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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 discussion on vehicle battery charging, starter consumption, and the proposal for automatic dynamo control.

Identifier  ExFiles\Box 165\6\  img238
Date  14th December 1923
  
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Further, lamp consumption and particularly starter consumption is not reduced proportionally and the rate of loss of charge of the battery is accelerated. Particularly is this the case in the starter motor case as it is certain that when the battery becomes low for high rate discharges, more of the battery capacity will be used on the starter, as a result of less effective starting. A battery is often "rundown" from a starter point of view when apparently quite normal on side or dash lighting even for a considerable time. The test is, how much drop of light intensity occurs when the starter button is pressed, and from this it can be judged as to whether it is time to give the battery a garage charge.

For the above reasons it appears almost inevitable in every case that either overcharging or undercharging will result and that in a great many cases garage charging becomes a necessity in winter time, if overcharging troubles are to be avoided at other times.

In our own opinion the only solution is external control of an entirely automatic nature. This would permit the possible output of the dynamo when required to be higher than at present. We have had in the past one or two instances of satisfactory automatic control on experimental cars.

In regard to the actual position in respect of dynamos and particularly that of "Intermediate Output" dynamos further to out EFC3/AD28.11.29, we now send attached two blue prints one referring to 20 HP. and one to Phantom II.
  
  


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