Add ramped charge value for Tesla #100

dalathegreat · 2023-11-19T20:04:58Z

What

This PR adds a new feature for Tesla batteries, smoothing of charge max value for when battery approaches 100%

Why

@Newevg noticed that when trying to charge their LFP Tesla battery to 100%, charging it with 15kW all the way up to 100% was not possible. To reach 100%, the charge needs to taper off, otherwise the contactors would open, and the BMS would flag a fault.

How

The .header file now has a configurable max value, MAXCHARGEPOWERALLOWED. This value, which defaults to 15000W, will be used when battery is between 0-95%. When battery reaches 95%, it ramps between MAXCHARGEPOWERALLOWED-> 0 in the 95-100% range. This should allow the battery to more gracefully reach 100%.

matvey83 · 2023-11-21T16:50:00Z

Software/src/battery/TESLA-MODEL-3-BATTERY.cpp

@@ -156,7 +156,7 @@ static const char* hvilStatusState[] = {"NOT OK",
 #define MIN_CELL_VOLTAGE_NCA_NCM 2950   //Battery is put into emergency stop if one cell goes below this value
 #define MAX_CELL_DEVIATION_NCA_NCM 500  //LED turns yellow on the board if mv delta exceeds this value

-#define MAX_CELL_VOLTAGE_LFP 3450   //Battery is put into emergency stop if one cell goes over this value
+#define MAX_CELL_VOLTAGE_LFP 3500   //Battery is put into emergency stop if one cell goes over this value
 #define MIN_CELL_VOLTAGE_LFP 2800   //Battery is put into emergency stop if one cell goes over this value


Change "goes over this value" to "goes under this value".

Fixed in 6801e83

matvey83 · 2023-11-21T17:03:23Z

Software/src/battery/TESLA-MODEL-3-BATTERY.cpp

+  } else if (SOC > 9500) {        // When battery is between 95-99.99%, ramp the value between Max<->0
+    max_target_charge_power = MAXCHARGEPOWERALLOWED * (1 - (SOC - 9500) / 500.0);


Since SOC is different from real SOC of the pack, this ramp will need to change depending on the difference between these 2 as well. For example, if the user only wants to change the battery to 70% real SOC (which will be 100% inverter SOC) we may not even need the curve.

So I think this needs to be re-implemented to take the value of MAXPERCENTAGE into account.

But even better, ideally what we want to do a feedback loop that looks at the voltage of the most charged cell group and scale down charge power to bring it slightly below the max voltage, and scale up charge power if the voltage gets lower than (max voltage - some threshold). That is the most efficient way to charge a battery. Even if MAXPERCENTAGE is something like 80% this method will ensure that the pack will be charged the quickest to that SOC.

I think we should ignore the SOC that the battery reports (which is based on a calculation) and just go off max cell voltage for the ramp.

Max cell voltage will be proportional to charge speed, so basing the ramp on max cell voltage might cause oscillations.

I instead propose we use SOC_VI for the ramp. That way incase user limits battery to between 20-80%, the value will never ramp. And incase user extends the range closer to 0-100%, we will use a ramped value at the extremes.

OK makes sense, basing the ramp on the real SOC is the way to go. Also how is the 95% number derived? Seems like this number will change based the max charge power and battery capacity. So for some configurations we may want to start ramping at 90% for example.

@matvey83 The 95% number comes from watching multiple different battery vendors throttle charging at end of SOC%. Fastcharging usually starts throttling at 80%, but AC slowcharging is ~95% where it starts to taper off.

dalathegreat · 2023-11-21T19:17:46Z

@matvey83 and @lenvm , I reworked the ramp logic to avoid having users that restrict their battery encounter slow charging.

I also added an extra safety check in bf292a1

lenvm · 2023-11-21T20:13:19Z

Software/src/battery/TESLA-MODEL-3-BATTERY.cpp

@@ -193,12 +193,17 @@ void update_values_tesla_model_3_battery() {  //This function maps all the value
  } else {
    max_target_discharge_power = temporaryvariable;
  }
+  if (SOC < 20) {  // When battery is lower than 0.20% , set allowed discharge W to 0


Instead of hardcoding the value 20 (representing 0.20%), shouldn’t this be based on MINPERCENTAGE?

I would also change these lines into one if, else if statement that defines the max_target_discharge_power, rather than two separate if statements.

Additionally let's define MAXDISCHARGEPOWERALLOWED as 60000.

Suggested code:

// Define the allowed discharge power max_target_discharge_power = (max_discharge_current * volts); // Cap the allowed discharge power if real SOC is lower than the minimum percentage, or discharge power is higher than the maximum discharge power allowed if (soc_vi < MINPERCENTAGE) { // When real SOC is lower than the minimum percentage, set allowed discharge power to 0 max_target_discharge_power = 0; else if (max_target_discharge_power > MAXDISCHARGEPOWERALLOWED) { max_target_discharge_power = MAXDISCHARGEPOWERALLOWED; }

This also removes the need for the temporaryvariable.

Additionally I would like to suggest to define, in another pull request, a convention how SOC and other percentages are defined, either 20.0% as 200 (as is the case for MINPERCENTAGE and soc_vi), or 20.00% as 2000 (as is the case for SOC), such that we don't make conversion mistakes.

