So if it's not too late for OP (and for future reference) here is how I did mine with e-torque.
First off, let me say I did NOT use Renogy DC-DC mppt charger. I used a Victron Isolated DC-DC charger/ converter instead. I found that to be the simplest solution to this problem. I also have this inside my cab instead of on a trailer ( I dont own/ tow a trailer... but that may change in the future) since everything I need for camping/ overlanding is self-contained to my truck. I have a 3kw EcoFlow setup in the back seat that is charged by Victron, so I run the ign wire to the fuse box inside. Even though my application is different, the principle and the way it works are the same.
@PeterB I do have something hooked to engine bay fuse box that is IGN switched. I don't have my truck right now and I forgot which one it is. I will check for you tomorrow when I drive the truck to work. Alternatively, you can also use a multimeter to find it.
Now, with all that out of the way. Let's start with how I did it.
Parts needed:
- Blue Sea 60A circuit breaker (you can use inferior Chinese branded ones if you want, but I strongly recommend not. Chinese branded ones or Chinese made ones that are NOT made made for US or EU companies have a lower energy rating)
- 8 Gauge Wires, power and ground
- Spool of 14 Gauge Wire and Micro2 Fuse Tap
- 5A Micro2 fuse
- Wire Looms
- Ring Terminal Connectors for both 8Ga wires and 14ga wires.
- Victron Isolated DC-DC Chargers
- Blue Sea Bus Bar and Fuse Block w/ Ground (both optional, but recommended)
Brief overview of how I did it.
- Decide and mount each component you will be using, such as the battery, the DC-DC charger, fuse block/ bus bar, etc.
- I ran enough 8ga wires from the battery to where I want to install my Fuse Block with Ground, both power and ground. Also run one 14ga wire for IGN and add the fuse tap for the applicable fuse slot.
- I then added the circuit breaker for the power side near the battery. This will serve as an on/ off switch and a layer of protection in case something goes wrong, it will cut itself out and not affect the functionality of the truck.
- Sleeve the entire harness and secure it.
- Run one 14g power and ground from the fuse block w/ ground to the Victron. This is actually the preferred way for 2 reasons: 1)You can add a solar controller later down the line and hook it to the fuse block, if you choose to. 2)You will have a secondary safety (fuse) here in case something fails.
- 14g is ample for Victron's usage. Victron is actually a regulator that can step 12v input up to 24v or even 48v output if faster charging speed is needed.
- You do not need to use a 8g wire for Victron because you're not drawing power directly from the alternator. You're actually drawing from the battery itself, so there's no power surge or anything like that to consider.
- Connect the IGN trigger and download the Victron app. Switch to "charger" mode and enable engine shut down disable.
- Charger mode is the only mode that allows engine shutdown detection
- Engine shutdown detection will detect no current being sent through IGN, and therefore will isolate the output. That way you will not draw any power from your starter battery.
- Also enable smart alternator and start up delay. That will give some time after starting the vehicle before Victron starts to draw power to avoid that initial start up current hike.
Normally, it is NOT recommended to run dual battery setup with different chemistry batteries. However, with smart converter like Victron that has dedicated profiles for different house battery (secondary battery), I think it should be OK.
Benefits of running the Victron:
- Smart controller
- Built in profiles, engine shutdown detections, charging cycles, etc
- Fast charging
- With my setup and using XT60i cable as output cable to my Ecoflow, I can get 200w of charge rate. with output set to 13.3V at 15amp. I get 210w of charge rate when output is set to 14v at 15amp. Not much difference. But with another unit (that I have sitting in the garage), I can bump it up to 24v @ 15amp output netting me about 360w of power.
- All-in-one design
- This is the only thing you will need in addition to the battery.
- Smart phone integration
- All settings are done via app and you can monitor it any time.
I will have a detailed write up some time in the future, when I get to taking photos lol
Additional Info:
- Lithium batteries require higher voltage (high 13s and low 14s) to be happy. E-torque does not constantly put out that much. In fact, e-torque keeps the starting battery voltage relatively low at high 12s to low 13s. Those are not enough to keep lithium battery happy. Therefore, a smart DC-DC charger is needed to manage the charging. This is exactly why a lot of "dumb" dual battery systems will not work with ours unless both batteries are switched to the same chemistry.