Lithium House to Alternator Setup

[Waxwing]

This is a partial schematic, but before it gets too busy, I wanted to run the basic setup by the crowd. Big picture - House bank connected to alternator, start batt to starter and charged by DC-DC charger. All batteries are LiFePO4, the starter batt is a dual purpose crank batt.

System - 3X 200 Ah Dakota LifePo4 House Batteries connected to the 120 Amp Mahle Alternator via Lynx Power Distribution. 1X 60 Ah Dakota Li 1000CCA Starter Batt connected to the Starter (+) and Block (-), charged via DC-DC Victron Orion XS 50amp charger. The alternator will be protected from overheating by using a Wakespeed 500 external regulator and protected from BMS shutoff with a Sterling Alternator Protector.

Question - As you can see from the schematic, I have the Lynx Distribution Bus connected to the engine block for common ground AND I also have the Engine Start Batt connected to the engine block common ground, NOT the Lynx Distribution Ground.

Reasoning is keep the start circuit on big cables and short run. The DC DC charger can accept a max of 4 awg negative.

Is this ok, or have I created two paths to common ground for the system?

Sorry for the orientation, can't seem to get it right side up.

I have downloaded and turned it 90' using MS Paint. Regards Pete7

[Pete7]

Looks good. We have used the Lynx Power In as well. Neat way of bring it all together.

Make sure the 3 sets of leads from the Dakota LFPs are all the same length.

Perhaps one minor, can you put the neg for the alternator return currently connected to the engine block on the alternator so all the current goes directly through copper rather than the block and then run a smaller wire to the engine bloke for any temp or pressure switches?

Not familiar with a Malhe alternator, is it external regulated so it doesn't over heat charging the Dakotas, particularly at low engine revs when there isn't much cooling air flowing through the alternator?

[Waxwing]

Thanks Pete7. Yes, all batt cables will be same length. The Mahle alternator grounds thru bolting to the block, so I am planning to have the Lynx power distribution negative attach there. Just wasted to be clear that the system is grounding to the block in twice.

Here is the full meal deal...

[wholybee]

I am sure its fine and you won't have any problems. But best practice is to only have one connection to the engine block.

The only reason the engine is grounded is for the engine, the starter, sending units, etc. are all grounded through it. Some alternators are not, and would have a separate ground wire.

Anyway, I would not connect the house ground bus to the engine. Instead, I would run a wire from the house ground bus to the starter battery negative. It only needs to be large enough to handle the current of the DCDC charger. You could use a bus bar for the starter negative for this to avoid multiple connections directly to the battery terminal. But as long as the heavy starter cable went on first, the connection could be directly to the battery.

I don't really see a technical reason your way wouldn't work. It might increase wear on you shaft anode, because charge current from the DCDC would be going through the engine block, but that is a complicated subject, so I can't say for sure.