HV battery voltage is dropping.

[gozer]

I've had a'22 S for about 2 weeks now and every time I charge the voltage on the traction battery drops lower than it was on the previous charge. LS now says its at 362 volts. when I bought the car it showed 392.
mV diff is 13 between cells. 14 QC's car has 15k miles. average is 3.78 volts per cell. What is going on? Car runs fine.

 

[Stanton]

Any additional history/details for the car? If not, posting a LS cell voltage screen shot may help.
Both the overall voltage and average cell voltage seem low; if you can't get the cells over 4.0v on a full charge, then something is going on with the BMS (or a rogue cell).

 

[gozer]

I dont know how to post pics from LS, I'm not that tech savvy. There arent any very low cells on LS, 13mV is the max difference between, but things move alot while underway, still no huge spikes. It was a leased car, it is CPO there is nothing in the maint history about the HV. The histogram on LS has a large spike but I think its only the scale. It reads Min=3.772 max=3.784 ave =3.778. 12 mV. Its in the 40's here in the morning (upstate NY) and 50's-high 60's in aftn. I drive mostly on the highway 60-70mph 50 miles oneway.

 

[gozer]

I've tried to stay away from 100% charging, been mostly 80-95% max. Could some QC's help? (240v vs 400v) I'm not convinced how capable the dealer is w BEV's, so I hesitate to go there unless really needed.

 

[nlspace]

I've tried to stay away from 100% charging, been mostly 80-95% max.

That is why you are only seeing 362V for the pack. If you want to see 392, then you need to let it charge on up. Drive it down to below 2 bars, then let it charge up and balance at 100% to do a calibration charge.

 

[gozer]

Sorry for the newbie question, but will it balance when it reaches 100% or should I let it sit, plugged in, at 100% to balance?

 

[nlspace]

Leave it plugged in until it stops (turns OFF the EVSE) on it's own. Balancing is done by bleeding off the higher cells. It may stay in charging mode in order to add a little bit as needed to bring up the laggards, then burn down the leaders. But it is very slow because the bleed current is only about 10 mA.

 

[Chad E. Mo]

(Apologies to those who have seen my chart before.)

This is data from my feed to the EVSE on my SV+. Note the pause-charge-pause-charge at the end of the cycle. I believe the pauses are for balancing resistors to bring the high cells down before bringing the entire pack up again.

I charge to 100% from ~50% at least three times a week. My max dif is typically ~10mv.

 

[gozer]

Well THAT worked!
403 volts!
Blue lines for all cells!
Guess I'm doing that again!

 

[gozer]

Oh, yes, mV was down to 6. Nice!

 

[Steve52]

Well THAT worked!
403 volts!
Blue lines for all cells!
Guess I'm doing that again!

There's really no need to be concerned about the voltage on the HV battery, if your SoH and Hx are good and the car has the mileage you expect, there is nothing wrong with charging to 80-95% as you had been doing.

 

[gozer]

OK, Good to hear, I will not always be able to get to 100%. Thanks for all the help, guys. A newbie in a new method of transit needs the support. Thanks , again!