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).
Explaining the function and testing of Battery Capacity Ampere Hour Meters and Accumulator Capacity Indicators.
| Identifier | ExFiles\Box 54\2\ Scan227 | |
| Date | 24th May 1928 guessed | |
| X.4457 BATTERY CAPACITY AMPERE HOUR METERS & ACCUMULATOR CAPACITY INDICATORS. These Instruments can be supplied to suit any number of cells and in various patterns, and are a specially designed Voltmeter which enables us to obtain approximately a one inch scale length between the maximum or fully charged voltage and the safe minimum voltage of a Battery respectively. This is considerably greater than the length of the corresponding part of the scale of an ordinary Voltmeter. The comparatively great area permits of the scale being calibrated so that accurate readings can be taken when a load equivalent to a 10 or 20 hour continuous discharge is put across the Battery. We are sure you will agree that the main characteristic of a Battery is voltage, and as the voltage deteriorates so does the amperage proportionately. Voltage taken on open circuit is unreliable and very misleading, whilst voltage on a closed circuit of a 10 hour rate discharge indicated over a scale area between the maximum or fully charged voltage and the safe minimum voltage of a Battery respectively is the only reliable way of obtaining an indication of the state of charge. When testing these Instruments for accuracy it is necessary that a new Battery which has been charged to the Makers instructions be used, then charge the Battery at various periods of time and rates of charge, allow a period of 2-3 hours after charging has ceased for the Battery to settle and the voltage to become constant, then connect the Instrument together with a 10 hour rate load shunt across the Battery, observe the Ampere Hours indicated and compare with the length of time taken to discharge the Battery to the Red Indication mark on low portion of scale which is the safe minimum discharge voltage indication. When these Instruments are fitted to Motor Cars it is not necessary to have a separate load shunt for test purposes as the load of the lamps are approximately equivalent to a 10 hour discharge rate. Special 2 volt testers can be supplied with various load shunts suitable for testing any size Battery whatever its condition may be. | ||