Problem with voltage sag on 10S5P (LG HG2)

Hi guys,

After running into over voltage faults last week I decided to rewire my BMS to only use it for charging. Since then I’ve noticed some unusual voltage sagging. Could my rewiring of the BMS have caused this? Do you guys have any idea on how I should proceed to diagnose the issue?

Here is the same ride, before and after my changes:

It gets really bad towards the end…



Can you post pics of your current BMS wiring and maybe draw a diagram how it was wired earlier?

Goes down from 40v to 33v with 2 times over voltage (from hard braking i assume)? Can’t see the “sag” in your charts.

Maybe I’m confused about voltage sagging, I’m concerned about the voltage jumping a lot between 34V and 40V, it does not look as stable as it used to. On the first ride, voltage was super steady, on the second ride it’s all over the place…

Ok now i see, thats the opposite of voltage sag^^ could be from hard breaking too. Lowering max regen brake current could help but would result in weaker brakes.

Towards the end, there’s little spikes because you are braking, look at youbcurrent, it will be negative

Ok that makes sense, I guess the BMS was preventing these spikes before… Is this going to be a problem for the battery?

Don’t think so, hg2 is rated for 4A max charging current. So for 4P that would be 16A (4*4). Can’t see that much in your chart. Anyways you should set max charge current @16A or maybe bit lower for longer battery life. Edit: 4P is mine^^ 5P is 20A of course :stuck_out_tongue:

Thanks, I’ll do that.