From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Defining the standard resistance and limits for high-rate discharge tests on batteries.
| Identifier | ExFiles\Box 61b\3\ scan0143 | |
| Date | 1st September 1921 | |
| X543 d6027 EFC/TS.9.21. X.664 - HIGH RATE DISCHARGE TESTS OF BATTERIES. X543 The invariable resistance through which future battery high rate discharge tests are to be taken will now be .100 ohm, so that 100 amperes will correspond to 10 terminal volts, i.e. a drop of two volts from the standard open circuit voltage figure 12.0. We assume the battery E.M.F. virtually to remain at 12.0, so that when the battery is discharged at A amperes through this resistance, the total circuit resistance is 12/A and the virtual battery resistance is 12/A - .1. Thus the virtual battery resistance when discharging 110 amperes is .009 ohm. When discharging 104 amperes is .015 ohm. and when " 100 " " .020 ohm. The figure we have suggested for our limit for virtual battery resistance is .015 ohm, hence if a battery is not in a condition in which it can discharge more than 100 amperes through the standard resistance of .10 ohm. it is quite unsuitable for operating a motor, with a characteristic up to our standard. Thus the value of the battery from this point of view is measured by the frequency of circumstances in which it is capable of discharging a greater current than 100 amperes through this .10 ohm. EFC, | ||