Direct Charge Circuit

[Kountryguy]

I would like to run a direct line from my truck alternator to the house batteries in my fifth wheel trailer. Has anyone done this project that could offer some suggestions on how to and what materials used? Any help will be appreciated.

[time2roll]

Gjac wrote:
My MH is winterized now and 1200 mis away. But if I remember correctly after a week of dry camping my chassis batteries were depleted about 30% and the 2 6v house batteries were 50%. Voltage at house batteries were 14.1 v and house were at 13.7 or 13.8 v. On a 5 hr drive home at 60 mph I was reading about 5.5 amps going into the house batteries. Would a voltage drop of .3 v cause this?

Normal at the end of the drive. Initially the amps should have been higher. 6 amps would not be enough to immediately increase voltage from 12.4 to 13.8. But you are only down 30% so the charge will slow as you get above 80%. RJ is talking initial amps when the battery is way low. And if I know RJ he says 50% but they are probably even a little more discharged.

Another good reason to have 200+ watts of solar going direct on the house battery.

[pnichols]

Sal's suggestion for situations where there's a long wire run between the alternator and the batteries to be charged is indeed the best way to do it.

Otherwise, as others have said, the largest practical wire size should be used between the engine battery or alternator and the RV batteries for direct connection together of all of them.

However just for information purposes, perhaps our Ford alternator setup is a bit different: When our RV batteries are way down, the alternator will provide 20-30 amps into the RV batteries over 6-8 feet of 6 gauge cables for several hours while driving. It may be that the 200 amp hours of discharged RV batteries reduces the overall voltage of the three batteries in parallel enough such that the alternator merely is sensing that a "large engine battery" is heavily discharged and hence needs this level of charging current.

[Salvo]

You're just not going to get large currents from the alternator. Current may peak at 60A for a second or so, but will quickly taper.

A better alternative is to install an inverter in the engine compartment. Run a 120V ac cable to a small converter (like a 30A Iota IQ4) that's located next to the battery. This is guaranteed to work a lot better.

Sal

[Gjac]

smkettner wrote:

Gjac wrote:

RJsfishin wrote:
Those trailer owners that think a full charged chassis battery won't let other paralleled batteries charge, are invited to look at my MH w/ an ammeter shunted right at the alternator. Yeah, that's what I have, and you'll see I constantly get a 60 amp charge to 50% discharged house batts, w/ a full charged chassis battery.

Rich can you describe how you achieved this rate of charging? I only see 5-6 amps of charge from a 180 amp alternator and 2 6 v batteries at 50% SOC.

Easy. Measure the voltage at the alternator. Then measure at the 50% low GC2 batteries. Post the measurements.

Then trace along the path to find the voltage drop. Improve those areas until the amps start moving. You should aim for 0.2 to 0.4 voltage drop max between the alternator and house battery. The lower the voltage drop the better.

My MH is winterized now and 1200 mis away. But if I remember correctly after a week of dry camping my chassis batteries were depleted about 30% and the 2 6v house batteries were 50%. Voltage at house batteries were 14.1 v and house were at 13.7 or 13.8 v. On a 5 hr drive home at 60 mph I was reading about 5.5 amps going into the house batteries. Would a voltage drop of .3 v cause this?

[pnichols]

Just as a reference point:

Our motorhome came with 6 gauge cabling built-in between it's Ford alternator and the two coach batteries. Of course, the engine battery is also connected to the alternator - so we have three 12V batteries all in parallel with each other getting charged by the Ford 130 amp alternator when going down the road.

I have a coach battery digital ammeter mounted right on the dash and I've seen the alternator dump up to 50 amps through the 6 gauge cabling into the coach batteries when the coach batteries were discharged but with the engine battery fully charged. Of course our 6 gauge cabling is probably only 6-8 feet long going from the alternator to the coach batteries.

[64thunderbolt]

Leece-neville made an alt in the old days for semi's It had a square plug on it. Pull in out, turn 90* plug back in Do this in all 4 positions and everyone had a different output. Fron 60x to 110a. Not sure if they are still around but with some fab skills one could add this and have a dedicated charging systwm for the trailer. The Ford 7.3 & 6.0's have an anbulance pkg for 2 alt one for the vehicle and one for the coach. My tuuck came with the mount So I could add the other alt and just wire it to the trailer not not worth the expense or work IMO. I have survived 15 yrs without it but would be a nice setup.

