Factory installed DC to DC charger

[SeaDawg]

We I installed the little orion in the boat this week. It's a great little piece of equipment. 

[Ronbrink]

On 2/10/2025 at 9:30 PM, jd1923 said:

Either way, mounting under the bumper was the mistake made. Besides the greater chance for damage, it makes it hard to reach. I'm thinking the cables and SB175 will come out somewhere between the bumper and license plate.

Recently completed the cable transfer from my former TV to the Savana van for the DC-DC setup. On the former, the 7-pin outlet was well protected on the bumper next to the license plate and at the recess designed for a ball hitch mount, the receiver hitch being below the bumper. The van however, came stock with the trailer cable connections affixed to the receiver hitch cross beam, underneath the bumper. That being, I mounted the DC-DC Anderson connection likewise. My hope is the rather robust receiver hitch cross beam will serve as a skid plate and protect said connections! 

[Ronbrink]

On 2/10/2025 at 9:30 PM, jd1923 said:

For the DC-DC charger, I'm not going to pop the hood and throw a switch every time we hitch and unhitch. Much too much bother.

You may recall, I installed a solenoid to activate power to the DC-DC cables leading to my rear bumper-mounted Anderson when the motor is running and thus, no power when off. That said, I also do not want these cables powered while running and not trailering, unless the Anderson is needed for others purposes like the VIAIR or an alternative Dometic fridge/freezer power source. Therefore, I installed a toggle switch for the solenoid trigger wire, which leads into the van interior for convenient toggle activation, as needed. 

Edited February 16 by Ronbrink

[Ronbrink]

On 2/10/2025 at 9:30 PM, jd1923 said:

Admin, please remove this, I inadvertently made a duplicate post. Thanks

Edited February 16 by Ronbrink

[jd1923]

1 hour ago, Ronbrink said:

You may recall, I installed a solenoid to activate power to the DC-DC cables leading to my rear bumper-mounted Anderson when the motor is running and thus, no power when off.

Agreed Ron, you have automated this with an ignition circuit solenoid and if I though it was more important, your design is the way I would go too. I was referring to others who have mounted a manual switch under the hood.

[Ronbrink]

43 minutes ago, jd1923 said:

Agreed Ron, you have automated this with an ignition circuit solenoid and if I though it was more important, your design is the way I would go too. I was referring to others who have mounted a manual switch under the hood.

Understood, I was simply reinforcing your thoughts about having an on/off switch under hood and sharing an alternative to others on the matter. Originally, I installed a circuit breaker fuse with manual reset to serve as an on/off switch as well, but added engine temps during extreme heat conditions would cause it to trip. No bueno! I replaced it with an ANL fuse holder/60A fuse for cable protection and the toggle switch for manual on/off capability; again, information for those that may not be in the know. 

Edited February 16 by Ronbrink

[Geronimo John]

3 hours ago, Ronbrink said:

Recently completed the cable transfer from my former TV to the Savana van for the DC-DC setup. On the former, the 7-pin outlet was well protected on the bumper next to the license plate and at the recess designed for a ball hitch mount, the receiver hitch being below the bumper. The van however, came stock with the trailer cable connections affixed to the receiver hitch cross beam, underneath the bumper. That being, I mounted the DC-DC Anderson connection likewise. My hope is the rather robust receiver hitch cross beam will serve as a skid plate and protect said connections! 

Your logic line is the same I used.  I also figured that there was no way that the ground would ever get in the way of my Anderson that I had mounted below and in front of the rear bumper on our F-150.  But alas a young driver on a very tight mountain switchback trail road proved me wrong.  He unknowingly backed my TV into the sloped side of the mountain and crushed my TV Anderson plug.  No electrical problems as I always turn off power at the battery circuit breaker when not towing. 

Experienced as your are, I know that you'll be wise when backing back up to bumper blocks and curbs.

GJ

[jd1923]

Yay, wired our Oliver for the DC-DC charger today!
(TT side only, wire lengths installed hitch to buses, no connections made yet)

An injury and then rebuilding the waste valves took precedence. But after Reading @Ronbrink's comment (thanks Ron) about running the wires around the toilet and not having to remove the vanity shelf, I thought since I have the waste valves removed under the front dinette seat, I should get this done before putting them back in.

I pulled the two valves yesterday and then thought, a couple of hose clamps and I could pull it all out and inspect for condition inside and clean the area. Good thing I rinsed the toilet 4 times when we dumped tanks. The 4 AWG wire is now laying across the floor in the picture.

It made the wiring soooo easy! I stuck my head down where the waste valves were installed and looking forward I could see the OEM installed cables coming through the hull. I'll see if I can take a picture of it.

