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).
Technical memo responding to a query about potential damage from leaving an ignition switch on for 36 hours.
| Identifier | ExFiles\Box 46\3\ Scan170 | |
| Date | 11th July 1923 | |
| X.37/6 To D/BP. from EFC. EFC2/T11.7.23. c. EP.{G. Eric Platford - Chief Quality Engineer} CHASSIS 46-ZG, MRS. GROSLAND. --------------------------------- Answering your D/BP12/CW10.7.23, it is improbable that damage has been done to the ballast resistance on this car through the ignition switch having been left on for 36 hours. The ballast resistance is designed to stand this and a good deal more, and if the battery was, as we understand from the telegram, put on recharge almost immediately, very little permanent damage will have been done, but the battery life might have been reduced a trifle. As stated in the Instruction Book, the function of this resistance is to limit the current taken by the coil at slow speeds, or if the ignition switch should be accidentally left on. It perhaps should be pointed out to the customer that the ballast resistance does not switch off the current, but only reduces it to a relatively low value, so that the leaving on of the switch for a moderate period only is not a serious matter. We do not pretend that the ballast resistance would be capable of preventing the running down of the battery if left on for such a long period as stated. There are, it is true, on the market a number of devices which will automatically switch off the ignition current, but from our experience with such, we do not recommend the addition of such a device, as they can never be of an absolutely reliable nature and in practice it would be found that balancing the unreliability, against a greater tendency to carelessness on the part of the owner with such a device fitted, no advantage would be gained in the long run. The number of complaints received on the score of the ignition switch having been left on is so small that the complication of an additional device, even if it could be perfectly reliable, would not be justified. As regards the query for advice as to what should be done concerning the battery, this should be charged at half normal charging rate (i.e. half 8 amps. = 4 amps.) for a period of at least 28 hours, i.e. giving the battery at least twice its rated capacity, but in any case until the battery gases freely and the densities have returned to between 1270 and 1290. If, after continued charging, the densities were not returned to this figure, it is important to remove some of the electrolyte and replace | ||