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 causes of battery failure, including over-charging effects, plate degradation, and separator materials.
| Identifier | ExFiles\Box 46\3\ Scan076 | |
| Date | 18th May 1922 | |
| - 4 - You will observe that I am not discrediting the fact of the good service which you so positively assert but in view of the facts I had to deal with when examining the two dismantled batteries, I can only ascribe the improved service to the points enumerated. Coming now to the actual points incorporated in Ps9/JP. 18.5.22. in dealing with the first, that is, the over discharging effects as examplified in the faulty batteries, you describe this as (a) Negative plates falling down and spongy. (b) Positive plates buckled and cracked. Our experience at Derby would have led us to have expected both of these effects as the result in the first place of over-charging. Persistent over-charging would make the negative plates spongy and tend to loosen the paste from the grid, with the result that some of the paste would be likely to fall out and build up at the bottom, eventually resulting in short-circuiting between the positive and negative plates. The buckling of the positive plate might be due either to excessive over-charging to a certain extent, and also to the effects of the short-circuiting by the paste falling out of the grids of the negative plate as described. The battery would of course finally be discharged as the result of the short-circuiting. From the numbers quoted, two of the cars with faulty batteries are "O" Series cars which should have been fitted with perforated ebonite separators in addition to the wood separators. Could you state whether any of the faulty batteries actually had ebonite separators between the plates. as our own experience has been that when failures have occured they have been almost exclusively confined to the original type of battery using wood separators only. With reference to your information and the evidence brought to bear to prove same correct, that the battery is at fault, if the cars are run under normal conditions we should agree that it is the battery rather than the dynamo, but we must still point out that with the amount of current available from the dynamo, and running persistently at night only, it is still possible to cause the battery to fail by running down, since with all the lights on and occasional use of the starter, the dynamo will not meet the full electrical requirements of the car under these extreme conditions; whilst on the other hand, if the car is run | ||