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CANADA, UNITED STATES Document ID: IK2300038

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ISIS, Bus ISIS, IsSIR

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1

Major System:

ELECTRIC VEHICLE

Created:

3/21/2025

Current Language: English

Last Modified: 1/20/2026

Other Languages: NONE

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Ryan Hendrickson

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Title : Electric Vehicle State of Charge Calibration
Applies To : All Electric Vehicles
CHANGE LOG
Please refer to the change log text box below for recent changes to this article:
1/20/2025 - Added Note in Diagnostic Step Section.
04/23/2025 - Initial Article Release.

DESCRIPTION
This document will walk the user through correcting the battery State of Charge (SOC) calibration.
It has been found on some electric vehicles that the SOC calibration can become incorrect over time. Often times this is from the vehicle sitting a
long period without use or charging the batteries. This will result in the SOC value on the cluster becoming inaccurate compared to the SOC value
in the battery packs. This may also result in a low value for the vehicle range estimate on the EGC.
SYMPTOMS
Estimated range remaining displayed on the cluster is low for the given remaining SOC.
SOC decreases significantly faster than expected while operating the vehicle.

DTC/Light

Description

N/A

N/A

SPECIAL TOOLS / SOFTWARE

Tool Description

Tool Number

Service Diagnostic Solutions (SDS)
Electric Vehicle “Y” Adaptor Cable

08-801-01

Nexiq USB 2 or Nexiq USB 3
Electric Vehicle “Y” Adaptor Cable 08-801-01 must be used when diagnosing and recording signals with SDS.
The EV Y adapter cable can only be used with the NEXIQ USB2 or NEXIQ USB3 adapter.

SERVICE PARTS INFORMATION
Kit Description

Part number

Qty. Required

Notes

N/A

N/A

N/A

N/A

DIAGNOSTIC STEPS
WARNING: To prevent personal injury and / or death, or damage to property, NEVER service a high-voltage vehicle without completing
High-Voltage Safety training. Before working on vehicle, read and obey High-Voltage Safety, and Lock-Out Tag-Out safety procedures
and information.
NOTE: It is a good practice to confirm the BMS calibration is up to date. Please review IK4300030 for instructions on updating the BMS.
Pre-Entry conditions
No DTCs related to batteries, cell voltage, or State of Charge (5919-x, 5923-x, 8100-x). If there are DTCs for these items please follow the
appropriate FCAP/GUIDE for the DTC.
Battery health report can be taken at any SOC if the vehicle cannot be charged or driven. It is preferred that the SOC be either 30-50% or 90100% for the most accurate results. It is preferred that we do not evaluate the SOC in the 60-65% range.
After driving/charging the vehicle will need to be parked with the key off for 60 minutes or more. When the key is turned on to connect
with SDS be sure to turn off all additional loads such as fans, heat, A/C, lights, etc. The purpose of waiting 60 minutes after any charging or
load being placed on the batteries is to allow the pack voltages to stabilize.

Step Action
DIAGNOSTIC:
1

Using IK4300027, capture a battery health report.
Open battery health report and review values for battery pack temperatures,
see figure 1 below.
Are all values at 50°F (10°C) or above?

Decision
Yes. Continue to step 2.
No. Charge/drive the vehicle to warm
batteries. See section Warming the High
Voltage Batteries below (Link). Then repeat
key off 60 minutes and retest this step.

Figure 1: Battery Health Report (example)
Item 1: High Voltage Battery Current Draw
Item 2: Cluster Display SOC Value
Item 3: Average High Voltage Battery Pack Temp
Item 4: High Voltage Battery Pack Voltage
Item 5: Average Cell Voltage

Step Action

Decision

2

Yes. Continue to step 3.

DIAGNOSTIC:
Using the battery health report, review the high voltage amperage draw.

Is the value at 1.5A or below?
No. Open a technical service case file and
share the battery health report on the
case.

Step Action

Decision

DIAGNOSTIC:
3

Yes. Continue to step 4.

Using the battery health report, review the battery pack voltage and SOC values
from the 6 or 9 high voltage batteries.
Are the SOC values with 5% of each other highest to lowest?

Step Action

Decision

DIAGNOSTIC:

4

No. Open a technical service case file and
share the battery health report on the
case.

Yes. No change is needed.

Review the battery pack SOC values.
Average the battery pack SOC values (sum of all values, then divide by the
count of numbers that were added).
Round to the nearest whole number and record the value.
Next review the "Display SOC%" value.

No. Continue to step 5.

Is the average battery pack SOC value within 10% of the "Display SOC%" value?

Step Action
DIAGNOSTIC:
5

Review the average battery pack SOC
value.
Please select from the following:

Decision
0-19% SOC. Open a case file and share the battery health report on the case.
20-55% SOC. Continue to step 6.
56-70% SOC. Drive or Charge the vehicle to achieve a SOC value of 20-55% or
71-100%.
71-100% SOC. Continue to step 6.

Step Action
DIAGNOSTIC:
Change the State of Charge values in the BMS. See instructions below. (Link to
Repair Steps)
6

Decision
SOC was at or below 55%. Charge to
100%, restart at step 1 to confirm the
readings.

It is recommended to confirm the battery pack average SOC value compared to the
SOC was at or above 56%.
"Display SOC%" when at both the lower range, 20-55%, and again at the upper
Drive/discharge to achieve approximately
range, 90-100%.
40%, restart at step 1 to confirm the
readings.
Please select from the following:

WARMING THE HIGH VOLTAGE BATTERIES
If the high voltage batteries are below 50*F then it will be difficult to have confidence in evaluating the readings or having confidence after a change
is made. There are three ways to warm up the batteries.
If the batteries are at a high state of charge it is recommended to drive the vehicle for the purpose of warming the batteries.
If the batteries are at a lower state of charge it is recommended to charge the vehicle for the purpose of warming the batteries. Note that
charging with a level 2 (AC) charger is preferred in this case as the slower charge rate will give the batteries more time to warm up.
Parking indoors overnight is another option as the batteries will warm naturally.
When driving or charging is completed it is recommended to park indoors if possible to avoid losing the increased temperature of the high voltage
batteries.
(Return to Diagnostics step 1)

REPAIR STEPS
SDS BMS state of charge parameter change instructions

1) Open SDS and connect to the vehicle. No need for a health report at this time.
2) On the left side menu select VCU Programming.
Figure 2 - Select VCU Programming

3) Select VCU and BMS Programming
Figure 3 - Select VCU and BMS
Programming

4)Expand BMS Programming
Figure 4 - Expand BMS Programming

5) Edit Display SOC, Maximum SOC, and Minimum SOC to the average battery pack SOC value identified in step 4.
In the example below a parameter that has not been edited yet will be white in color and once edited will be shaded light purple in color. Set all
three values to the same number as you identified in step 4.
Figure 5 - Edit Values

6) Then select the Program button at the top of the screen to program in the new values. Follow the onscreen prompts to complete the
programming.

Figure 6 - Program Values

7) Return to Diagnostics step 6. (Link to Diagnostics step 6)

OTHER RESOURCES
SDS user guide. 4328790
EV resource center. RC0900002
SRT homepage Link
Master Service Information Link
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