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).
Report page discussing ignition ballast resistance characteristics and observations on battery charging E.M.F.
| Identifier | ExFiles\Box 61\2\ scan0224 | |
| Date | 16th June 1926 | |
| EFC3/T16.6.26. -3- Contd. resistance of the same characteristics as ignition ballast resistance is more suitable than a resistance of the invariable type, in that whereas the latter allows the reduced output curve to fall and become still further reduced at the higher speeds, the former type has the effect of flattening the reduced curve in such a way that the smaller output is maintained at the higher speeds instead of being reduced to what might be considered too small a value, and we judge this to be an advantage. This matter again may constitute the subject of a separate report. The other is with reference to battery charging E.M.F's. We shall have a report to make on some observations of the true E.M.F's of batteries whilst on charge, these being obtained by a null balancing method by instantaneously switching over from a charging current at various given rates to an instrument connected to an auxiliary battery and potentiometer adjusted nearly to the E.M.F. to be observed. In this way we can get a very quick reading before the E.M.F. of the battery as sustained by the charge has had time to sink appreciably. These results are rather an eye-opener because they shew - (1) That it is possible for a standard 12 volt battery charging at full normal charging rate actually to put up a true back E.M.F. of 17.0 volts or thereabouts. (2) That the ohmic resistance of the battery as estimated from the difference of P.D. when on charge and true Contd. | ||