Sanity check before I run new wire

[ripperj]

I have a 21 Ram 3500 crew cab long bed with a Truck camper. Dual alternators(360 amp)

I installed a new 200ah LiFepo4 12 volt battery in the truck camper. The charger is right next to the battery.

I have a new 30 amp Victron Orion 30amp dc to dc charger.
The charger is running off the the 7pin trailer plug which is all 10awg. Probably 25’ one way

The charger keeps tripping off as the input voltage drops to 8ish volts. (Even with truck running)
If I set the charger drop out voltage to 8.0 it usually will charge, but this doesn’t seem right.


I can run #6 from the battery to the charger, and probably lose about 12’ of wire)but all the voltage drop calculations don’t show this big of a drop(what I’m seeing with the #10), but I’m sure the trailer 7pin plug contributes a lot of loss.

Do you think #6 is the answer?
Thank you
Keith


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[Hegear]

Are you calculating the length of the circuit or just the length of you positive cable? If you think it’s 25ft you would have to double that for your voltage drop Calculation. I am not an expert but thought It might help.

 

[ripperj]

The online calculator I used (I tried a couple) account for the second cable.
Both showed about 1.7 volt drop at 30 amps.
The couple times the charger was working I only saw 16 amps

Thank you for the reply


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[Dave in AZ]

The online calculator I used (I tried a couple) account for the second cable.
Both showed about 1.7 volt drop at 30 amps.
The couple times the charger was working I only saw 16 amps

Thank you for the reply


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30A, 10Awg. 3% voltage drop is 10ft circuit length, or 5ft one way.
10% voltage drop is 30ft total, 15ft one way.

The 7 pin is not meant to supply 30A. Run your own positive AND NEGATIVE TOO!

There are probably 100 threads on guys trying, and failing, to power 20A or more on their 7pin. Go here for the best info on running alternator dc dc chargers to power stations in vehicles:

Vehicle Mounted Systems

RV's, Vans, Trucks and More! Typically 12v, and 100-1000w, but the limits are endless!

diysolarforum.com

 

[ripperj]

I ordered 6awg and an Anderson plug as well as a Blue Sea MRBF fuse block.
Hopefully it will cure the issue


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[highwest]

My 7 pin connector puts out about 5A, sometimes less. I’m certainly no expert, but I always keep this Blue Sea chart around when I’m doing 12V projects and try to stay in the 3% voltage drop zone, if possible.



6AWG should get you much better results. Good luck on your install.👍

 

[DiploStrat]

You have the answer, but, to be a wag, I would say that the only insanity would be to use the 7-pin plug!

B2B or DC-DC chargers are about 90% efficient, so a 30A charger needs to be fed with wire big enough to provide 35A within the input voltage tolerances. Bigger is ALWAYS better.

 

[ripperj]

Thank you for all the input.

I knew going in that the 7 pin was not ideal, but I thought I could limit the current on the charger , but that’s not a feature on this Victron.

Highway-that’s a pretty cool chart, makes it pretty simple. Thx


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[ripperj]

Major hassle, my whole under carriage is covered in fluid film, I looked like a coal miner when I got done running the wire along the driver side frame.
Waiting on a MBRF fuse block

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[dstefan]

Major hassle, my whole under carriage is covered in fluid film, I looked like a coal miner when I got done running the wire along the driver side frame.
Waiting on a MBRF fuse block

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Since that looks like its gonna be exposed to the elements a bit (?) you might want to check out a pair of these:

SB50 Environmental Boot with Cover, Source Side

Soft shell boots provide water, dirt, chemical and UV protection to SB connectors. Rated to IP64 when mated or unmated when the integrated cover is used. Customizable cable legs can be trimmed to fit various gauges. Both AWG and mm2 sizes are referenced.

powerwerx.com

I have a pair waiting to be installed and they are very well made.

 

[ripperj]

Thx, I do need to get those. I had them on my winch plugs on my last truck and they worked out great


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[DiploStrat]

So, problem solved?

 

[ripperj]

I won’t know until after work, my Blue Sea terminal fuse block didn’t arrive until after taco night

On a weird note. I assume the input and output negatives are tied in the isolated version of the Orion charger.

The only wire hooked up in my 7 pin plug now is the green wire to the marker lights. The black and white are taped off.
The negative wire on the marker lights is tied to the battery negative buss in the camper which is not connected to the truck.

The hot for the markers comes from the truck. The marker lights still work, so the negative must be tied thru the charger?


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[ripperj]

The charger now works perfectly. 29.9 amps bulk charge.
I’ll do some long term testing, but I think I’m good to go.

Thx for the help


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