Direct Charge Circuit

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.

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.

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

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?

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.

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.

Another good choice for connectors are Anderson Power Poles

Anderson Power Poles

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

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.

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.