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).
Rejecting a battery indicator from J.H. Wedge & Co. in favour of an alternative green lamp system.
| Identifier | ExFiles\Box 54\2\ Scan225 | |
| Date | 24th May 1928 | |
| To Roy. {Sir Henry Royce} from EFC. {E. Fowler Clarke - Electrical Engineer} X4457 EFC {E. Fowler Clarke - Electrical Engineer} 3/T24.5.28. BATTERY INDICATOR FROM J.H. WEDGE & CO. We have duly read their letter of May 11.th which we now return. This instrument is only a moving coil voltmeter with a scale divided into coloured divisions corresponding to certain voltage figures, and therefore there is no difficulty in knowing the value of the type of indications that it will give. It is a correctly recognised thing that voltmeter indications of a battery are not accurate indications of the capacity available from that battery. In regard to giving the information as to when to switch off, this feature of the instrument would be more useful. We say, however, that it requires two units of human element, one to observe the instrument and the other to operate the switch. You may know that we have on test a green lamp scheme whereby a green lamp is lighted when the voltage rises to an appropriate figure, and therefore does not call upon the driver to make a special observation, as he cannot miss the appearance of the light whatever he may be thinking about. Then he must switch off by hand - one unit of human element. Because we consider this arrangement better than the voltmeter method, we are not interested in this method. EFC. {E. Fowler Clarke - Electrical Engineer} | ||