My DC to DC charger barely charges my lithium batteries on my trailer. With truck engine running I get 12.8v at the battery and at the 7 pin connector, however voltage to the Victron charger will suddenly drop to 11v or lower and then bounce back up. By lowering the input voltage lockout I can get it to charge steadily at around 13.5v. The Victron app says it is charging in bulk mode but the smart battery app shows a charge rate of only 15.8w at 1.2 amp. Battery is at 40% SOC and says it will take 47 hours to reach full charge! I have followed instructions in the installation and used the fine multi strand 8 ga wire recommended. I have checked my connections and it all seems fine. I cleaned the terminals on the 7 pin. Where is the problem?
I use a 12-12-18 on my boat and 8AWG. The distance to the charger from the battery is 3m, and the distance from the charger to the battery is 0.5m. What you might need is 16mm² and an Anderson plug on the back of the car to the trailer. Take some measurements and check out the Victron Toolkit app to see what voltage drop you are getting with the current length and cable size.
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Your Orion is operating between points 2 and 3 of the diagram
The input voltage was high enough to start charging, but once current was flowing over the input cabling, the voltage loss across it lead to the input power getting limited.
Reduce input cabling resistance. If it once worked, then theres some contact point that went bad. Otherwise increase wire cross section
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Thanks for the replies. I chose the 18 amp Victron mainly so I could avoid running new wire from the tow vehicle battery back to the junction box on the trailer. Everything I read said the 18 amp unit would work fine with the existing wiring. This is my 2nd unit. I couldn’t get the 1st one to work either so assuming something was wrong with it I sent it back. My truck is a 2018 F150 with a smart alternator and factory tow package. I guess it’s back to running more wire and an Anderson connector.
One thing that is confusing to me is the cable size nomenclature. I am only familiar with the AWG sizing and do not know what is the equivalent to the mm2 sizing. What is the AWG size of 16mm2?
You should be able to use Google in the usa, dont you…
It should be about 6AWG, the largest you can fit in the unit and a 50A Anderson.
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I removed the 30A breaker I had on the output line and now get a charging rate of 40W @ 3A. The charger also no longer toggles on & off due to the input lockout but this still seems like a very low rate of charge.
I guess I still need to beef up the wiring?
Yeah, that is no good, and breakers are very high resistance, just use a fuse like a midi, mega, or ANL. They are very low resistance. When mine is running, I get the full 18A out, and the input current is around 21A.
Thanks for the advice on fuses vs circuit breakers Owen. The problem is I bypassed the circuit breaker and although it doubled my output it is still only 40 watts @ 3 amps. Assuming that my truck is wired to the 7 pin with 10 AWG for the pos & neg leads my output should be much higher. I have read accounts of this 12-12-18 unit putting out up to 24A from the 7 pin connector - all with no modifications to the wiring on the tow vehicle or trailer lead in cable. I’m going to check the 7 pin next to see if the battery wire is actually 10 AWG.
These units are voltage-sensitive and aren’t designed to be loads themselves. They need virtually zero voltage drop to operate accurately because they’re constantly monitoring voltage to determine their operating mode. When they draw power, voltage drops - when they supply power, voltage rises. This creates a feedback loop that can confuse the control logic.
I had to emergency-charge a 5A BMS lithium battery with my 12-12-18 once. The trick was adding a really long output cable, which created enough voltage drop and resistance to limit the current draw. This fooled the unit into thinking the battery was nearly full, so it dropped into absorption mode and reduced the charging current to a manageable level.
Thanks Owen, I’m trying to understand what you meant about the units being voltage sensitive. Now, should I go with larger gauge wire and an Anderson connector? Apparently other folks have had success with the standard 10 AWG from the truck back to the Victron.
Here is an account of someone with a 12-12-18 unit working just fine with 10 AWG wiring from his Ford truck.
If you are using the 7 pin 10ga 30amp rated wire just to “top off” or add whatever charging is possible while underway like I did, consider installing it in/on the 5er in the rat’s nest of wiring that is typical on most RV trailers. I’ve achieved up to 24 amps of charge while underway through my Victron 12-12 DC/DC 18 isolated charger for my measly 200a/h LiFePo bank. Judging by the size of the wire connection slots on the Victron, it would be tricky to get a much larger wire connected, like some do by running a dedicated circuit of heavy wire from the engine bay of the truck to an Anderson connector at the rear bumper with a corresponding connector at the 5er front. That is a more advanced installation I can’t help with.
I used the “square” ferrule wire terminals to maximize the size of wire and security of the connection between the charging wire on the 7 pin and the connections to the positive and negative busses in the wiring locker/rat’s nest. The vacant input slot is for the 7 pin charge wire which I terminated with a ferrule at final installation. I used wires larger than the 7 pin charging wire for the rest just because.
Not sure how he is getting 24amps out of 18amp charger. Maybe he is measureing the input or has a typo. Maybe its 2-4 amps?
I mentioned previoulsy I am using 10awg wire for mine and have 3m from the battery and 0.5m to the battery so the voltage drop is very small. My alternator puts out 14.4V up to 65A. Its on an outboard spends a lot of time at tidle or 1500-2000rpm so the 18A is prefect.
You need to check the wire size and length. If you do want to go to anderson plugs 6awg fits the 50A and also the largest size that will go into the Orion charger. It take 16mm2 or 6AWG as the max size.
If you do find the wire is small maybe look at the Bluetti Charger 1. Its a 560w universal MPPT charger. It puts out up to 56V at 560W and is adjustable to what you need. You will need to replace the DC-DC with an MPPT. That is an option if the wire is small. As you raise the voltage the current goes down.
OK, I found the problem. I had read that the the pos & neg battery pins on the 7 pin connector on my truck were 10 ga wire but they were not. The - wire was heavy, possibly 10 ga but the + wire was a thin 14 ga or smaller.
I ran a 10 ga (6mm2) wire from the battery, fused @ 30 amp, to the rear of the vehicle and ran 10 ga wire along the trailer cable to the input on the Victron. I ran the + wire from the 7 pin to to the H terminal on the remote on/off on the Victron so the charger will turn off when the engine is off. I used 10 ga wire instead of heavier because I had 2 20 ft extension cables with connectors from a Renorgy portable solar panel I had purchased. I never used the extension cables anyway. I ran only a + wire since the - wire on the 7 pin is 10 ga and the hitch & safety chains provide additional grounding.
The results? I now get 13.9v charge out of the Victron and my 2 LiFePo4 batteries charge at 146w @ 11a for the battery closest to the charger and 82w @ 6a for the 2nd one. Can I then assume that the total charge rate is 228w @ 17amps? If so that is good enough for me since our fridge is propane/ac.
Thanks for the help offered by this forum. I see now that I should have checked the wiring at the 7 pin earlier as chrigu and Owen suggested.
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