Disconnecting 12v charge current from tow vehicle?

[Ksears]

Hey all,

2010 27FB, 2015 Ram 1500 here.

I just installed some pretty expensive lithium batteries, and I'm trying to determine if I can disconnect the 12v power coming from my 2015 Ram 1500. My assumption is that one of the other pins on the 7 pin connector is supplying power to the breaks, but I figured this would be the best place to ask.

[55AS]

Here you go.

[Al and Missy]

You may be able to just pull a fuse on your Ram. Check the manual for a fuse for trailer 12V or trailer charge, or something like that. After pulling the fuse, check to make sure your brakes still work. My F-150 had a fuse just for the charge line.

Another alternative is to find the charge line at your 27's DC panel and disconnect it.

Al

[ghaynes755]

Pull the fuse. Or install something like the Victron Cyrix-ct 12/24V-120 battery cmb. Good diagram at https://amsolar.com/rv-battery-accessories/98-altagmtow as you build your system.

[wulfraat]

^^^^

Yup pull the trailer aux fuse in your fuse box. My 2500 gmc had a 30A fuse dedicated to the aux charging line on the 7-way. I pulled to so as not to mix and match voltages across lead acid and lithium. Works like a charm and takes 15 seconds once you know which one. Just check your book.

If you go the victron route you need an Orion DC-DC converter. Just search “Orion” on the forum and you’ll pull up posts and I shared model number in the past....

[ghaynes755]

Missed the lithium bit. Here's the AMSolar setup for use with LiOn batteries. Does not require an Orion unit.


https://amsolar.com/rv-battery-accessories/98-altclitow

[Ksears]

You guys rock, thank you! I found the positive charge line where it tied into the positive bus bar under the bed. I disconnected that and we're in business .

[Ksears]

Originally Posted by ghaynes755

Missed the lithium bit. Here's the AMSolar setup for use with LiOn batteries. Does not require an Orion unit.


https://amsolar.com/rv-battery-accessories/98-altclitow

So I looked into this a little bit ago, and I had interpreted the install as needing to run a new positive and negative line straight from the battery-- is that not the case? Don't the existing lines connect directly to the vehicles alternator?

[Ksears]

I just checked out AM Solar's diagram, and it looks like they're using Battleborn drop-in replacements. Those batteries have an internal BMS that regulates voltage going into the cells, enabling them to take current straight from the alternator, whereas I have raw LiFePo4 cells with no BMS, so I would need something like the Cyrix to regulate voltage. (I think)

[waninae39]

get a battery isolator between the TV and AS.

we use a victron converter/inverter to chnarge our lion from AC/solar. we tell it we have BB lion battery and program the correct parameters as given by BB.

it works like a charm

[uncle_bob]

Hi

If you are running a lithium setup that does *not* have a BMS ... yikes ..... that's not a good idea at all.

Even with a BMS, you need to do something about the alternator. It's set up to charge a lead acid chassis battery. Dropping a lithium across a lead acid (which is what the charge line is doing) means that one or the other is not getting what it should. Either you nuke the lithium or the lead acid.

Best bet is to spend $80 on a DC/DC converter. Set it at 13.4V and forget about it.

Bob

[TheGreatleys]

Originally Posted by uncle_bob

If you are running a lithium setup that does *not* have a BMS ... yikes ..... that's not a good idea at all.

!! [emoji2957]

RIP your very expensive batteries...

[Wazbro]

I would NEVER do a long term fix on the TV, any long term fix should be on the trailer side.

What happens if you break down and need to have someone else tow your trailer?

Destroyed batteries, maybe even with telling them it's needed.

[wulfraat]

Originally Posted by Ksears

I just checked out AM Solar's diagram, and it looks like they're using Battleborn drop-in replacements. Those batteries have an internal BMS that regulates voltage going into the cells, enabling them to take current straight from the alternator, whereas I have raw LiFePo4 cells with no BMS, so I would need something like the Cyrix to regulate voltage. (I think)

You need a victron Orion dc-dc converter to regulate voltage per post #5....