Cranking tests

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. 

The test rig aetually measures the first four items, and a eomputer ealeulates internal resistance and voltage and automatieally plots the composite curves. To produee these eurves, the brake resistance is changed from zero to the stalling torque over a period of about 10s. so the test is appropriate to short-time cranking. Tests can be elone on batteries chilled to —12. —18 or —30°C. The rig ean also be operated at a specific brake resistance to simulate the engine resistance at a specified temperature. 

Figure 18,22 Effect of separatorthickness on cold petfomiance. -18 C cold cranking test at 280A, SAE J-537 test procedure. 9-plate antirnonlal alloy cells/cellulosic separators 29 observations (Courtesyof W. R. Groce)...

Sen/ice, test and isolated position indicator Cranking screw Padlocking arrangement Tray... 

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. 

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. 

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 ... 

A new proposed SAE Viscosity Classification not only reflects lower than 0°F temperature cranking characteristics of an oil, but also covers low temperature pumpability characteristics (j), 10). Low temperature cranking success without oil pump-ability could result in oil starvation and subsequent engine damage. This new proposed classification attempts to establish a maximum cranking viscosity and then classifies oils according to what temperature they match this viscosity. It also includes a low shear test (mini-rotor viscometer) to duplicate pumpability of the oil at various low temperatures. Needless to say, minimum... 

At this point, we need to consider a very important idea. As the equation stands, we need to use the quadratic equation to solve it. You re not going to want to spend your precious time on the AP test (or even now) cranking out quadratic equations, so we re going to make an estimate. The only catch is that we always have to check to make sure that we can get away with the shortcut. The shortcut is to assume that the value for x is going to be so small that subtracting it from 0.10 won t make a dent in it. For example, pretend that x is 0.00001. Subtract that from 0.10. You get 0.09999, which is essentially 0.1. So, we re going to forget about the x in the denominator of the fraction. When we have solved for x, we ll go back and see if we can get away with it. Our new equation is ... 

Solution of the differential equations was by Gauss-Seidel iteration (with the fluid property values given in Table II) on an IBM 370 digital computer using implicit difference equations of the Crank-Nicholson type. The program was convergent and stable for all conditions tested. 

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). 

Figure 10. Different generations of the European test cycle to measure the exhaust emissions from passenger cars and light duty vehicles (c=cranking, s = sampling start).

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 dry-test meter and the wet-test gas meter are volume-measuring devices. A set of plastic bellows is alternately filled and emptied, thereby driving the dial points via a system of bell cranks very little pressure is required. A thermometer and manometer are provided with the meter, for temperature and pressure corrections. Dry-test gas meters are useful for large-volume measurements. The wet-test meter is generally more accurate that the dry-test meter for smaller volumes. The gas drives a rotor, which in turn drives the meter. The meter housing is partially filled with water through which the rotor turns. It is calibrated by the manufacturer at a given level of water. 

Finite difference methods have been used bpth to test the assumptions made in the derivation of eqn. (27) under the Leveque approximation [35] and to solve electrochemical diffusion-kinetic problems with the full parabolic profile [36-38]. The suitability of the various finite difference methods commonly encountered has been thoroughly investigated by Anderson and Moldoveanu [37], who concluded that the backward implicit (BI) method is to be preferred to either the simple explicit method [39] or the Crank-Nichol-son implicit method [40]. 

The diffusion equations described in the previous section have been derived from Pick s second law for unidirectional diffusion with the assumption that the diffusion coefficient is constant throughout the reaction. Crank [82] has also derived equations for evaluating diffusion data for systems with a variable diffusion coefficient that can be used to test one s data. 

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