I installed two 300Ah batteries in my trailer with a 12/50 DC-DC charger. I ran a fused AWG 6 wire directly to the starting battery on my 2026 Silverado RST.
The Victron sends 50 amps to the battery bank without any issue, but the starting battery drains quite quickly. It seems that the vehicle’s computer does not use voltage as an indicator to charge the battery. Instead, it monitors the “normal” accessory load and adjusts the alternator output accordingly.
As a result, the starting battery voltage reaches the minimum voltage setting of the Orion, and it stops charging.
For reference, the alternator is rated at 180 amps, and I’ve observed a maximum output of about 60% using an OBD11 device.
Does anyone know a way to bypass the truck’s “smart” charging system so that the alternator charges the battery more consistently?
Sounds like you may need to connect the wire not directly to the battery but infront of the vehicles battery shunt/current sensor. Usually its integrated into the negative pole battery clamp, but measuring positive side is of course also possible, and i dont know how exactly its done on your specific vehicle.
You may also have specific connection points for additional loads, for example ford calls them CCP or customer connection point. By using them the vehicle controls can correctly identify your additional load as a load. This usually leads to the smart alternators voltage output being held at a higher voltage level until the load current drops due to the aux battery being fully charged.
What does that mean “stops charging”, does it go to zero amps after it reached 25A or does it stay at 25A?
13.5V isnt much but with careful setpoint tweaking it should be enough. However, loosing 1V on the cable leading to the Orion is significant. Are you sure that your cable gauge is sufficient for the length?
You may be able to get better performance by using the engine shutdown detection
Especially by setting the shutdown voltage carefully. Thats the point where the input current will be modulated at. Means whenever the input voltage falls to the shutdown voltage, the input current will get regulated gradually, to keep the input voltage at the shutdown level. You can see this between points 2 and 3 in the graph. If the Orion constantly operates in that area it means that the input
It looks like its too small. But that mainly depends on the total cable length.
1V drop is already a lot for a 12V system. Ideally you should stay below 3% voltage drop.
If you calculate the cable gauge through the Victron Toolkit app, for 13.5V input at 50A over a distance of 10m (to and back, since its positive and negative cable) you would need at least 35mm2 to stay within 3% voltage loss, or being left with 12.9V at the Orion. That would be roughly 2AWG.
Pretty sure thats because the input voltage drops below the lockout voltage. Ideally you would reduce the voltage drop, but in a pinch you could also adjust the lockout voltage down. But be aware that this could also lead to the Orion continuing to charge the aux battery while the engine is switched off.
OK, i’ll test the voltage with a VOM. I know the exact voltage on the Victron but not the voltage at the alternator output( analog meter in the digital dash) I’ll also check the resistance of the fuse box and connectors ( I have flood the connector in solder instead of crimping it.)
I still dont understand why people think thats a good idea. Everywhere electrical connections get crimped or pressed, from 0.1mm2 to 630mm2. Solder wicks along the individual strands back into the wire, making the first section at the connector rigid. Thats detrimental in mobile applications, or general where vibrations are common. Id personally start there, pulling on the cables to see if the copper core broke where the solid part goes over into the flexible