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).
Investigations into the operating qualities of the 'green lamp scheme' and variations in battery voltage due to temperature changes.
| Identifier | WestWitteringFiles\T\2January1929-June1929\ Scan227 | |
| Date | 8th May 1929 | |
| To R.{Sir Henry Royce} from EFC. c. SG.{Arthur F. Sidgreaves - MD} R.{Sir Henry Royce} c. HY.{Tom Haldenby - Plant Engineer} Nor. ORIGINAL EFC5/T8.5.29. GREEN LAMP SCHEME. X4040 X7780 Since writing our report EFC2/T1.2.29, in which reference was made to the operating qualities of the green lamp scheme, we have continued more exact investigations and observations on the variation of operating voltage of the electrical system in various circumstances, on which the functioning of the green lamp switch would depend. Perhaps the outstanding feature which is rendered evident is the fact that the P.D. of the same battery in the same state of charge varies considerably with the mean temperature of the battery, which mean temperature can in its turn, especially with batteries in the rear of frame position, be subject to considerable variation, more particularly as a result of being situated in a current of air which has largely passed through the bonnet of the car. As an instance of this, one particular pair of observations is to the effect that the maximum P.D. of a fully charged battery charging at peak rate on a car reached a figure of 17.0 some while after starting, but subsequently dropped actually as far as 16.2 volts with the same charging current still flowing. The effect appears to be entirely due to rise of temperature of the electrolyte. On the one or two green lamp schemes which we have running on experimental cars, we had in the early stages been a little puzzled because in spite of our careful setting | ||