Cold-cranking

The Cannon Instmment Company produces a line of rotational viscometers, most of which are quite specialized, eg. Cold Cranking Simulators (ASTM D5293) and Mini-Rotary viscometers (ASTM D3829 and D4684) for automotive engine oils. They also have a general use instmment similar to Brookfield s basic viscometer. 

As measured in the Cold Cranking Simulator (CCS). As measured in the Mini Rotary Viscometer (MRV). 

Applying this to the above example for an area of 1 in2 = 6.45 cm2, the result is R= 8.8 mQ in2. Taking an example from SLI battery practice one cell with six positive and seven negative electrodes of typical 114 mm x 147 mm size with the above separator show a resistance of 28.3x10 6Q at 25°C, or close to 75xl0 Q at -18 °C. For a cold crank current of 320 A and six cells in series in a 12 V battery, the voltage drop due to the separator resistance amounts to w 0.15 V Fig. 5 shows this correlation. 

Figure 5. Cold crank voltage as a function of separator electrical resistance )...

During the first trials with synthetic separators around 1940 it had already been observed that some of the desired battery characteristics were affected detrimentally. The cold crank performance decreased and there was a tendency towards increased sulfation and thus shorter battery life. In extended test series, these effects could be traced back to the complete lack of wooden lignin, which had leached from the wooden veneer and interacted with the crystallization process at the negative electrode. By a dedicated addition of lignin sulfonates — so called organic expanders -— to the negative mass, not only were these disadvantages removed, but an improvement in performance was even achieved. 

Whereas a maximum number of contact points between PVC grains is desired to achieve mechanical stability, this prevents higher porosities. Typical values for porosity are 30 - 35 percent therefore the electrical resistance is rather high, i.e., 170 mQcm2, despite thin 0.3 mm backwebs for top qualities. As mentioned, the range is very wide — even considerably higher electrical resistances are sometimes acceptable, e.g., in areas where cold crank performance is of no significant importance. 

Cold crank performance, battery life expectancy, and freedom from maintenance are generally co-affected by the separators, whereas ampere-hour capacity remains largely unaffected at a given separator thickness. The properties of the different leaf and pocket separators are compared in Table 10. These typical separator properties (lines 1-4) are reflected in the electrical results of battery tests (lines 5-8). The data presented here are based on the 12 V starter battery standard DIN 43 539-02 tests based on other standards lead to similar results. 

Because of the increased shedding with these alloys, pure leaf separation is hardly suitable. Separations with supporting glass mats or fleeces as well as microfiber glass mats provide technical advantages, but are expensive and can be justified only in special cases. Also under these conditions of use the microporous polyethylene pocket offers the preferred solution [40]. Lower electrical properties at higher temperatures, especially decreased cold crank duration, are battery-related the choice of suitable alloys and expanders gains increased importance. 

Cold Cranking Simulator (CCS) An intermediate shear rate viscometer that predicts the ability of an oil to permit a satisfactory cranking speed to be developed in a cold engine. 

Low temperature performance. The cold crank simulation test is of vital interest to any car owner living in a cold climate. The advantage of a PAO-based formulation in the crankcase is immediate and obvious on a cold winter morning ... 

However, multigrade oils do not behave as Newtonian fluids and this is primarily due to the presence of polymeric viscosity index improvers. The result is that the viscosity of multigrade oils is generally higher at -18°C (0°F) than is predicted by extrapolation from 38°C (100°F) and 99°C (210°F) data, the extent of the deviation varying with the type and amount of viscosity index improver used. To overcome this, the SAE classification is based on a measured viscosity at -18°C (0°F) using a laboratory test apparatus known as a cold cranking simulator (ASTM D-2602). 

The cold crank simulator test, ASTM D2602/IP 383, measures the apparent viscosity of an oil sample at low temperatures and high shear rates, related to the cold starting characteristics of engine oils, which should be as low as possible. The oil sample fills the space between the rotor and the stator of an electric motor, and when the equipment has been cooled to the test temperature, the motor is started. The increased viscosity of the oil will reduce the speed of rotation of the motor and indicates the apparent viscosity of the oil. The test is comparative for different oil samples rather than an accurate prediction of the absolute performance of an oil in a specific engine. 

The stability of BaPbOs and its effect on the performance of a battery over its useful life have also been investigated for automotive applications [12-14]. A conventional automotive cell with 1 wt.% BaPbOs in the positive paste and a control cell were formed by means of a standard high-rate formation procedure. Cell performance was then evaluated by means of a standard Battery Council International (BCI) sequence of reserve capacity and cold-cranking tests. The cell containing BaPbOs formed three times faster with 12% less input capacity. The BCI test results of the two cells were comparable. 

Energy to battery from alternator M Battery provides energy for cold crank over life rating... 

Automotive functions that support the heat engine, such as cold crank (a 300 ms — 30 s burst of high power to start the engine) and engine controls. 

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