the forum.

 

[Jusbechillin]

Sorry for not responding, smoothJoey is helping me out. Thanks!