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).
The voltage characteristics and fault diagnosis during the charging of a battery cell.
| Identifier | ExFiles\Box 44\5\ Scan027 | |
| Date | 12th December 1927 guessed | |
| -4A- Contd. In the process of charging a normally good and new cell, the positive element should gradually increase from 2.05 volts positive to the cadmium before charging to 2.50 volts positive at the end of charge, whilst charging. At the same time the negative element should become less positive to the cadmium than .25 volt and, passing through the same potential as the cadmium electrode, should become negative to that electrode to the extent of about .2 volt. These figures apply to a cell in new and good condition, but in a cell which has seen some service, it may be considered reasonable to read 2.40 volts on the positive and .1 volt on the negative (i.e. negative to the cadmium). If these figures cannot be reached by prolonged charging, it is evidence, in the first year or so of the cells' life, of wrong condition either of the positive or negative elements brought about by incorrect treatment. In older cells it will often be found very difficult to make the negatives reach this point. Some portion of the weakness thus exhibited may be due to increasing age, but some may be due to premature ageing as a result of incorrect treatment of the cell at some previous time. It does not follow however that the negative plates will not gas or that the capacity of the cell is seriously reduced. Although an electrical weakness of a cell when in some intermediate condition than discharged and discharging (1.80 volts) and fully charged and charging at normal rate (about 2.60 volts) may, after some experience, be judged from the reading of the instrument (i.e. excluding broken lugs, etc.) nevertheless the principal utility of the cadmium electrode will be apparent when the cell has either reached a P.D. of 1.80 volts on discharge or of from 2.50 to 2.75 volts on charge, for then the readings are more definitely right or wrong. EFC. | ||