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).
Technical memo discussing car battery under-charging, dynamo charging rates, and historical changes in battery technology.
| Identifier | ExFiles\Box 164\3\ img079 | |
| Date | 2nd December 1937 | |
| H.E.West, Esq., -2- 2nd. December, 1937. The reason that brought the battery to an untimely end was under-chaging. A hard film had got on to the plates which the charging rate of the car dynamo would never have been capable of dispersing and only special laboratory treatment could nurse it back into good health. So good were the plates that the battery has been re-assembled and is being put back on the car. New separators have been fitted because although they were quite good we did not wish them to fail as we want the plates to fail first because of finding out the relative life of the thick and thin plates etc. As to this point therefore, we must wait a further interval of time. The car is not used in a manner which should cause very much drain on the battery without charging. It has fairly normal ordinary use, if anything, perhaps a little more favourable to battery charging than the average, certainly far more favourable than say the 25/30 Rolls-Royce. We were rather disturbed at finding such a case on such a car and we have been making enquiries in many directions as to present day charging rates and as a result of these, we are going to say the standard rate is too low. In the old days on a 20 H.P. car - the early 25's. the dynamos charged at up to 10 amps. or more, admittedly falling back to about 7, but on long runs like going across France there was anything from 5 to 8 amps. going into the battery all the time. We gave continuous representations about this over the years and reported that whenever a battery failed it was due to over-charging, but in spite of all this we got very good battery life, four years and more being quite common and an average certainly of three years. When the voltage control came in, everybody hailed it as a cure for this and battery life was going to be longer and less topping up required, and batteries could be a bit smaller because the dynamo would follow the load etc.etc. On the whole, we are not getting this hoped for long life. Of course the battery size has been cut down which does not help and the demands on it have gone up, but at least carbatteries ought to last as long. When we say this, we mean on all cars not only Rolls Royce but others where voltage control has been standardised, but they do not. | ||