[jhilley]

Another good choice for connectors are Anderson Power Poles

Anderson Power Poles

[msiminoff]

Kountryguy wrote:
Has anyone done this project that could offer some suggestions on how to and what materials used? Any help will be appreciated.

I did exactly what you are describing; I ran a 2 gauge power and ground charge leads from my (180A) alternator/starting battery to the battery bank in my truck camper. I have seen charge current in excess of 100A @ 14.7V when the camper battery is deeply discharged. I installed a "lift-gate connector" in the truck bed to make the connection between my truck & camper. Of course there are fuses at both the truck and TC ends of the positive lead. In addition I have a volt/ammeter (w/shunt) in the truck cab to monitor charge voltage & current.
Note that I chose to use a high-current manual disconnect switch rather than a solenoid.
Photos below…

After seeing what I'd done, my father subsequently installed an identical setup between his Dodge Ram truck and Airstream TT…. I see no reason why the same couldn't be done with a 5th Wheel.

Cheers
-Mark

[time2roll]

Gjac wrote:

RJsfishin wrote:
Those trailer owners that think a full charged chassis battery won't let other paralleled batteries charge, are invited to look at my MH w/ an ammeter shunted right at the alternator. Yeah, that's what I have, and you'll see I constantly get a 60 amp charge to 50% discharged house batts, w/ a full charged chassis battery.

Rich can you describe how you achieved this rate of charging? I only see 5-6 amps of charge from a 180 amp alternator and 2 6 v batteries at 50% SOC.

Easy. Measure the voltage at the alternator. Then measure at the 50% low GC2 batteries. Post the measurements.

Then trace along the path to find the voltage drop. Improve those areas until the amps start moving. You should aim for 0.2 to 0.4 voltage drop max between the alternator and house battery. The lower the voltage drop the better.

[Gjac]

RJsfishin wrote:
Those trailer owners that think a full charged chassis battery won't let other paralleled batteries charge, are invited to look at my MH w/ an ammeter shunted right at the alternator. Yeah, that's what I have, and you'll see I constantly get a 60 amp charge to 50% discharged house batts, w/ a full charged chassis battery.

Rich can you describe how you achieved this rate of charging? I only see 5-6 amps of charge from a 180 amp alternator and 2 6 v batteries at 50% SOC.

[jhilley]

I would put in a regular Battery Isolation solenoid rated at at least 80 amps with the coil connected to ground and the ignition switch. The Bosch type relays are only good for about 30 amps. You dould also use a dual battery diode isolator, but the solenoid will give you a higher charging voltage.

[RJsfishin]

Those trailer owners that think a full charged chassis battery won't let other paralleled batteries charge, are invited to look at my MH w/ an ammeter shunted right at the alternator. Yeah, that's what I have, and you'll see I constantly get a 60 amp charge to 50% discharged house batts, w/ a full charged chassis battery.

[time2roll]

Here are some posts in the Truck Camper forum:

Camper_Jeff_&_Kelli wrote:

Matthew_B wrote:
I'd like to make a request to have a separate TCU sticky thread on upgraded charging systems. I've posted about my system in my camper mod page, and there are a couple of other threads floating around about doing the same thing. This topic comes up often enough that it seem like a good idea to have a tread with one stop info on people's various systems.

I'll start with a repost of my setup, and I invite those in the 6 gauge, 4 gauge or 2 gauge club to join in.

I listed a few choice threads that were pertinent at the time I was doing my upgrade project research.
Links are halfway down the page and as the post goes on, there are references to other threads as th...

Here are a couple links to other threads that have been of great help doing this project.

Matthew_B, Alternator Charge Cable Installation to TC.

BC Sierra, Alternator Charge Cable Installation to TC.

JoeChiOhki, Power Converter Thread.

Battery Discussion Thread

Battery Warmer Thread by Sleepy

My earlier discussion thread.

My original post relating to installing large 4 gauge wire.

This is the first thread with a report on charge cable performance.
J

Original thread - go to end

Although I suggest going with 200w to 500w of solar on the trailer roof. Solar works when camped and while in transit as long as there is sun.

[beemerphile1]

You can run larger wire and still utilize the Bargman connector. Just replace the existing wire. Don't forget that the ground wire needs to be upgraded as well. The ground must be as large or larger because it is also being used by the lights and brakes.