Hi all, newbie here, I am currently attempting to install a 12-12 30 Orion-Tr Smart Charger Isolated into my 2012 Mercedes Sprinter Van, using the charger to take current from my van starter battery and pushing it to my 2 100AH Lithium Ion house/leisure batteries.
I am wondering if I need to be making my Input negative connection directly to the starter battery negative terminal or if I can be grounding it to the chassis, and if I can ground it to the chassis if it matters where that chassis ground is (closer or further from the starter battery). I am looking to minimize voltage drop in the circuit for best performance delivering a charge to my house/leisure batteries.
I called Dragonfly Energy (Battleborn) energy and they recommended connecting directly to the negative starter battery post, and this seems in accordance with the orion install instructions provided with the unit. They also mentioned grounding to the chassis instead of the starter battery stud could result in issues.
However, after some research on this form and others, I am getting conflicting information on the topic. There are other posts on this and on Sprinter Forum and this site that recommend either installing to the factory ground stud underneath the driver seat box or a separate ground.
Ex.
- https://sprinter-source.com/forums/index.php?threads/102362/
- Mentions Mercedes Upfitter guide recommends against connecting directly to negative post for interfering with other electronics. Action recommended: Ground to Chassis stud under seat post
- https://sprinter-source.com/forums/index.php?threads/86193/
- Battle Born Cited: "You are able to wire the isolated version with a chassis ground for the input negative"
- This one is interesting because this is different that what was recommended to me when I called Battleborn.
- Battle Born Cited: "You are able to wire the isolated version with a chassis ground for the input negative"
- https://community.victronenergy.com/questions/51355/common-ground-connection-with-isolated-dcdc-charge.html
- Cites grounding will work on isolated version
Given the above context, I find it confusing with the seemingly conflicting install guidance. Could anyone shed some light over why or why not I would connect the input negative for the orion to a ground vs connecting to starter battery stud. Tradeoffs grounding near my leisure batteries (I created a ground in the rear for this system) vs running cable back to the factory ground stud closer to the starter battery? If grounding to the rear, how does that affect my calculations for AWG sizing (if i can cut wire run by grounding to the rear, can I run smaller AWG since the "run length" is shorter?) Thanks so much for the consideration!