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 over-charging issues and proposing an automatic volt-operated cutout as a solution.
| Identifier | ExFiles\Box 59\1\ Scan064 | |
| Date | 9th June 1926 | |
| X4008 PN{Mr Northey}13/DN9.6.26. To Hs.{Lord Ernest Hives - Chair} FROM PN{Mr Northey} c. to R, BJ, H & CWB. IGNITION. X.4617. X.8680. X.8660. X.8780. X.4008. In connection with the upkeep of batteries on our cars, statistics indicate that considerably more wear and tear and depreciation to the plates and life of the battery, result from over-charging than from under-charging, or any other cause. Over-charging not only has the effect of peroxidizing the positive plates and tending to rot the metallic support for the active material, but also very quickly necessitates topping up the cells with distilled water, a job which has not become any less troublesome in view of the location of the battery nowadays, mostly within the chassis frame. Over-charging has a further undesirable effect, in that the normal voltage on open circuit of our six cells, i.e., 12 volts, can be as high as 18 volts where an owner has allowed his battery to become more and more charged and has not made use of the one position on our Phantom switchbox enabling the car to run without charging. These large variations of voltage have been fully recognised to be highly undesirable, not only do they make the provision of suitable lamps very difficult (lamps becoming either completely blackened if of the correct voltage, or giving insufficient light if of incorrect voltage rating) but also an unnecessarily large ignition current is passed through the primary winding of the coil, which tends to increase any difficulties which may exist in respect of wear and tear to make-and-break contacts. In order to deal with the above condition of things, we are making a type of dynamo in which the characteristic curve of voltage provides for gradually lower output as the speed of the machine is increased, but as long as it depends upon the driver's initiative to charge his battery or not, as he likes, there is bound to be an amount of trouble and dissatisfaction. I suggest that it may be well worth our while to devise and make a simple form of automatic volt-operated- cutout which shall without any action on the driver's part at all, prevent any continued charge after the voltage per cell has amounted to, say, 2.3. I feel convinced that by doing this we should be saving a considerable amount of trouble, criticism and expense. Contd. | ||