Various battery states

[The Rookie]

While poking around today, I noticed while watching the battery BMS via BT that when I start my engine there is a decent draw. I thought that was interesting, so I ran a few settings (no shore or genny power for all):
Pic 1: eng off, in store position

Pic 2: eng off, in use position

Pic 3: eng running, in store position

No pic: eng running, in use position- basically same as Pic 3

I have a BIM 160, so I would have assumed that the higher voltage on my LFPs would have kept the batteries separated.

Any insight?

 

[16ACE27]

I would have assumed that the higher voltage on my LFPs would have kept the batteries separated.

No, that would keep your battery banks connected, even when not connected to SP

 

[The Rookie]

Ahhhh, that makes sense. They stay connected whenever there is a charging current detected and seperated when there isn’t anyone? But why would I see the draw against the house batteries when starting the engine?

 

[16ACE27]

why would I see the draw against the house batteries when starting the engine?

You have two voltage sources connected in parallel: One at a resting voltage of 12.7 VDC and one at 13.6 VDC. The 13.6. VDC is pushing current harder than the 12.7 VDC so it will try to take the majority of the current until the two source voltages are equalized by internal and external resistances while drawing the starting current.

 

[The Rookie]

This is great info, thanks ACE.