November 03 2017
RICHMOND, BC, Canada (November 2017). In early 2017, Discover introduced its range of MIXTECH EGM batteries. Included in this range were the following BCI group 31 models:
- EGM1000-31 750CCA/190RC
- EGM1050-31 800CCA/200RC
- EGM1150-31 850CCA/210RC
During our ongoing life cycle and performance verification testing, we became aware of a discrepancy between our published performance capacities and tested and verified capacities. After completing an internal review of this discrepancy and how it happened, we determined that we published capacities for the batteries without taking into account the increase in Internal Resistance (IR) caused by the additional Glass Mat separator. EGM battery models use two glass fiber embedded separators, 1) Fiber-lock scrim separators on both the positive and negative plates, and 2) an additional Glass Mat separator combined with the PE envelope separator on the positive plate.
Separators are used between the positive and negative plates to prevent short-circuit from physical contact and from active material shedding. Separators also obstruct the flow of ions between the plates and increase the battery's internal resistance. So, while adding the second Glass Mat separator greatly enhances the batteries life by increasing cyclic stability and vibration resistance, it also increases the battery's IR.
An effective battery separator must possess a number of mechanical properties such as porosity, pore size distribution, mechanical design and strength, electrical resistance and conductivity, and chemical compatibility with the electrolyte. The area of the separator must be a little larger than the area of the plates to prevent material shorting between the plates and the separators must remain stable over the battery’s designed operating temperature range.
The inherent electrical resistance of the battery's separators is a measure of the difficulty to pass an electrical current through the separator and manifests itself in voltage (V) drops or a drop-in pressure or ability to move the current in amps (A) through the battery (the higher the IR the greater the V drop). The result of this increased voltage drop (in pressure) is lower potential for continuous cranking amps or reserve capacity amps in a battery with an extra separator than the exact same battery without the extra separator.
For CCA, higher IR impacts the batteries ability to maintain its designed cranking performance above 7.2V for at least 30 seconds and for RC, IR impacts the length of time a battery can sustain a 25A draw while maintaining a voltage above 10.5V. Our testing shows that:
Existing Model / Published / Verified
- EGM1150-31 Published: 115AH/850CCA/210RC
- EGM1150-31 Verified with PE+GM: AH over published by an average of 9%-11%
- EGM1150-31 Verified with PE+GM: CCA over published by an average of 15%-20%
- EGM1150-31 Verified with PE+GM: RC over published by an average of 9%-11%%
In addition to eliminating acid stratification with MIXTECH technology, the key performance features identified by the product development team for the EGM range were:
- Vibration Resistance for increased durability
- High Cycle Capability for house load support
- Improved corrosion resistance for high heat use
- Improved charge acceptance for improved durability in Start-Stop vehicles or when used with high output alternators.
The second Glass Mat separator, although not an absolute requirement to meet our design objectives, was added to further improve cell compression, cyclic durability and vibration resistance.
Key customers and the development team determined that we needed to maintain a higher CCA option as well as the option that included the extra cyclic and vibration durability provided by the extra separator. Therefore, we are making the following changes to the current MIXTECH EGM product range:
1. Key models in the commercial EGM product range will be made available with and without the extra Glass Mat separators (similar to other producers of OEM batteries for commercial applications. See competitor’s listing below). All models, regardless of whether or not they have the extra separator, will be produced using the fiber-lock Glass Mat scrim.
2. Affective immediately, the Group 31 EGM models will be reduced from three to two models. One with and one without the additional separator.
a. EGM1150-31S (31A) 115AH/850CCA/210RC
b. EGM1020-31S (31A) 102AH/730CCA/180RC
We sincerely apologize for the inconveniences caused by our oversight. We look forward to continuing to expand our MIXTECH EGM product range to meet you demand for solutions to battery challenges in the commercial and Start-Stop vehicle segment. Watch for BCI 4D and 8D, JIS N120, 150 & 200 and DIN A,B,C models to be released in 2018.