Post on 26-Jul-2015
transcript
Spectro™ Battery Rapid-tester
What is CCA?
CCA is responsible for power delivery
What is Ah (RC)?
Capacity is energy storage, the leading health indicator
Definitions of a Starter Battery
CCA: 30s load at rated CCA at -18C (0F) Battery must stay above 7.2V to pass Ah: Discharge to 10.5V at 0.05C (20h)RC: 25A discharge to 10.5V (in minutes)
Capacity loss
Most battery testers measure CCA only.
CCA stays high while the capacity drops. This makes impedance testers ineffective.
Capacity is the leading health indicator, but this value is difficult to estimate.
Many battery testers claim to measure capacity. This is not possible with a basic impedance measurement.
Testing Starter Batteries
CCA value relates to internal resistance
Capacity and CCA of aging Starter Batteries
CCA stays high to the end; engine cranks well Capacity below 40% is considered end-of-life
Relationship between Capacity and CCA
175 starter batteries tested according to SAE J537
Few touch the 50% CCA line
Most batteries hug the 40% capacity line
Capacity determines the end-of-battery life. CCA not conclusive
Spectro CA-12
Measures Capacity of Lead Acid
Device scans battery with 20-2000Hz
Uses multi-model electrochemical impedance spectroscopy (Spectro™)
Estimates capacity in 15 seconds
Provides higher CCA accuracy than with single-frequency AC methods
15-second test
No comparable product on marketUS patent 6,778,913
Spectro is based on Frequency Domain using electrochemical impedance spectroscopy (EIS).
A frequency scan creates a Nyquist plot.
Nyquist plot
How does Spectro™ work?
Randle’s Electrochemical Model
Cadex took EIS and developed multi-model electro-chemical impedance spectroscopy, or Spectro™
Spectro™ combines EIS with complex modeling to estimate battery capacity and improve CCA results
Taking EIS Further
“All models are wrong, but some are useful”
George Box, 1919-2013
Spectro™ Progression
Signal control anddata acquisition
Filtering, phase andmagnitude extraction
Modeling, statistical analysisFitting Nyquist plots of electrochemical models to the measured Nyquist plot
Data fusionCorrelating values of key parameters to derive at capacity, CCA estimations
1
2
3
4
V= Vocos(2pft)I= Iocos(2pft + q)V= Vocos(2pft)
Generating Nyquist PlotIm
ag
ina
ry Im
pe
dan
ce
Real Impedance
Spectro™ scans the battery with 22 frequencies, generates Nyquist Plot and fits electrochemical models
Fitting Electrochemical Models
Electrochemical models evaluate R1, R2 and C of the Randle Model.
C decreases, R2 increases and the Nyquist radius flattens with age.
Randle Model
Real Impedance
Imag
inar
y Im
peda
nce
Test conditions
Battery must be at least 60% charged. “Charge and Retest” message if below 60%
Specific Matrix gives capacity in % (accuracy +/-15%)
Generic Solution passes or fails battery on a 40% capacity threshold (accuracy +/-20%)
Accuracy is based on symptoms
Low charge and faded capacity appear similar
Low formation, long storage, surface charge falsify results
What is a Matrix?
A matrix can be compared to letter or facial recognition. Samples are needed against which results are compared.
A matrix is developed by scanning many good, marginal and poor batteries.
Most service personnel use the generic matrix.
The pass/fail provides conclusive test results.
Battery-specific matrix reads the capacity in %
Generic Matrix gives a pass/fail a 40% threshold
CCA test with CA-12: 97%
CCA test with competitor: 51%
According to independent
test lab
13%
87%
Correct Incorrect
Capacity test with CA-12: 87%
Capacity test with competitor: N/A
97%
3%
Correct Incorrect
Correct prediction with Specific Matrix
CCA Capacity
AGM 70-90 Ahr
Correct prediction with Generic MatrixCapacity only
Flooded 70-90 Ahr
Batteries were charged and discharged according to EN-Norms. Results were compared with Spectro CA-12
CCA accuracy +/-5%;Capacity accuracy +/-20%
General service garages Warranty at dealership Fleet vehicles
Markets for Car and Truck Dealerships
Battery health in boats, aircraft and heavy equipment are best verified with a capacity check.
Markets for off-road Vehicles
Capacity is the leading indicator when to replace a battery. Capacity also governs the hotel load.
Markets for diverse Vehicles
Markets for Deep-cycle and UPS Batteries
Spectro CA-12 estimates capacity without discharge. Enables more frequent battery check.
Limitations: - Provides SoC only- Cannot estimate capacity- Loses accuracy as battery ages
Sensor reads voltage, current, temperature
Battery Monitoring - what is used today
Adding capacity to BMS ─ On Drawing Board ─
Adding capacity advances a battery sensor to an advanced BMS providing State-of-Function (SoF)
SoF in a Tri-state Fuel Gauge
Tri-state Fuel Gauge shows Usable capacity Empty portion Unusable capacity
Conceptual
─ On Drawing Board ─
Markets