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Apologies - not sure how to add this post in to the relevant index section for Hyper 9 builds. Please tell me if I can/should post it elsewhere.

I am using 5 Tesla modules in series. I consider fully charged to be 4.2V per cell (which I know is right at the top limit) and I consider totally discharged to be 3.0V (again, right at the limit). These are the limits I have set in my Orion BMS2, and anything outside these limits will cause the Charge/Discharge enable relays to open and a fault code (hard shutdown), so I never want these limits to be breached.

On charging, the Orion will stop the charger if a cell hits 4.2V, so in practice my pack never gets to 126V. I have managed 125.5V, which then settles a bit once charging has stopped.

On discharge, the Orion will cut all relays if a cell hits 3.0V, so in practice this can happen when the pack voltage above 90V due to different cells at different volages.

I have 'decided' that 0% SOC should be 99V, or 3.3V per cell, to give me lots of buffer for safety.

Question 1 - is 99V too high for 0% SOC?

I have noticed that there can be considerable voltage sag if one accelerates hard and pulls large current. I have not attempted to pull the 800A that I've seen on the 4Foxtrot graph, but I have seen 3-5V pack voltage sag at times. I want to know that I can hit the 'gas', and the sag will not drop the voltage low enough to cause the BMS to cut out. Hence I think 99V should be OK. Obviously I can keep driving at this point provided I keep the current draw low and gradual (ie 'limping').

Question 2 - The pic below shows my battery protection tab in the Tau software. I intend for 'normal', ie not de-rated, current supply between 94.5V - 125V, to allow for a little sag. Any comments on my chosen values below?

122674


And Question 3 - does anyone use a cutout for low cell voltage? I am thinking I will use the Orion to interrupt my throttle at (say) 3.1V (93V pack). That way I should never have the Orion cut all discharge and enter a fault state (at 3.0V) due to inadvertant voltage sag. The ACX1 is only looking at PACK voltage, not CELL voltage, so I would like a way to ensure the low cell fault state can't be 'hidden' by the pack voltage 'average' effect of summing all cells.

Thanks for reading!
 

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I have been super busy with other projects, so I have not had time to work on dialing in these settings on my build. I feel like I left a slightly larger margin of error on the top end to limit the regen. I forget how much I did. The cells in my packs are probably similar to yours, but I am going to cut things off at 4.1v/cell to give myself a bit more cushion. Also, my BMS is set up to sound an alarm if the voltage drops too low, but it doesnt ever cut off the power. I am still not sure where to put my thresholds to account for sag, though. Anyway, I have not been any help, but I did add this to the Hyper 9 thread index. Hopefully someone will chime in, and I will try and post my findings when I get a chance to do more testing.
 

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Might help: (pasted from my notes)
Voltage SAG
(TMC) "260 volts is what my 1525 amp P85DL makes at 30% and 110F/43c" on a full tesla 16 module pack so 16.25v / module = 2.7v / Brick & Cell !! = 81.25v on my 5 module / 30 brick/cell pack . Tom de Bree/Zero EV: have taken sag down to 2.5v / cell.
SO I set Minimum's on my 5 module pack as absolute MIN with sag: 82V (2.73v) and absolute MIN at steady state 94v (3.13)
 
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