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).
Analysis of using voltmeter readings to determine the state of a battery's charge.
| Identifier | WestWitteringFiles\P\2July1926-September1926\ Scan082 | |
| Date | 21th August 1926 | |
| Contd. -2- Under steady conditionse of charging the battery, i.e. at constant current at normal rate, its terminal P.D. would gradually rise to an ultimate figure in the neighbourhood of 17.0, and the indication of the voltmeter on the system might at such times reach or nearly reach 18.0. Actually the charging current to the battery is varying considerably according to the speed of the dynamo, so that this voltage would be fluctuating from time to time and cannot therefore be used as a steady indication of the state of the battery. It would be possible to instruct that the charging current should be switched off when the voltage indicated by the instrument exceeds a certain amount. In passing it might be mentioned that a limited scale voltmeter, 10.0 to 18.0 volts, would be more useful than one reading all the way to 18.0 volts, because its indications would be on a more open scale. The question arises as to what the amount should be at which the charge should be switched off. If the amount fixed upon is a comparatively low figure, say 15.5 volts, or even 16.0 volts, it is by no means certain at present that the battery will be effectively fully charged. This matter is under investigation in connection with automatic means external to the dynamo of controlling the charging current, a satisfactory arrangement of which will be superior to hand switching following the indication of the voltmeter. Contd. | ||