If they truly sold me 65 ft and I have 28 left, then I used 37 ft for the round-trip in the Oliver (2 x 18.5 ft). I ran it as straight as can be leaving some extra length where the buses are located under rear dinette seat, and outside I made it 5" longer than the trailer cable to be safe. The amount left over is enough for the + run to the starter battery (~20 ft) with 8' left over for rear and front frame grounds, and a 4 AWG straight run from battery to alternator.

We're leaving to Catalina State Park and the Coronado NF a week from Monday, so completing the DC-DC charger installation is second to getting the waste valves finished. So glad, I got this wiring run today. I'll be happier when the plumbing is done!

Edited February 17 by jd1923

[jd1923]

On 1/1/2025 at 4:52 PM, Snackchaser said:

The lengths are total for both the positive and negative wires:

• #4 up to 30’ (23’)
• #2 up to 48’ (37’)
• #1 up to 60’ (46’)
• #1/0 up to 76’ (58’)
• #2/0 up to 96’ (74’)

WOW!  As you can see, your modified 65’ length calls for size 1/0 wire, and that’s without adding the frame resistance.  It’s 2/0 for my 90’ length.   The cable size calculations are to safeguard from overheating the wire and to avoid unacceptable voltage drops, the same reason why Oliver disconnects the #10 TV charging circuit for amp hungry lithium systems.  But as you pointed out, the charger output can be derated 😂

I understand the EE standard calculations. Question though... How am I charging at 50A through a 25 ft 10 AWG cable in series to a 14 AWG extension cord? (see pictures)

We left home yesterday batteries down to 34% after running our fridge for 48 hours on DC, lights and radio, etc. We usually leave with full batteries and tanks but day one was only 2 1/2 hours to Lost Dutchman SP were we could charge and fill the FWT.

When we got here we had a drive-through site and want to park the opposite direction, so I needed the extension cord. First I turned the MP2 to inverter only (no charging) and ran the HWH on AC. Even though we were connected, I guess the MP2 sensed not enough available amps on the 20A shore power connection and was pulling 127A DC from the batteries. This translates to approx. 10A 120VAC but maybe the HWH was using 10A in addition to the limited shore power. I should have checked the EMS readout for shore power amps used but did not think to at the time.

A half hour+ later we had hot water, we turned the breaker OFF, and the 600AH batteries were now at 20%. The Victron picture taken at 11 PM (5 1/2 hours later) showed the batteries up to 60%. This adds up that the charger was supplying 50AH. When I woke up in the middle of the night the batteries were at 100%. The extension cord never got hot.

What's the deal here? Does the 14 AWG cable work because voltage is 120VAC and the 4 AWG will not be enough for 50A at 12VDC (13.6V actual)? Also, does voltage drop really matter when the Orion XS 50A accepts input voltage as low as 9V? (input range spec 9V - 17V)

[Snackchaser]

JD, I was reading your post, but I struggle with acronyms.  I believe you’re asking why a 120-volt current through a #14 gauge wire can charge at 50 amps, while a 12-volt current through a much larger #4 gauge wire can’t.

The answer lies in Ohm’s Law (E=IR), which states that voltage (E), current (I), and resistance (R) are directly proportional.  Therefore, as voltage increases, current decreases.  A good analogy is the 700 kilovolt transmission lines that can power a city through a wire the size of your thumb. If you reduce the voltage to 120 volts, then you would need a wire thicker than a redwood tree to carry all the amps.

Regarding the Orion, it’s a type of Buck Booster, which means it can increase the voltage of a low-voltage input to a higher voltage output.  However, an undersized feed cable from the tow vehicle still experiences voltage drop due to cable resistance (E=IR again), which will affect the charger’s performance.

Look at it like a toaster, the heating element is basically an undersized conductor that is heating up due to its high resistance.  It effectively limits current exactly like a resistor in an electronic circuit does.

I hope that answers your question, and I apologize if I’ve misread it.

Cheers!  Geoff

[jd1923]

10 hours ago, Snackchaser said:

JD, I was reading your post, but I struggle with acronyms.

Sorry about that, I generally do not use so many. I’m sure you know the electrical acronyms like AWG, VAC and VDC.

I also used FWT for fresh water tank and HWH for hot water heater. MP2 is short for the Victron Multiplus II Inverter/Charger.

I got the 4 AWG wires run in the Oliver last week while working on waste valves. We’re camping this week but I will get this done in another week or two. I will run tests setting the Orion XS 50A configured at 30, 40 and 50 amp settings. 30A will be no problem and we’ll see if it can run somewhat higher without issue.

You did answer my question, thank you. I answered it myself at the end of my post and you confirmed my thinking.