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Hybrid Vehicle Battery Repair Webinar

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Hybrid vehicle battery repair

The 3-hour nickel metal hydride (NiMH) hybrid battery webinar demonstrates split current charge-discharge cycling, internal resistance measurements and hybrid battery cell balancing. No prior knowledge of hybrid batteries is required.  

Hybrid battery webinar schedule (2020):

Upcoming webinar date:
July 10, 2020

Start time:
10 AM Eastern

Click here to register for this free webinar!


Webinar benefits

  • Experienced instructors provide in-depth knowledge on hybrid battery cycling, reconditioning and safety issues.
  • Learn to identify bad modules prior to reconditioning.
  • The dangers of over-charging and over-discharging.

Videos from past Hybrid Battery Webinar (May 2, 2020)

Part 1: Introduction to hybrid batteries and reconditioning

Part 2: NiMH Battery Reconditioning

Part 3: Using the EVc hybrid battery reconditioner
Part 4: Battery pack selection and assembly
Part 5: Using EVd power tester
Q&A with Prof. Eugene S. Smotkin


Background

Hybrid battery packs have 28 to 40 NiMH modules assembled in series. A Prius type prismatic module consists of six individual NiMH cells (1.2 V each) assembled in series. Detailed specifications for these modules are available.  

7.2 V hybrid battery prismatic module with individual cell marked 1 – 6


28 prismatic modules with a series nominal voltage of 202 V

NiMH modules are configured in series for high voltage hybrid vehicle battery packs. These packs undergo shallow depth-of-discharge (about 10%): They are for power assist, not electric drive.  Unused electrode material undergoes structural changes that effectively reduces amp hour (Ah) capacity. This reversible failure mode (“memory effect”)  takes modules out-of-balance with neighboring modules, especially those that are near the center of the pack. Out-of-balance modules undergo cell voltage reversal during discharge. Voltage reversal can permanently damage a module.  High-rate charging generates gaseous oxygen at the positive nickel oxyhydroxide electrode that can pressurize and rupture the module.   Modules, reconditioned by a series of deep charge-discharge cycles with tapered currents, will recover lost capacity and have extended lifetime.  Hybrid vehicle batteries that have overheated may have vented electrolyte water. This permanent failure mode increases the module internal resistance. Such  modules substantially increase reconditioning time. Modules suffering from permanent failure modes are identified and removed before full reconditioning.   

 "Out of balance" Ford Escape battery pack
Ford Escape “out-of-balance” battery pack

 Ford Escape reconditioned battery pack
Ford Escape reconditioned battery pack

Battery-sorting software module
Battery-sorting software module


Webinar Syllabus

Part I: Terminology, definitions and usage

a) Coulombs, amps, voltage, amp-hour, watt-hour
b) Cells, modules, packs, cylindrical versus prismatic cells
c) NiMH batteries vs. Li-ion batteries

Part II: Introduction to battery reconditioning (or repair)

a) Reversible and irreversible capacity losses
b) NiMH memory effect – effect of shallow depth of discharge
c) Use of state-of-health data for module sorting and battery pack assembly
d.) Refurbishing packs vs Reconditioning modules

Part III: Tools required for battery reconditioning

a) EVc-30 overview
b) Prius modules, clamping, cooling box and connections to EVC-30
c) NuVant reconditioning plans
e) Before and after reconditioning discharge profiles
f) Dangers of reconditioning – Module swelling, overheating, explosions
g) EVd-40 Power Tester

Part IV: Interpreting EVc-30 data output 

a) Results –Diagnostic discharge profile, Exporting summary files
b) QR code reader – Tracking inventory
c) Module pairing after reconditioning (Battery pack balancing)

Part V: Interpreting EVd-40 data output

a)  Searching for weak modules before and after reconditioning.