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).
Letter to The British Sangamo Co. Ltd. discussing the suitability of their ampere-hour meter for experimental battery charging.
| Identifier | ExFiles\Box 164\3\ img221 | |
| Date | 15th September 1938 | |
| Battery 6021. EXPERIMENTAL DEPARTMENT. Rm {William Robotham - Chief Engineer} /RC. {R. Childs} 14/JH. 15th September, 1938. The British Sangamo Co.Ltd., Cambridge Arterial Road, Enfield, Middlesex, Dear Sirs, We thank you for your letter reference T.4310.HS {Lord Ernest Hives - Chair} /JW/4, and the attached leaflets. After reading the matter in connection with your N.F. type ampere-hour meter, we are not clear as to whether this instrument embodies a time switch. If so then we should not require a separate time switch. Also it appears that the instrument you offer is unnecessarily complicated, for our purpose. To explain briefly, we have a number of small batteries of a nominal capacity not exceeding 65 ampere hours each (at the 10 hour rate). These batteries are being treated experimentally on the bench during which they are discharged during the day, and must be charged during the night, connection in series from 100 volt D.C. supply mains. The conditions of test are such that a definite charge input of 63 ampere-hours must be given to the batteries. Since the charging current is 7.0 amperes, this means charging for 9.0 hours, and all we require is an instrument that will accurately measure this quantity and switch off at the correct time. The charge input of 63 ampere-hours includes a definite amount of additional charge, therefore we should not need the over-charge device. Actually the batteries would be connected up in the evening in series with a suitable control resistance, and ammeter and the circuit closed by hand, using an ordinary switch at a certain hour. It would be the job of the ampere hour meter to merely measure the input quantity and switch off at the required hour. | ||