More DC to DC charger installation tidbits

Snackchaser · February 20

I just completed installation of a Victron Smart Orion 30 amp isolated DC to DC charger after reading all the great information provided in this forum by MAX Burner, and others. I really appreciated all their groundwork and details, so I wanted to share some of my experiences in the hope that others will find it useful.

I used #4 AWG wire for ease of installation and for better termination options. BatteryCablesUSA recommended their “Jumper Cable” wire and it was the best deal I found at $197 for 55’ x 2. It consists of a black and red cable joined together like zip cord, and it’s flexible enough to lay flat under it’s own weight. Their lugs and heat shrink were also reasonably priced. I sheathed the full length of the cable with 3/4” braided cable sheath for extra protection and good looks (Amazon Keko 100’ roll for $21.) I seized the ends with Amazon XFasten fabric Wire Harness Tape (5 rolls for $14.)

BatteryCablesUSA also recommended Anderson SB50 connectors, instead of the larger #4 AWG rated SB120 connectors that I originally planned. They said that #4 AWG wire would fit in the SB50 #6 AWG contact pins, which it did.

I used Trailer Vision covers for the Anderson SB50 connectors. A TV-201426-50 surface mount receptacle with hinged cover plate was installed under the truck bumper. It has a red LED power indicator that I discourage from connecting because it’s on all the time and annoyingly bright. They also offer a flush panel style mounting.

The sheathed cord on the trailer side got the Trailer Vision TV-328993-50 plug cover. It has a protrusion that catches on the mating receptacle’s hinged cover to stop it from pulling out. It’s similar to how the 7-pin connector ports hold the plug in. It also has a LED power indicator that’s more useful because it’s only on when connected. It uses a compression gland for the cable that I filled with black RTV.

Powerwerx company sells Trailer Vision parts, Anderson connectors, and other accessories for reasonable prices. Get at least 4 extra #6 Anderson pins for connecting to the Victron compression terminals as explained later. Powerwerx also sells the “PanelpodSB,” which is a surface panel mount Anderson SB50 housing for $11.99. I mounted one on the Oliver’s cargo box for “parking” the Anderson connector when it’s not plugged into the truck. It keeps with my existing theme of parking places for the 7-pin cable and RAM rear view camera cable. They also sell a tethered cap to keep it clean when traveling.

The engine compartment wiring was straight forward. I connected the cable’s red wire to a 60 amp terminal post fuse on the battery positive. The black wire terminated to the battery negative.

The trailer half of the sheathed cable went through a penetration behind the LP tanks. A hole was drilled through the trailer wall next to the existing penetrations with a 1-1/8” step bit. The sheathed cable passed though an Amazon PA66 1” nylon cable gland ($7.99 for two.) I used a short piece of heat shrink over the sheathing where it passed through the gland and filled the gaps with black RTV. The shelf under the bathroom sink has to be removed for access to the inside cable penetrations. From there the cable can be simply pushed under the floor to the rear dinette seat where the Victron was mounted.

The Victron has some great safety features that will automatically reduce, or shutdown, the output if it gets too hot or the input voltage drops too low. It’s important to take this into consideration because it would likely happen while driving, and you wouldn’t know it without constant monitoring.

Voltage drop especially comes into play with the new smart alternators that lower voltage output to save energy. The Victron’s default voltage settings account for this. However, due to the longer run of cable needed with travel trailer installations, the cable resistance can cause enough voltage drop where it can go below the default settings and cause the Victron to derate it’s output.

I calculated the voltage drop for different wire gauges at 35 amps (nominal input current) and a cable distance of 53’ x 2. The results don’t include the connector and termination losses:

1.46 volt drop for #6 AWG

0.92 volt drop for #4 AWG

0.58 volt drop for #2 AWG

Per Victron’s instructions, a 0.6 voltage drop can cause a “Voltage Lockout” with the default settings. There are many factors that can affect this, and fortunately the Victron defaults can be adjusted. To account for my voltage drop, I decreased the “Start Voltage” from 14 to 13 volts, and the “Shutdown Voltage” from 13.1 to 12.8 volts. These setting were recommended by “Offgrid Power Solutions,” on a You Tube video called “Victron Orion-Tr Smart DC-DC Charger settings.”

Cooling is also an important consideration for the Victron because they create a lot of heat, and they derate charging current 3% for every degree above 104⁰ F. That’s almost 50% performance loss at only 120⁰. Maximum operating temperature is 131⁰, where I believe it shuts down completely. This is why I installed cooling fans (but also for the fun of it.)

Amazon’s ”Sound Original” low profile blower fans (two for $9.99) were the right size, they had bearings, brushless motors, and a good mounting configuration for this application. The Victron was mounted on 1/4” standoffs to keep its cooling fins off the mounting surface, and it also helps the fans to distribute air more evenly. I used a Normally Open, 104⁰, 5 amp, thermostat switch to control the fans (Amazon Uxcell KSD9700 (2 for $5.49). The fans get power from the input terminals on the Victron so they can only come on if the truck is connected, and the temperature is over 104⁰. The thermostat switch resets at 86⁰.

The Victron was mounted on a painted plywood board that was attached to the forward battery compartment wall. It’s an easy to reach, out of the way location. I used 4 rubber well nuts that stay in place by themselves, but regular nuts and bolts could be used.

The sheathed #4 cable was terminated to the Victron’s input compression terminals, with the fans power leads. I struggled at first with the Victron’s compression terminations, the wire wouldn’t fit, and I couldn’t find #4 square ferrels. So I was pretty pleased to discover that Anderson pins can be filed down to fit perfectly. Just be sure to cover the exposed barrels with heat shrink.

The negative output of the Victron went to the main chassis ground post under the rear dinette seat where there is a 2/0 cable going directly to the battery negative. The positive output was connected to the line side of a Blue Seas 60 amp fuse block, from there it went to the line side of the existing inverter’s DC circuit breaker, which is jumpered to the battery positive with a 2/0 cable.

With the TV at idle and the lithium batteries around 60%, the Victron output was 35.8 amps as measured by a clamp-on amp meter. The TV input was 42.5 amps. This calculated to 84% efficiency, which is close to Victron’s 87% claim, which I assume is under perfect conditions.

I really liked the looks of the sheathed cable and Trailer Vision plug and receptacle,. The hinged receptacle cover will keep the dirt out when not towing. The plug and receptacle are locked together more securely with the Trailer Vision covers, otherwise the Anderson connectors can be fairly easily pulled apart and they might not stay together on a bumpy road.

Cheers, Geoff