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).
The performance and limitations of dry cell batteries used for engine ignition.
| Identifier | WestWitteringFiles\J\January1923\ Scan5 | |
| Date | 1st January 1923 | |
| Contd. -2- EFC2/T1.1.23. The next day a short circuit current of 2.9 amperes was attained, the open circuit voltage being 1.41. Subsequently the short circuit current taken at intervals began to decrease, also the open circuit voltage. The set of 12 cells did not begin to operate the ignition until about half an hour after filling and then only caused feeble sparking to occur, the running current being considerably less than that of a normal 12 volt battery, and the average voltage during operation of the ignition only about 8. The open circuit voltage of these 10 cells after operating the ignition for a short while was 12.5. It was decided that the battery would not be of much service for starting the engine on the car, though for the sake of completeness such a test was made, which proved our expectations to be correct. We have no reason to suppose that any other make of dry cell of the same size and weight would give any better performance. There is necessarily a rather large amount of internal resistance in the cells, and since the normal running current is about 1.5 ampere at 12 volts, cells of this size would have to be used say 14 in series and 2 in parallel, which would be out of the question. The weight of the 10 cells tried, together with their wooden box, is 12 lbs. 3 ozs. We think from experiment that to attempt to start the engine from dry cells in this manner is quite out | ||