@lenvm fixed in e2d3c4f , I decided against using MINPERCENTAGE, and going for the simpler if SOC=0 check, since that is what other battery types use! Nice bonus with the temporaryvariable removed!

lenvm · 2023-11-21T20:19:51Z

Software/src/battery/TESLA-MODEL-3-BATTERY.cpp

+  if (soc_vi > 950) {  // When battery is between 95-99.99% real SOC, ramp the value between Max<->0
+    max_target_charge_power = MAXCHARGEPOWERALLOWED * (1 - (soc_vi - 950) / 50.0);
+  }
+  if (SOC == 10000) {  // When battery is defined as 100% full, set allowed charge W to 0


Instead of two separate if statements, I suggest using one large if, else if, else statement:

if (SOC == 10000) { // When SOC is 100%, set allowed charge power to 0 max_target_charge_power = 0; } else if (soc_vi > 950) { // When real SOC is between 95-99.99%, ramp the value between Max<->0 max_target_charge power = MAXCHARGEPOWERALLOWED * (1 - (soc_vi - 950) / 50.0); } else { max_target_charge_power = MAXCHARGEPOWERALLOWED; }

Good improvement, fixed in 36deffd

PR changed

lenvm · 2023-11-21T21:43:23Z

Another way to implement the charge power limit, is to use the charge limit that is reported by the battery on CAN.

According to this repository, message 594 = 0x252 reports the BMS charge and discharge limits.

0x252 is already read from CAN, including the BMS charge and discharge power limits, in https://github.com/dalathegreat/BYD-Battery-Emulator-For-Gen24/blob/baa7841f324ab6b21207d3e9aab67eac3c71d250/Software/src/battery/TESLA-MODEL-3-BATTERY.cpp#L376-L377

Can these values not be used directly as max_target_charge_power and max_target_discharge_power?

dalathegreat · 2023-11-22T20:04:51Z

@lenvm For some reason the Tesla packs are not satisfied, and will show 0kW on regenerative_limit

So this is why we need the ramp, for now!

dalathegreat added 3 commits November 19, 2023 20:31

Add ramped charge value for Tesla

3aa3d8e

Raise max voltage per cell LFP

19e3372

Tweak ramp if-statement

1e91bd6

lenvm previously approved these changes Nov 20, 2023

View reviewed changes

Fix division error

2f6d6cf

matvey83 reviewed Nov 21, 2023

View reviewed changes

dalathegreat added 2 commits November 21, 2023 21:13

Rework ramp logic

6801e83

Add discharge SOC% safety

bf292a1

lenvm reviewed Nov 21, 2023

View reviewed changes

lenvm self-requested a review November 21, 2023 20:21

dalathegreat added 2 commits November 22, 2023 22:13

Rework ramp logic

36deffd

Rework discharge calculation

e2d3c4f

rjsc approved these changes Nov 22, 2023

View reviewed changes

rjsc merged commit 65a126d into main Nov 22, 2023
32 checks passed

rjsc deleted the feature/charge-ramp-tesla branch November 22, 2023 22:14

rjsc restored the feature/charge-ramp-tesla branch November 22, 2023 22:50

rjsc mentioned this pull request Nov 22, 2023

Revert "Add ramped charge value for Tesla" #107

Closed

dalathegreat deleted the feature/charge-ramp-tesla branch November 25, 2023 09:23

Provide feedback

Saved searches

Use saved searches to filter your results more quickly

Add ramped charge value for Tesla #100

Add ramped charge value for Tesla #100

dalathegreat commented Nov 19, 2023 •

edited

Loading

matvey83 Nov 21, 2023

dalathegreat Nov 21, 2023

matvey83 Nov 21, 2023

dalathegreat Nov 21, 2023

matvey83 Nov 21, 2023

dalathegreat Nov 22, 2023

matvey83 Nov 27, 2023

dalathegreat commented Nov 21, 2023

lenvm Nov 21, 2023 •

edited

Loading

lenvm Nov 21, 2023 •

edited

Loading

dalathegreat Nov 22, 2023

lenvm Nov 21, 2023 •

edited

Loading

dalathegreat Nov 22, 2023

lenvm commented Nov 21, 2023 •

edited

Loading

dalathegreat commented Nov 22, 2023

		} else if (SOC > 9500) { // When battery is between 95-99.99%, ramp the value between Max<->0
		max_target_charge_power = MAXCHARGEPOWERALLOWED * (1 - (SOC - 9500) / 500.0);

Add ramped charge value for Tesla #100

Add ramped charge value for Tesla #100

Conversation

dalathegreat commented Nov 19, 2023 • edited Loading

What

Why

How

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

dalathegreat commented Nov 21, 2023

lenvm Nov 21, 2023 • edited Loading

Choose a reason for hiding this comment

lenvm Nov 21, 2023 • edited Loading

Choose a reason for hiding this comment

Choose a reason for hiding this comment

lenvm Nov 21, 2023 • edited Loading

Choose a reason for hiding this comment

Choose a reason for hiding this comment

lenvm commented Nov 21, 2023 • edited Loading

dalathegreat commented Nov 22, 2023

dalathegreat commented Nov 19, 2023 •

edited

Loading

lenvm Nov 21, 2023 •

edited

Loading

lenvm Nov 21, 2023 •

edited

Loading

lenvm Nov 21, 2023 •

edited

Loading

lenvm commented Nov 21, 2023 •

edited

Loading