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).
Battery cell charging issues, focusing on negative plates, overcharging, and maintaining potential difference.
| Identifier | WestWitteringFiles\N\July1925-September1925\ Scan262 | |
| Date | 15th September 1925 | |
| Contd. -3- 15.9.25. If in any cell on charge the negatives do not gas as easily as soon as the positives, our experience indicates that at some time the battery has been wrongly treated in respect of one or the other of the three items above. With cells in this condition the tendency is rightly or wrongly to go on charging until the mechanical strength of the positive plates is being spoilt by over-charging which is unnecessary electrically (for the positives). Therefore from the negative elements point of view it is most important (1) To maintain the level (2) To give freshening charges (3) Never to allow the P.D. to fall below 1.8 volts per cell. It is our definite experience that cells which inadvertently have been subject to these, and particularly to the third, are not again the same in respect of their negative elements. Many have been the times when one cannot decide whether to continue charging in attempt to get the negative plates up, or to stop charging to save the overcharging of the positive plates, but this question does not arise in a battery which has been properly treated. A set of negative plates removed from a battery may look good mechanically and yet be bad electrically. A set of positive plates may look very bad mechanically and yet be good electrically. We have had very definite experience of cells of small capacity which, owing to the fault of leaky containers and otherwise incorrect insulation, have not been allowed normally to maintain their P.D., in spite of correct level and charging. Invariably it has been the case that the negative elements have been wrong, and the positives not wrong. This is proved by interchanging elements or by Cadmium Electrode (see below). Once the negative elements have been allowed so to fail, it has been impossible, by any amount of charging, to restore them to their correct condition in which the cell P.D's will keep up normally. In other similar cells which have not been subject to these leak faults, there has been no difficulty in maintaining the potentials with the ordinary amount of charging. Contd. | ||