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).
Battery charging curves, brush issues, and overcharging prevention.
| Identifier | ExFiles\Box 51\1\ Scan197 | |
| Date | 25th July 1923 | |
| Contd. -2- EFC {E. Fowler Clarke - Electrical Engineer} 6/T. 25/7/23. We are now, however, preparing a new curve based on our new production specification of performance, and in this new curve the ignition current has been automatically deducted by having an ignition running from the battery at the same time, the temperature at which it is taken being the same as previously, viz. 85ºC of the dynamo. This curve will be sent along to you. 3. Regarding the increase of charging current after the car leaves the Works, we have been going into this question and have found that it is largely a question of perfectly correct brush bedding in the first instance. If this is correct and the brushes and brush holders are not interfered with, the charging current does not go up. 4. You may be sure we are doing all we can to prevent any increase in charging current after the machines have been set, but as you are probably well aware, the output of machines of the 3rd brush system of control is rather sensitive to alterations in the brush bedding, particularly that of the control brush and the brush electrically adjacent to it. 5. We are glad to hear the batteries you are delivering hitherto will be able to withstand overcharging better than anything you have sent us before, and we ourselves feel that trouble on this score, for various reasons, will never be at all serious. 6. We do not specifically refer in our Instruction Book to the condition of summer running, but we have a section under 'Care of Battery' entitled "Use of Charging Switch", which is as follows :- "If the car is used in circumstances which require "frequent use of the starter and lights, it will be "found quite necessary always to keep the charging "switched on when the engine is running. "The current generated by the dynamo falls off "with increasing speed, so that the danger of over-"charging by long fast runs in the daytime is much "reduced. When, however, the battery is known to "be fully charged and the car is running at a moderate "speed only, it would generally be advisable for the "charge to be switched off. "It is important that the battery be kept fully "charged, but be not overcharged at a high rate of "current, as this may cause the temperature limit | ||