Battery repair equipment & theory
Hybrid vehicle battery reconditioning, repair and maintenance equipment for individual | fleet servicing
What is an HEV battery module?
Modules are nickel metal hydride (NiMH) cells connected in series. NiMH cells are typically rated at a nominal voltage of 1.2 V. A Ford Escape module has 5 cylindrical NiMH cells in series. A Toyota Prius module has 6 prismatic NiMH cells. The full traction pack battery consists of many modules configured in series. A Ford Escape has two 25-module traction packs. A Prius has a single 28-module pack.
|cells/module||module V||type||modules/pack||pack V|
|Ford Escape||5||6||cylinder||25||150 V|
What does “out of balance” mean?
The driving cycle of HEV battery modules only a shallow depth of discharge that uses no more than 10% of the battery capacity. Chronically unused capacity becomes separated and essentially unavailable with time. This reversible failure mode (i.e., module-to-module variation of amp-hour (Ah) capacity) results in an “out of balance” battery pack. This is often referred to as the “memory effect”.
What is battery cell balancing?
Balancing is module reconditioning (to recover capacity) followed by sorting and positioning of modules for optimum performance. The steps are:
1 Extraction of the battery pack from the pack enclosure
2 Removal of high voltage cable
3 Parallel connection of modules to a charge discharge system,
4 Rapid identification and switch-out high resistance modules (e.g., > 10 mΩ for a 6-cell module)
5 Split-current cycling at deep depths of discharge
6 Sorting modules based on watt hour capacity
7 Properly positioning modules into a full pack
What tools are needed for battery reconditioning and pack assembly?
The tools to build a high-growth, sustainable business of reconditioning and pack assembly are (1) a sophisticated charge discharge tool and (2) a database to store amp-hour capacity and midpoint voltage data on every single module maintained in inventory. That database can wait while you build your business. Sooner or later, you will need a database. In summary:
Charge/discharge tool: EVc-30
Includes instrument, training and EVcharge software.
An enhanced version of EVcharge that includes the database. EVcharge-plus imports module analysis data from the EVc-30. The database tracks modules and sorts for assembly of battery packs. Advanced sorting routines filter out bad modules for pack assembly based on end-user set parameters. Track installation of modules to vehicles using VIN number, customer ID or 3rd party shop identity. Inventory is segregated based on module format (e.g., prismatic, cylindrical, etc.).
How long does it take to recondition a hybrid battery pack?
Cell balancing can take 12 to 72 hours depending on your choice of the end of discharge voltage (VEOD). NiMH modules have system parameters specific to the form factor (e.g., prismatic versus cylindrical) and number of cells in series (e.g., Ford Escape: 5; Prius prismatic: 6; etc.). These parameters are the VEOD and the reset current (IRESET). For the Prius pack, the historical value VEOD is 6 V. IRESET is the highest current possible to reset (discharge) to VEOD with a relaxation (i.e. bounceback) of less than 3%. Resetting is step-one in a CBP. While NuVant is establishing IRESET, a reasonable value for now is 100 mA. Using an IRESET(100mA) results in a CBP exceeding 40 hrs. This can be shortened by increasing VEOD, for example to 6.8 V. However, the higher the VEOD, the lower the quality of the CBP. A “family” vehicle with less than two years of lifetime may benefit from a shorter CBP for lower warrant costs. CBP protocols and their automated implementation are covered in the NuVant battery reconditioning course. The business model is not extract-balance-reinstall on a per customer basis, but rather development of an inventory of characterized modules for instant replacement of customer packs. This requires a variety of VEOD values depending on warranty options.
What battery conditioning data does the EVc provide?
The EVc gives internal resistance, amp-hour, watt-hour capacity and real-world nominal voltages for every module. The separate PackBuilder package uses this data to rank modules for pack rebuilding. EVc output files are shown below for some popular traction battery packs.
Toyota Highlander (click on figures to expand)
Ford Escape (click on figures to expand)
Toyota Prius (click on figure to expand)
Battery-sorting software provided by the EVcharge package. The sorting is limited to the pack just reconditioned by the EVc-30. Sorting can be applied to your entire inventory using EVcharge-plus.
The EV database analyzes the above data and suggests modules from your QR coded inventory for assembly of packs. Addition information concerning the PackBuilder will be provided in the short courses.
How do I learn more about battery repair prior to purchasing an EVc?
The hands-on hybrid electric vehicle battery reconditioning short course allows participants to connect Prius pack modules to an EVc reconditioning unit for cell balancing. During the reconditioning process, the terminology required for understanding cell balancing will be thoroughly explained. On the second day, results of the overnight process are thoroughly discussed along with data processing by the PackBuilding analysis package.
Testimonials from existing EVc users
|Max Load Voltage||10 V/channel (Customized up to 20V)|
|Max Load Current||5A per channel|
|Number of channels||10, 30 or 40 channel systems|
|Applied Current Accuracy||0.5% of the Applied Current|
|Applied Current Resolution||.3 mA|
|Measured DC Potential Ranges||10 V/channel (Customized up to 20V)|
|Accuracy||0.08 or 0.03% of FSR|
|Current Interrupt Resistance|
|Data Acquisition Speed||12.5 kS/s|
|Serial Resistance Precision||0.5 %|
|Measurement logging time||1 second|
What if I need additional training after an EVc purchase?
New owners of EVc reconditioning equipment receive a complementary 5-hour EZtime ticket. This complementary on-line (TeamViewer) training provides sufficient time for remote reconditioning of your first 2 packs simultaneous with the suggested training agenda.
- On-line training provided after customer receives purchased EVc unit. Training includes:
- Unpacking and set-up of EVc unit.
- Connections to prismatic or cylindrical modules
- Use of EVc to identify high resistance modules
- Module reconditioning
- Database module sort and pack build-up.
- Additional 5-hour EZtime tickets can be purchased for $175.
Call 219-644-3231 for more details